Alternator/field duty signal wire/PCM problem

[flap00]

Ok...hoping someone with more knowledge of the charging system can help me out with some advice on this. Was driving along, minding my own business, and suddenly, the dreaded "Battery Not Charging" alert flashes in my dash. Limped home. Had a gut feeling that the alternator wasn't to blame, but after a bunch of rudimantary meter tests, I went and bought one anyway...ToughOne 150 amp from Advance Auto Parts. Installed it. (That bottom bolt is kind of a bitch!) Same deal...no charging. Did MORE rudimentary meter checks. Incidentally, no codes relating to electrical came up in my Torque app either. I read the schematics. Then I pulled the "generator field duty cycle signal" wire (gray) out of the plug, and reattached to the alternator, now with just the "generator turn on signal" wire (red) attached. Now it charges (although the dash still says "battery not charging" of course...as it's supposed to when something is up with that circuit). I did check the field duty wire, and it in itself seems fine....has continuity end to end when disconnected at both the alternator and pcm, and when connected to the pcm, it reads to ground.

Question 1:
Am I correct in my hypothesis that I need a new PCM...?

Question 2:
Also, since I have been meaning to get a tuned PCM anyway, my plan is to order one (using their core program), and that should hopefully solve this problem, as well as improve on some other stuff, right?

Question 3:
Since Black Bear Performance (who does not do phone calls whatsoever) apparently takes several days to even respond to all email inquiries, and then several more to provide and ship a tuned PCM to me...Am I ok to run the engine and drive around without that wire connected, or do I risk damage to something by doing that?

Thanks in advance for any help!

 

[BigEagle]

Hello, I don't know what your problem is but I agree in that the alt bolt on the bottom is a bear. I changed my alt recently and experienced the same charging levels as before (saw the batt guage go up and down at will and bright and dim lights.) Found on other threads that that pcm control the alt output for different conditions.

A new pcm, not sure. Is there anything else not working?

Never heard of Black Bear but if won't return calls/e-mails then they won't help with troubles you might have in future with thier products. I'm looking at PCM of NC.

 

[Mounce]

I'm also of little help but I definitely wouldn't deal with Black Bear. Customer service should be top priority and you'd be up a creek without a paddle for a few days if you had issues with the tuned PCM if something didn't act right.

 

[IllogicTC]

We have two PCM tuning guys around here we're confident with. One is PCMofNC, which maintains a professional presence around here and has had many happy customers who come here. The other is lime-swap, the owner being limequat, who maintains a presence around here also and has a very good knowledge of the PCM and may be able to help with diagnosis before getting a new PCM.

The PCM has a "watchdog" and is able to detect some problems within itself and set a MIL, however of course not all problems may be caught or reported.

 

[coolasice]

Does yours have a gbcm on the negative battery cable? Did ypou check continuity of both field control and sense wires(turn on)? Can you check voltage at the red turn on wire?

 

[AtlWrk]

It is possible (albeit extremely rare) to have an electrical failure within the PCM. If you plan on getting a tuned PCM anyway you're not really losing anything there.

That being said, my money is still on a wiring/connector issue. Intermittent connections are particularly tricky and may not show up when you have things disconnected. One last check I would do is to follow the gray field duty signal as close to the PCM and probe it (a straight pin just through the insulation works well for this, put a touch of nail polish or super glue on the hole when you're done so the wire doesn't corrode later). See if you get anything other ground when the alternator is running (use AC voltage mode on your DMM).

Also, what is the terminal voltage of your battery with the engine on and off?
What does Torque report your system voltage as?

 

[flap00]

Ok, thanks, dudes. I just ordered from PCM Of NC. That was my original plan, but I had happened to come across some really good reviews of Black Bear the other night, and was temporarily strayed. Actually, I just now ordered TWO pcms from PCM of NC...one for each of my '06 TB's.

So to address some of the questions & comments...

-BigEagle:
I've had either normal charging (with that wire disconnected), or no charging. Have NOT experienced any in-between, dimming lights, etc.

-coolasice:
Sorry, but what does GBCM stand for? Negative battery cable seems fine, for what it's worth.
Yes, the "red turn-on wire" shows around 5 volts a few seconds after starting the engine, just as I've read it should.

-AtlWrk:
Exactly. I've been trying for a while now to get around to ordering a tuned pcm anyway, so hopefully nothing to lose....and hopefully this fixes the charging problem too, of course.
I'll do what you recommended and double check my readings, but as far as I can tell, those 2 wires are fine as far as continuity, nor being grounded anywhere...except the grey field wire which is grounded internally in the PCM when connected to it. It does not have continuity to chassis/battery ground, though...even when it IS plugged into the PCM....hence, like I said...internally grounded in there.

Thanks so much for everyone's replies and advice so far....Keep it coming if anything to add, please!
I'm still wondering and hoping it's safe to be driving around with that field wire disconnected...

 

[coolasice]

Ok, thanks, dudes. I just ordered from PCM Of NC. That was my original plan, but I had happened to come across some really good reviews of Black Bear the other night, and was temporarily strayed. Actually, I just now ordered TWO pcms from PCM of NC...one for each of my '06 TB's.

So to address some of the questions & comments...

-BigEagle:
I've had either normal charging (with that wire disconnected), or no charging. Have NOT experienced any in-between, dimming lights, etc.

-coolasice:
Sorry, but what does GBCM stand for? Negative battery cable seems fine, for what it's worth.
Yes, the "red turn-on wire" shows around 5 volts a few seconds after starting the engine, just as I've read it should.

-AtlWrk:
Exactly. I've been trying for a while now to get around to ordering a tuned pcm anyway, so hopefully nothing to lose....and hopefully this fixes the charging problem too, of course.
I'll do what you recommended and double check my readings, but as far as I can tell, those 2 wires are fine as far as continuity, nor being grounded anywhere...except the grey field wire which is grounded internally in the PCM when connected to it. It does not have continuity to chassis/battery ground, though...even when it IS plugged into the PCM....hence, like I said...internally grounded in there.

Thanks so much for everyone's replies and advice so far....Keep it coming if anything to add, please!
I'm still wondering and hoping it's safe to be driving around with that field wire disconnected...

I don't think 06 had the gbcm so no worries there (it would be a module attached to the ground at the battery)

You can drive with field disconnected but the alternator will be on full tilt the whole time. When the field wire has open circuit it forces full output from alternator.

The field duty cycle is controlled via the pcm and is a pwm signal.

 

[flap00]

Right, so it shouldn't fry anything, due to the voltage being regulated either way. I mean, our alternators/generators didn't even have any restriction from pulse modulation in older vehicles. It's basically an efficiency thing, right?

 

[coolasice]

Yes, but you do run the risk of overcharging the battery (boiling the water).

 

[coolasice]

A good scanner(tech2) can tell you what the duty cycle being commanded is and a scope can verify (both of which are not cheap items). With a tech2 you can also command the duty cycle full on/off and verify if the pcm is working properly.

 

[IllogicTC]

While not as in-depth as a scope, a $50 multimeter which has frequency/duty cycle measurement can tell you what is being commanded, though you wouldn't be able to see odd waveforms, for example.

 

[coolasice]

While not as in-depth as a scope, a $50 multimeter which has frequency/duty cycle measurement can tell you what is being commanded, though you wouldn't be able to see odd waveforms, for example.

Won't find a dmm under 100 that can read duty cycle... Even my dads $150 fluke couldn't read that, only freq.

 

[AtlWrk]

IIRC the field duty cycle is a status line, not a control line.

The alternator's regulator is merely reporting to the PCM what duty cycle it is running at (which is an indirect measure of how hard the alternator is working/amps it's generating). As long as your alternator's regulator is working correctly (i.e. you're seeing normal system voltage) it can't damage your electrical system or battery.

The "generator turn on" signal is what gives the PCM control over the alternator though this is a simple on/off control to allow the PCM to inhibit the alternator at startup until the engine has stabilized.

 

[coolasice]

IIRC the field duty cycle is a status line, not a control line.

The alternator's regulator is merely reporting to the PCM what duty cycle it is running at (which is an indirect measure of how hard the alternator is working/amps it's generating). As long as your alternator's regulator is working correctly (i.e. you're seeing normal system voltage) it can't damage your electrical system or battery.

The "generator turn on" signal is what gives the PCM control over the alternator though this is a simple on/off control to allow the PCM to inhibit the alternator at startup until the engine has stabilized.

You are correct, disregard my previous statements. I'm getting new rvc systems confused with old

 

[coolasice]

Does the voltmeter gauge in the cluster read voltage or nothing?

 

[bobdec]

If I'm reading your 1st post it indicates you verified with a meter that "the battery is NOT charging when the GRY field wire is connected to the PCM, -and- the symptoms are the same on the old and new alternators". That indicates either .. the PCM is shutting off the alternator via the RED (L-Terminal)-OR- the alternator is internally shutting down whenever the GRY (F-Terminal) wire is connected. Is that statement correct ??

Also very strange there is no DTCP0622 the PCM checks that circuit when ignition is turned on. Before engine starts for a duty cycle near 0%, and after start when performing the alternator 'run test' for a duty cycle of 5-100%.

+1 on info mentioned previously, the field duty line is a read only field winding status the PCM uses to verify alternator is running correctly, no alternator controls involved. The actual voltage regulation is internal to the alternator, running w/o the connection will not effect charging.

If the alternator shuts off with GRY wire connected I would guess at three things 1-the GRY (F-Terminal) signal confusing the PCM into shutting down the red (L-Terminal). 2- The PCM code is screwed up (VERY,VERY rare) OR 3- the GRY F-Terminal circuit/wire is shorted to ground or a voltage (externally or internally in the PCM) and somehow messing up the alternator internal circuitry causing a shutdown. This can be isolated by 1 -using DVM to on red wire to see is PCM is turning off the alt when GRY is connected. If red level does not switch with GRY connected then PCM is not shutting down the alternator. Then 2- attach GRY wire at alt but not to PCM to check for shorts in harness. if alt stays on then short is probably in PCM, verfy by connecting GRY to PCM and see if alt still shuts down. ( note, for ref.. alt shut down is below 12.5 volts at batt when running , alt on is above 13.2 volts).

-- As a sidebar I'd get it scanned at an auto parts store to verify no DTC's, Torque is a good app but very gineric and sometimes not 100% accurate.. If truly no DTC's then the PCM becomes more suspicious..

 

[flap00]

Does the voltmeter gauge in the cluster read voltage or nothing?

It reads fine (over 14V) when the duty cycle wire is unhooked from the alt. It reads battery voltage of about 12V or so if I hook the duty cycle wire back up, and the alternator is not charging.

 

[flap00]

If I'm reading your 1st post it indicates you verified with a meter that "the battery is NOT charging when the GRY field wire is connected to the PCM, -and- the symptoms are the same on the old and new alternators". That indicates either .. the PCM is shutting off the alternator via the RED (L-Terminal)-OR- the alternator is internally shutting down whenever the GRY (F-Terminal) wire is connected. Is that statement correct ??

That is correct.

Thanks for the pointers, Bob. Will perform those tests soon as I can. It's been super cold here in NJ the past few days, so it's been tough to get out there to do much.

~flap

 

[flap00]

Well, now it won't put out a charge no matter what I try. I've tried 2 alternators, 2 pcm's, re-ran new signal and field cycle wires. Not sure what to try next...

 

[Mooseman]

Just a hunch, bring both alternators to Advance and have them tested. Who knows, maybe your original died and you got a dud from Advance. It happens. I got a bad reman from ACDelco once, right out of the box.

 

[IllogicTC]

Just a hunch, bring both alternators to Advance and have them tested. Who knows, maybe your original died and you got a dud from Advance. It happens. I got a bad reman from ACDelco once, right out of the box.

I support this. DOA parts do happen.

And for anyone needing a meter that can read duty cycle for troubleshooting this or other problems, $60 at Lowe's got me one.

Question though: What if one or both alternators check out okay? (and let's assume Advance's machine is working right, my neighbor took an alt up once and the machine said it checked out but it turned out to be bad anyway)

 

[flap00]

Oh, I wouldn't doubt it. Those yahoos in Advance couldn't even figure out how to mount the alternator to the machine. I had to worm my way past them and figure it out.

If you're happy with the one from Lowes, maybe I'll go ahead and grab one. Sperry? Fluke?...Sanwa..?

 

[wiredawg]

Hey folks, I need some help here, wondering if my problem below is in any way related to the discussion above;
Vehicle>2003 Envoy XL 4.2L/6cyl

Main Problem>charging system not working, "battery light" on & "battery not charging" on DIC.

Fix actions>Have old alternator and Battery tested at Autozone. Alt fails (no surprise, never been replaced). Battery overheating (again, no surprise no name battery about 4 yrs old. Purchased new alt &bat, additional item needed was the 2-wire harness plug, one wire broke off at connector while unplugging it from alternator.

-Install items like clockwork...no real issues, other than pain in the butt bottom bolt to secure alternator.
--Turn on engine: loud squeal, sounds like mis-aligned serpentine belt.
--Dash still indicates "no battery charge", check meter across "pos & neg" posts, reads 12.6...not good...Stop engine
--Metered across "alt case housing" and "positive battery post"...reads 12.66vdc and also check with power-on lamp tester...lights up brightly.
--Removed new Alternator had it tested at 3 different place (2 autozones & an advanced auto) it test fine.
--Note: today, I figured out the squealing is coming from the new alternator.
--Re-installed alt and started it squeals and doesn't stop squealing...turned-off
--Removed 2-wire plug, started vehicle; slight squeal for about 3 sec then normal...turned off.
--Returned plug...started vehicle...squeal again...this time removed plug while vehicle is running, squeal gone. So, I know what is squealing, just don't know why?

-2-wire harness. The only anomaly I can find in researching alternator issues. Everything else seems spot on for the alternator to function correctly.?.?.?
--So, In the key-off/no key position, I have a constant 12+VDC on both pins when measured against the positive post on the battery:
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead" to pin of red-wire) 12.62vdc This is okay, constant on...right?
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead to pin of "grey-wire) 12.72vdc There should "NOT" be voltage on this wire/lead in no-key position...right?

I pulled the PCM cabling and tested for continuity:
-Both the red and grey wires tested fine to the pins holes to cabling on the diagram provided.
-Also, tested for shorts and could not find any between wires.
-I also tested for voltage on the corresponding male pins protruding from the "PCM"? And I have the 12vdc there on both the red corresponding & grey corresponding pins!!! I think its safe to my problem is not in the cabling or harness??? But, now what??? "PCM" issue???

 

[budwich]

as I indicated in the other thread, you need to measure the red lead in the connector with key ON. That will tell you if the pcm drive circuit has some degree of integrity.

Having said that, the alternator making significant squealing sound when connected isn't good. When you say you had it tested, was it load tested or just "bench" tested (ie. not turning).

 

[wiredawg]

Hello all, I finally find some info going beyond the replacement of alternator & battery so summary of my problem below:
Vehicle>>>2003 Envoy XL (4.2L/6cyl)

Main Problem>charging system not working "battery light" on & "battery not charging" on DIC.

Fix actions> Tested alternator and Battery at Autozone. Alt fails...no surprise, never been replaced. Battery overheating...again, no surprise...no name battery about 4 yrs old. Purchased new alt & bat, additional item needed was the 2-wire harness plug, one wire(red) broke off at connector while unplugging it from alternator.

-Install items like clockwork...no real issues, other than pain in the butt bottom alternator bolt.
--Turn on engine: loud squeal, sounds like mis-aligned serpentine belt.
--Dash still indicates "no battery charge", check meter across "pos & neg" posts, reads 12.6...not good...Stop engine
--Metered across "alt case housing" and "positive battery post"...reads 12.66vdc and also check with power-on lamp tester...lights up brightly.
--Removed new Alternator had it tested at 3 different place (2 autozones & an advanced auto) it tests fine.
--Note: today, I figured out the squealing is coming from the new alternator.
--Re-installed alt and started it squeals and doesn't stop squealing...turned-off
--Removed 2-wire plug from alternator, started vehicle; slight squeal for about 3 sec then normal...turned off.
--Returned 2-wire plug to alternator...started vehicle...squeal again...this time removed plug while vehicle is running, squeal gone. So, I know what is squealing, just don't know why?

-Power questions regarding the 2-wire harness. The only anomaly I can find in researching alternator issues. Everything else seems spot on for the alternator to function correctly.?.?.?
--So, In the key-off/no key position, I have a constant 12+VDC on both pins when measured against the positive post on the battery:
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead" to pin of "red"-wire(Generator-on signal) 12.62vdc This is okay, constant on...right?
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead" to pin of "grey"-wire(Field Duty Cycle signal) 12.72vdc There should "NOT" be voltage on this wire/lead in no-key position...right?
--Also, tested voltage while running both red & grey leads reads: 7.23vdc
--And tested directly across red and grey leads while running and it read: 5vdc even....
[SIZE=13.3333330154419px]--Started pulling back the loom plastic covering attached to the harness and didn't find any visible signs of a shorted wiring. [/SIZE]
-- decided to check shorts/continuity at PCM cabling. Generator-on (plug nearest fan/pin2):Field Duty (middle plug/pin51)
-Both the red and grey wires tested fine for continuity to the pin-holes on cabling.
-Also, tested for shorts and could not find any on both grey and red wires.
-Here's the interesting part; I tested for DC voltage on the corresponding male pins protruding from the "PCM"? And I have the 12+vdc on both the red corresponding & grey corresponding pins!!! I "think" its safe to assume my problem is "Not" in the cabling or harness??? But, now what??? "PCM" issue???

Side Note: found this forum after all the testing above:
-I have not tried disconnecting the grey lead (field signal) and seeing if my alt starts charging...just to see if it charges, will try this tomorrow. Hopefully, it doesn't squeal, like a stuck pig.
-GCBM??? Unknown, did not notice any module near battery ground...but, wasn't really looking it something like that. Since, I thought I went through all the standards continuity checks pertaining to battery and alternator installation and that seems all good. I will look around for something of the sort tomorrow.
- Will also, try to follow bobdec comment.

-So flap00, did you ever get to a fix action here. I still do not know what to do after all this. If it is the PCM, have no idea what my next move will be...not at all familiar with PCM...more research I guess.

 

[wiredawg]

as I indicated in the other thread, you need to measure the red lead in the connector with key ON. That will tell you if the pcm drive circuit has some degree of integrity.

Having said that, the alternator making significant squealing sound when connected isn't good. When you say you had it tested, was it load tested or just "bench" tested (ie. not turning).

Thx budwich for your taking the time to respond.
- Looking at my notes and I'm starting to confuse myself. But, I tested the red lead (generator-on signal) by-way-of; generator-on(red) wire attached to red multi-meter lead & blk multi-meter lead attached to battery positive post=(-12.62vdc) while running this same test results were=(-7.23) I'm pretty sure I test with blk multi-meter lead to negative battery post and got no reading key-off & key-on while engine running.

- As far alternator test, simply ask the folks at the both autozone's and advance auto to test it. It appears they put a belt on it and hook-up the module plug, but I was not standing over them. Inputted some info into their machine based on my vehicle model. I was informing about the squealing hoping someone had this exact problem hoping to have a solution.

- Gonna try to completely disconnect the "field-signal-duty" (grey) wire and reattach the plug and see if about the squeal and maybe I'll get lucky and see some charging of the battery. Found that info at the here:

http://gmtnation.com/forums/topic/12650-alternatorfield-duty-signal-wirepcm-problem/

Can you explain the part regarding "PCM drive circuit integrity." What should I get to confirm integrity?

 

[Mooseman]

It is quite possible that with no load, there is no squeal not stressing the bearings but with a good load, it'll scream. I've seen that happen but on an old alternator. Is yours new or rebuilt? What brand?

 

[budwich]

thanks for some of the "clarification".... but you need to be absolutely certain of your testing otherwise it isn't really going to help as the results will likely indicate a lot to you. Further, your testing needs to be "good technique". Voltages are "always" taken as a "reference" to "something" cause that's what it means a "potential above / below the reference".... the reference for you is a KNOWN GROUND.... not a UNKNOWN VOLTAGE (as in the positive terminal of a battery) ....

Anyways, you need to do the "KEY ON, motor off" test with the red lead in the connector (connector disconnected from the alternator). This will tell you a "direction to go" in your search for the cause... otherwise, you can just start randomly replacing things and hope you find the right thing... :-(

As others have mentioned, when the connector is connected and if the system is trying to do something, the alternator will be under load. This will highlight problems as mentioned like the bearings not being "quite right".
The noise in itself isn't necessarily an indication that the alternator isn't producing any energy (and likely not the cause of no energy) but is likely an indication of a potential failure in the spinning which will become a total failure down the road.

 

[wiredawg]

It is quite possible that with no load, there is no squeal not stressing the bearings but with a good load, it'll scream. I've seen that happen but on an old alternator. Is yours new or rebuilt? What brand?

It's brand new from Autozone's Durlast DL1921-16-4 (149.99) with core trade-in. Also, had it tested by Autozone & it appeared he attached a belt and inputted some figure regarding my vehicle type. Mind you, I was not hovering just watching from a distance.

 

[wiredawg]

thanks for some of the "clarification".... but you need to be absolutely certain of your testing otherwise it isn't really going to help as the results will likely indicate a lot to you. Further, your testing needs to be "good technique". Voltages are "always" taken as a "reference" to "something" cause that's what it means a "potential above / below the reference".... the reference for you is a KNOWN GROUND.... not a UNKNOWN VOLTAGE (as in the positive terminal of a battery) ....

Anyways, you need to do the "KEY ON, motor off" test with the red lead in the connector (connector disconnected from the alternator). This will tell you a "direction to go" in your search for the cause... otherwise, you can just start randomly replacing things and hope you find the right thing... :-(

As others have mentioned, when the connector is connected and if the system is trying to do something, the alternator will be under load. This will highlight problems as mentioned like the bearings not being "quite right".
The noise in itself isn't necessarily an indication that the alternator isn't producing any energy (and likely not the cause of no energy) but is likely an indication of a potential failure in the spinning which will become a total failure down the road.

Okay here it goes: probably repeating some things but i think this is more definitive info with some question at the end:
-No key in ignition with negative battery post "DISCONNECTED":
--Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to neg bat post=+12.52vdc
--Grey wire(field duty cycle) to meter "red-lead" & meter "blk-lead" to neg bat post=+12.62vdc

-No key in ignition with battery fully connected:
--Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to neg bat post=no reading (didn't include this info since there was no reading)

--Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to "+ battery post" = (-12.52vdc)...I know this is "NOT" standard measurement practice. But, it was the only reading I got at the time. I figured this info was better than nothing...guess, I was wrong...just confused folks. LOL

--Grey wire(field duty cycle) to meter "red-lead" & meter "blk-lead" to neg bat post=again, no reading

--Grey wire(field duty cycle) to meter "red-lead" & meter "blk-lead" to "+ battery post" = (-12.62vdc)

-Key-in/"not turned" same results as "battery fully connected" directly above

-Key-in/"turned to 1st accessory position"(1 click):
--Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to "neg battery post"=(+5.03vdc)
--Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to "pos battery post"=(-7.31vdc, just thought I'd include this)

--Grey wire(field duty cycle) to meter "red-lead" & meter "blk-lead" to "- battery post" =no reading

-Key-in/"turned to 2d accessory position"(2 clicks): same readings as 1st accessory position.

And to clarify I have good voltage readings from positive battery post to alternator casing and chassis ground +12.6vdc or so.

-Started vehicle same results: loud squealing from new alternator and no voltage change across battery post reading about 12.5vdc-12.4vdc
--I disconnect grey wire(spliced) while still running; still squealing and no voltage change across battery.
--I disconnect red wire(spliced) while still running: squealing stops and there is some engine load difference, a noticeable pause or load difference within the engine. (not sure how to describe it) but it was like turning an accessory on or off. Obviously, it was the alternator.

So my last thought was to reverse my harness wires...I have reviewed my wiring hook-up at least 10 times now and I can say with confidence it is hooked-up as if the old alternator was in it. I compare my old broken harness and I simulated very thing.

But here's my new question: If my voltage readings are accurate...as far as I can tell in research forums. I have a diagram of pins outs for the field duty cycle (grey wire) and generator-on(red wire):

-I physically traced the red-wire(generator-on) to cable3(closet to fan)/pin2: tested continuity...seems to be no issue.

-Also, I physically traced the grey-wire(field duty cycle) to cable 2 (middle cable/pin51: tested continuity...seems to be no issue

-I have a diagram of the 2-wire clip, it matches the orginial broken one I have...

So, if my voltages are corrected;
What if I simply reverse the red and grey wires on the harness?
Is it possible the wiring inside the alternator is reversed and I have the generator-on from vehicle going to field duty inside the alternator and vice-visa?
Could this be causing my squealing?
Do I risk some electrical damage, if I try this?

Again, thanks for taking the time.

 

[Mooseman]

I say your new alternator is borked. While it may work on the tester, it may fail at higher real engine speeds. The fact that it squeals supports that. Your old alternator was fine until it died but this new one being bad is a coincidence. You can return it on warranty and get another one just on the squealing.

 

[budwich]

you are doing too much... lots of readings doesn't mean much if they are somewhat "helterskelter".

Anyways, the reading of the red wire to ground is good although maybe a bit high.
"Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to "neg battery post"=(+5.03vdc)"

BUT.... your descriptions of the wiring "scares" me. You mention "splice wire" with respect to red and gray. These are connectorized ... right?

Further, there are three wires going to your alternator... right? You don't seem to mention this at all. The "other red" wire is THE wire that "powers" your battery. IF its not there, you have a problem. Hopefully, I misunderstand your testing and results.

DON"T swap the "connectorized red" and "connectorized grey" unless you want to do some other trouble shooting of the PCM... :-(

 

[wiredawg]

you are doing too much... lots of readings doesn't mean much if they are somewhat "helterskelter".

Anyways, the reading of the red wire to ground is good although maybe a bit high.
"Red wire(generator-on) to meter "red-lead" & meter "blk-lead" to "neg battery post"=(+5.03vdc)"

BUT.... your descriptions of the wiring "scares" me. You mention "splice wire" with respect to red and gray. These are connectorized ... right?

Further, there are three wires going to your alternator... right? You don't seem to mention this at all. The "other red" wire is THE wire that "powers" your battery. IF its not there, you have a problem. Hopefully, I misunderstand your testing and results.

DON"T swap the "connectorized red" and "connectorized grey" unless you want to do some other trouble shooting of the PCM... :-(

-"Splice" simply means, I cut the wires since the pigtail is fairly long made it much easier for trouble shooting. So instead of constantly unplugging the connector (connectorized) I can just separate the wires at my splice point. And yes I keep them insulated. Once I figure this out, I will make a permanent splice.
-Yes a total of 3 wires; the positive large gauge cable to positive battery post via fuse box, attached to alternator via nut and bolt. Reads 12.6vdc or so against negative battery post and chassis ground. And the 2 signal wires.

Okay, so bottom line don't swap signal wires. I will remove alternator and get a replacement and will report back, once the 2d new alt is installed. thx all.

 

[flap00]

Ya know what?... I did get a stroke of bad luck with getting a bum alternator right out of the box, but the main problem, believe it or not, was the damn connector. I'd look at it, swear it was fine, plugged it off and on a LOT of times during that process. It was fooling me. It was just not making good connection most of the time. I finally happened to wiggle it just right, and I saw (in the elaborate mirror system I had set up on the driver's seat...lol) the volt meter finally bumped up. So, I stuck a paper clip in it to wedge it just right, and it stayed charging just fine...back to normal. I then proceeded to order a new connector pigtail from rockauto, swapped that in, and good to go ever since. I went through sooo much testing, alternator swapping, etc, etc... Damn it was cold and icy out when I was going through all that. It's hot as hell now...

 

[Mooseman]

Although not on this platform, I had a seemingly failed alternator. All of a sudden, it stopped. Start taking it off and I notice that the connector was off and not completely in. Put it back on and later on, it did it again. The connector's clip just wasn't making a good click. I trimmed the end of the connector so it would go in a little deeper and it clicked.

 

[wiredawg]

Hello all, I finally find some info going beyond the replacement of alternator & battery so summary of my problem below:
Vehicle>>>2003 Envoy XL (4.2L/6cyl)

Main Problem>charging system not working "battery light" on & "battery not charging" on DIC.

Fix actions> Tested alternator and Battery at Autozone. Alt fails...no surprise, never been replaced. Battery overheating...again, no surprise...no name battery about 4 yrs old. Purchased new alt & bat, additional item needed was the 2-wire harness plug, one wire(red) broke off at connector while unplugging it from alternator.

-Install items like clockwork...no real issues, other than pain in the butt bottom alternator bolt.
--Turn on engine: loud squeal, sounds like mis-aligned serpentine belt.
--Dash still indicates "no battery charge", check meter across "pos & neg" posts, reads 12.6...not good...Stop engine
--Metered across "alt case housing" and "positive battery post"...reads 12.66vdc and also check with power-on lamp tester...lights up brightly.
--Removed new Alternator had it tested at 3 different place (2 autozones & an advanced auto) it tests fine.
--Note: today, I figured out the squealing is coming from the new alternator.
--Re-installed alt and started it squeals and doesn't stop squealing...turned-off
--Removed 2-wire plug from alternator, started vehicle; slight squeal for about 3 sec then normal...turned off.
--Returned 2-wire plug to alternator...started vehicle...squeal again...this time removed plug while vehicle is running, squeal gone. So, I know what is squealing, just don't know why?

-Power questions regarding the 2-wire harness. The only anomaly I can find in researching alternator issues. Everything else seems spot on for the alternator to function correctly.?.?.?
--So, In the key-off/no key position, I have a constant 12+VDC on both pins when measured against the positive post on the battery:
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead" to pin of "red"-wire(Generator-on signal) 12.62vdc This is okay, constant on...right?
--Multi-meter "red-lead" to "positive post" of battery & multi-meter "blk-lead" to pin of "grey"-wire(Field Duty Cycle signal) 12.72vdc There should "NOT" be voltage on this wire/lead in no-key position...right?
--Also, tested voltage while running both red & grey leads reads: 7.23vdc
--And tested directly across red and grey leads while running and it read: 5vdc even....
[SIZE=13.3333330154419px]--Started pulling back the loom plastic covering attached to the harness and didn't find any visible signs of a shorted wiring. [/SIZE]
-- decided to check shorts/continuity at PCM cabling. Generator-on (plug nearest fan/pin2):Field Duty (middle plug/pin51)
-Both the red and grey wires tested fine for continuity to the pin-holes on cabling.
-Also, tested for shorts and could not find any on both grey and red wires.
-Here's the interesting part; I tested for DC voltage on the corresponding male pins protruding from the "PCM"? And I have the 12+vdc on both the red corresponding & grey corresponding pins!!! I "think" its safe to assume my problem is "Not" in the cabling or harness??? But, now what??? "PCM" issue???

Side Note: found this forum after all the testing above:
-I have not tried disconnecting the grey lead (field signal) and seeing if my alt starts charging...just to see if it charges, will try this tomorrow. Hopefully, it doesn't squeal, like a stuck pig.
-GCBM??? Unknown, did not notice any module near battery ground...but, wasn't really looking it something like that. Since, I thought I went through all the standards continuity checks pertaining to battery and alternator installation and that seems all good. I will look around for something of the sort tomorrow.
- Will also, try to follow bobdec comment.

-So flap00, did you ever get to a fix action here. I still do not know what to do after all this. If it is the PCM, have no idea what my next move will be...not at all familiar with PCM...more research I guess.

Hey all, just wanted to this thread know, at the end of the day. It end up being a faulty "New" alternator. Got a replacement today popped it in and wham...everything is good in my Envoy world.

 

[wiredawg]

-"Splice" simply means, I cut the wires since the pigtail is fairly long made it much easier for trouble shooting. So instead of constantly unplugging the connector (connectorized) I can just separate the wires at my splice point. And yes I keep them insulated. Once I figure this out, I will make a permanent splice.
-Yes a total of 3 wires; the positive large gauge cable to positive battery post via fuse box, attached to alternator via nut and bolt. Reads 12.6vdc or so against negative battery post and chassis ground. And the 2 signal wires.

Okay, so bottom line don't swap signal wires. I will remove alternator and get a replacement and will report back, once the 2d new alt is installed. thx all.

Hey folks at the end of the day. It ended up being a "Borked", as Moosman would call it, "'New'-Alternator". I went back today and explained to problem..this sale associated showed some concern and said he never ran into this type of symptom. He tried to replicate the problem on the bench. And he did say the test is suppose to mimic a load while testing. Anywho, he could not get it to squeal but the performance was shaky. Passed then fail, Pass then fail...was trying to get it to squeal. I had to give him my "I'm not lying face." LOL...he gave me a replacement, same brand/model. Installed it, as I done about 3 previous times, and we are off-to-the-races. All the bells and whistles. Took all the measurements and they were spot on. Hell..personally, I think its purring like a kitten...(cleaned the throttle-body, 1st week of June) So, in the end it was a bad "new, off-the-shelf" alternator. But, I wish it would have squealed, just to make me feel better. The good news...all my voltages above the previous post are correct. So, there's at least a base-line for someone not so-familiar with "Alternators" and those 2 signals wires, as I was; Grey:field-duty cycle & Red:generator-on signal. Hell, I even know where they go on the PCM plugs...LOL Anywho, thanks all for taking the time to respond with your collective guidance. I was feeling so good after this victory, I dusted off my soldering iron and took on the "stepper-motors" in the instrument panel, replaced all 6. I ordered them from Amazon about about a month ago, but the Envoy was rarely home, when I was here. Got it done in a couple of hours and now the dash to registering proper RPM's, fuel, oil pressure & Temp...Started acting up about 6 months ago. I guess its not bad for a 2003.

 

[Mounce]

Awesome, thanks for reporting back. Might help someone in the future if they have the same problem and stumble across this thread.

 

[Mooseman]

Just goes to prove that:

1. New parts can be bad
2. Don't always trust parts store testers or employees who do the tests.