SOLVED! Stalling and rpm jumping

S13Hitman

Well-Known Member
#1
02 TB i6
Already replaced ign switch, clean throttle, cpas. And the fuse box.
Truck was given to me from a friend who owned it for 10 years and replaced the tranny 3 times. Kept great maintenance and minimal issues.
Over a few years I keep having these reoccurring issues and don't know if they're related. I've had a shop fix it each time which said the wiring was damaged behind the fuse box.
The issues started happening only at 55-60 when the ABS light would come on, followed by the rps jumping from 1500-2000 ish. It would stop at first but then it would stall after the first few times of the rpm and ABS issue. The truck would stall, it starts back up without a code and then a few miles later or less it stalls again.

Now its doing it again. I got a code 2 days ago for p0013. Ive replaced this part twice for the code coming up before.
This time i took a look at the wiring myself and found at some point, someone ran a direct new wire for the CPAS straight to the ECM. I found the original brown wire disconnected, also found that the new CPAS wire and the ground had both been poorly wrapprd with open wires (both CPAS wires) that seemed to be touching when it was unwrapped. Not good so i cleaned them up and checked continuity for the new CPAS wire and it checked out fine. No code for 2 days for that sensor or wiring.
Then today, no code but the truck stalled 3 times on the way to work. Wtf please direct me where to start? I don't see any bad wiring in the harness behind the fuse panel.

My to do list to check so far, please impute advice, is to check the IAT sensor and if that checks out fine possibly pull the tranny pan and test the TCC. Found a nice video on how to diagnose that sensor.

Im just bad with knowing how to use a multimeter well and where to find needed circuits. What else could be causing my issues? How does this issue keep happening every 3 to 4 months...

FYI, the original owner had an aftermarket intake installed and the IAT sensor could possibly be jacked up. this would be the easiest fix but doesn't really explain why the ABS light would come on.
 
#2
I doubt the IAT would cause it to stall since all it does is report intake air temperature and would throw a code if defective or not reporting properly.

With previous shoddy electrical by the PO, I'd be checking everything for more. Other than that, I'd be looking at the fuel pressure. The pump might be intermittently failing and causing the stall.

For the ABS, you would need the code for the error. If you get a Bluetooth OBD adapter and the Car Gauge Pro app, you could read those codes and also use Torque to read live engine data, which could also help in diagnosing the stalls.
 
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S13Hitman

Well-Known Member
#3
Ok thanks Mooseman. I do have a scanner but only have the torque light version. I just found out i need the paid version so I will download those and give it a shot.
 
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S13Hitman

Well-Known Member
#4
Ok i drove around a bit without having an issue until last minute of driving. Should be logged as i had it setup to the best of my abilities... now i just need to figure out how to share the info for all to look at. Hopefully its helpful

The only issue was just a stall and now no start. No codes... :sadcry:
 
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S13Hitman

Well-Known Member
#5
My local pull a part always has plenty of TB and envoys. Im thinking about just pulling a wire harness. Does the engine bay wiring harness go through the firewall like in my old 240sx? I think they may be seperate which wouldn't be too difficult to pull it then.
LKQ just received 2 TBs this week that are 02 and 03.
Thoughts? The wire gremlins in this harness just keeps coming up and ive spent a lot of money chasing it.
 

MRRSM

Lifetime VIP Supporter
#6
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S13Hitman

Well-Known Member
#7
Just an update on issue, stalls intermittently and no crank. Seems I keep having wiring breaks and/or short(s).

Okay guys I'm reaching out for guidance on checking my Ignition E circuit. In following a few videos I was able to narrow things down to IGN E but need some help on where to dig. I have no power at that circuit and makes sense for the no start when looking at the wiring diagram.

Please guide or confirm:
It looks like, at least to me, that I should be checking the YEL/BLK signal wire and the DK GRN coming from the PCM. I'll check continuity and then for 12v while my wife attempts to start the truck. From there it gets a little confusing for me. I also don't have a layout of where the DRK GRN wire is coming/going from the PCM. I see 2x different numbers for that wire at the PCM, 1433 and 29. Which number is the pin and where is it?
 
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S13Hitman

Well-Known Member
#8
Wait, I may have misunderstood something. IGN E is hot only when the Key is in the RUN position. I just checked and got 12v when the key was turned.
I've unwrapped a lot of wire harness but to only check for previous work done and haven't found anything yet other than the CPAS wiring which hasn't given me trouble since and shouldn't have anything to do with current issues.
 

budwich

Well-Known Member
#9
wiring issues are never fun... specially if someone else did them... :smile:

look at this post for the schematic
https://gmtnation.com/forums/threads/2002-trailblazer-4-2l-no-crank.19025/

Further, your statement about "ign E is hot only when key is in RUN" is not correct, it is hot in start also.

Further because you are having multiple issues, try focus on only one at a time, chose wisely going for the one that is easiest to reproduce, and trace, if you can.

IF you can get to the "no-crank" one readily, as you have already done work in the area... when you get the instance, check the start relay or change it with another in the box. You can also remove the relay and check the electrical conditions during key on and key start to see if they are presented to the relay correctly. lastly, during your "no-crank", if you jump the contacts of the relay (see the diagram for the right ones) and the crank happens you know the problem is from the relay "back" as opposed to "forward" to the starter.
 
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S13Hitman

Well-Known Member
#11
Okay did some testing and the truck started while checking things. Stalled within a minute but started up again and ran for 5 mins. Doesn't help me while looking for a broken wire that is making contact again.

Some results from my test:
-When jumping the relay socket (pin 30 and 86) it does crank.
-fuse 28 checked out fine, someone said to look at that in another thread
-Have continuity from pin 30 on the relay to the starter, but noticed also when touching the starter solenoid housing (exterior). Is that correct?
-Red Ign wire at the ignition switch has 12v

NOW, when the truck just started while checking the ign switch yellow wire, the truck fired right up. I had put the starter relay back in just in case it made a continuity difference. While it was running I heard an intermittent click sound coming from the fuse box area, possibly the fuse box or a relay. It became more prevalent when moving the wire harness behind the fuse box around.
Sounds like I need to dig in more behind the fuse box but there's pretty much no slack in the wire harness to get a good look.

Any advice from the sound and my results are appreciated. I understand since it attempted to crank while jumping the relay pins that it's from the relay back. What does "back" refer to? Going from the fuse box into the cabin towards the ignition switch?
 
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S13Hitman

Well-Known Member
#12
Oh and without the starter relay in, I checked the yellow wire at the ignition while in the run position and had 12v. Had my wife wiggle the fuse box and wire harness to check for a drop. Nothing.
 
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S13Hitman

Well-Known Member
#13
The PPL wire going from the crank fuse to the PCM is not getting 12v when in the run or on position. I'm not sure how to separate the fuse box and look for any breaks in there but I'm suspecting the fuse box may be causing this as it was replaced before. I'm wondering if I can just run a new PPL wire and see what that does first. I'm not getting continuity from the PCM to the crank fuse, so my break must be in that wire or inside the fuse box.

Thoughts?
 
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S13Hitman

Well-Known Member
#15
I replied to you in the other thread.. Let me know what you think, I posted more info about the relay and what I've found. Its also my only set of wheels and need to figure this out now. Please let me know what you think, appreciate your time!
 
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S13Hitman

Well-Known Member
#16
So I'm still without the truck working without stalling but have been too busy to do much.
Update, took apart the fuse box and went through it with a magnifier, no breaks and looks really clean. Also replaced the fuel filter just because it was over due.

The truck still stalls after the ABS light comes on. I can drive a mile or 2 and it starts to sputter and then stalls. Sometimes starts back up now and sometimes doesn't until it sits for a few hours.

dad in-law suspects the fuel pump. How does the ABS light have anything to do with is really throws everything off but I'll be ordering an acdelco pump ASAP. I've seen SOME good reviews for another brand that's much cheaper but curious if anyone has tried those with positive reviews?
 
#17
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S13Hitman

Well-Known Member
#18
New Acdelco fuel pump installed. fuel filter and new Acdelco ignition switch. brand new oem starter relay.

fuel pressure is good. today I unhooked the battery for a few hours while i put the new switch in. started up and stalled right after a bunch of clicking noises coming from the engine bay near the PCM.

come on guys i need your help still. what else could be causing this stalling issue. i noticed the last few times while it stalled something was clicking like a switch engaging on and off.

could it be the EGR valve thats on the drivers side of the engine bay? thats the general area the clicking was coming from.

help... i cant stand not having wheels anymore.
 
#19
No EGR in these. Could be relays you hear or the fuel injectors.

Check all the grounds and electrical connections. The grounds on the lower driver side of the block would affect engine controls.
 

I_Shoot_Back

Well-Known Member
#20
do you have the radiator fan with the sensor connected? wires in the harness from that sensor to the connector can get damaged and pull down the 5 volt rail in the pcm.
The ticking sound made me think of that.
 
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S13Hitman

Well-Known Member
#21
I meant to say EVAP purge valve or anything having to do with that system. My first thought was a relay but couldn't tell for sure where the clicking noise was coming from. It seemed like it was closer to the engine than the fuse box area.

I'll try and work on the grounding straps today if I can find some time. While these stalling issues are going on, the front main seal finally gave way and is slowly leaking and seems to be slinging oil all over the front of the engine compartment.
 
#22
I merged your latest posts/thread with your previous one. Please continue with the same thread.

Have you rechecked for codes? When it's not stalling, how is it running? You should hook up a scanner or an OBD adapter with Torque to get data like fuel trims, MAP, O2 sensor voltages. Clicking could also be throttle body trying to keep the engine going. I've heard that when pulling the fuel pump relay to stall the engine on purpose.
 
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S13Hitman

Well-Known Member
#23
Yes i have an adapter pluged in, no codes at all. The truck runs normal right up until it stalls, seems like ignition cut, not really a sputter. It'll run for 3 or 4 mins before doing this. I here the clicking noise as well when its stalling.

I haven't been able to figure much of torque pro out and failed at data logging.

I used to get the ABS light coming on before these issues but that was only when driving around. i cant even leave my driveway now because it stalls so quickly now.

I have a day off tomorrow. Going to clean the TB even though I did so less than a year ago. Will also clean up a few grounding straps amd reset the PCM.
Then I'll try and mess with torque pro...
 
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S13Hitman

Well-Known Member
#24
UPDATE- Pretty sure I found my problem area and have a video to show/prove what I'm talking about. While I'm uploading the video and trying to share or attach it, I'll try to explain and hope you guys have some input.

Truck started just fine, once I moved the wire harness coming out of the last PCM's connector (closest to firewall) I was able to get the clicking noise to start. The truck stalled right away. After the truck stalled, I kept moving the wiring harness and I can hear the fuel pump turning on and off. I did un-tape that harness and didn't find any breaks or shorts yet but maybe you guys have some input here or have had this issue.

I started to get into the TB cleaning and noticed it was pretty clean from the last time I did it. Also took off the 2 grounding points on the driver's side frame and cleaned up the bolts, the metal and the terminal. Then sprayed it with some primer. No change.

Obviously I need to keep looking but I'll try to upload the video asap.
 

MRRSM

Lifetime VIP Supporter
#26
As for trying to hunt down Hidden Broken Harness Wires... Using THIS tool will make quick work of finding the break(s) and make your life easier:


...and here is another example of trying to sort out an Automotive Electrical Re-Wiring Nightmare using a similar device:


On the GROUND side of the issue... the Interior Cabin Body Ground at G201 is located along the Passenger Side Console under the Dash Panel and this Video done by our Redoubtable and Famous Member @MAY03LT will address how to ensure you are getting Good Grounds for a LOT of things on the Databus by ensuring a Properly Grounded Splice Pack screwed down to the inside of the Engine Firewall:


You will also need to View, Download, Save and PRINT OUT the PCM Harness Wiring to Pinout Diagrams I attached in Post #4 at THIS Link in order to be able to Diagnose WHICH Ignition Circuit Wires to investigate first... along with any others that might also be Hidden and Broken to know What The Hell this Bag of Snakes looks like in Plain View:

https://gmtnation.com/forums/threads/bcm-pinout.16994/
 
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#27
Very unusual. My old '02 I had replaced the engine, the PCM countless times, disconnected it numerous times for various reasons and never had an issue like that. Because of the shear number or wires in there, it may be worth it to just replace the whole harness.

I have seen Scanner Danner on YT diagnose a broken ignition signal wire to one of the coils so it is possible. In this case, we have no idea which wire.
 

MRRSM

Lifetime VIP Supporter
#28
I've watched your Video about a Dozen Times... and if it were me... Since you will have to do this anyway just to gain enough access to freely move the Harnesses around... I'd start by pulling the Power Distribution Center/Fuse Box completely off of the Fender Well Mount.

Then... Carefully remove and examine the Wire Harness Blocks, eyeballing the undersides where each Harness Wire inserts into those Plastic Blocks with a Bright Flashlight during this procedure for any obvious Loose, Burned or Broken Wires FIRST.

Look everything over along the length of the unwrapped Harnesses VERY CAREFULLY for anything that is even SLIGHTLY suspicious... I mean anything that looks like Burn Marks or even slight Smudges...or any obviously thinned out insulation areas and focus your attention there for anything that might just become that obvious. Take images of EVERYTHING so you can re-construct your dis-assembly->< - re-assembly steps in reverse if more than one of the wires accidentally come out of the Plastic Blocks.

You just might get very lucky and get the right one located from the start of your investigation. DO NOT RANDOMLY PULL ON ANY WIRES IN THE HARNESSES... You may damage something that is not yet FUBARed and as per "The Hippocratic Oath" for Mechanics ..."First... Do No Harm...".
 
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budwich

Well-Known Member
#29
Click here to watch stalling issue

Okay please take a look!
Interesting find... you are likely there ... but where is "there"... :smile:

It is strange that the vehicle doesn't die right away... so it is not a wire that "commands" an immediate shut down. Probably guess would be the fuel pump relay wire / control there of. One would have to look at what's in that connector (schematic) to whats of "interest".

Now that you know to cause the problem, depending on how fast you want to go at things, you can confirm by putting on a fuel pressure gage and then do your "move the cabling test" and see what you see. Further, "fuel supply" issues have very little / no fault codes that would register for the "check engine" light.

having said this, from all the wiring issues that you have come across, a "gross replacement" of at least that one PCM cable might the right direction... of course after inspecting its termination in the fuse box.

further... so much for my "fuel pump control" suggestion as a point of interest in the pcm cabling.... the bad news its on the 2nd connector... :-(

so my next guess would be "ign 1 voltage".... which is on the 3rd connector.
 
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S13Hitman

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#30
You guys are extremely helpful, thank you.

MRRSM - Thanks for linking that tool, I'm ordering that today as I won't have time for a few days to do much anyway with the truck. I didn't know MAY03LT was on this forum, never watched the ending of his videos but his videos are freaking awesome.
-I'll check that grounding point and sand it a little, make sure good metal to metal contact. I did print out those pin-out diagrams a few weeks ago.
-I removed the fuse box last week and dissected the thing. I'll remove it again and check over the plugs and keep it out while trying to find my "issue" wire. Good call and great advice, thank you!

Mooseman - I've been suspecting the wiring harness the whole time and even contemplated just swapping in another. Is the entire harness in the engine bay 1 piece or 2 pieces? I ask because I noticed on ebay where another harness didn't seem to have the PCM plugs attached.

Budwich - I'm leaning towards the purple wire coming from the fuel pump or a wire having to do with the fuel pump. Good call on puting a gauge in and then re-create the issue. Then I just re-read your post, damn I guess I'll just have to investigate, that wire tracker tool may be very helpful except that I believe I need to know the bad wire in order to use it and then trace to where it's broken. At least thats how I understand it.
 
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S13Hitman

Well-Known Member
#31
Quick question, I screwed this up before so just want to check. The 3 PCM connectors, is C1 closest to the firewall or C3? I think I assumed it was C3 the last time and was wrong.
 

MRRSM

Lifetime VIP Supporter
#32
THIS image is definitive about where those "Three Amigos" White, Gray, and Blue Connectors MUST be attached. Also... if you check out those Pin-Out Diagrams... I believe their C1, C2, C3 designations are also written out identifying each one BY COLOR ACRONYMS of NAT (Natural), GRY and BLU as well... Here you go:
,

1542067854555.png


GMPCEMHARNESSCONNECTIONS1.jpg


GMPCEMHARNESSCONNECTIONS.jpg
 
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#33
Mooseman - I've been suspecting the wiring harness the whole time and even contemplated just swapping in another. Is the entire harness in the engine bay 1 piece or 2 pieces? I ask because I noticed on ebay where another harness didn't seem to have the PCM plugs attached.
I believe it is. One for engine controls and another for electrical accessories. I'd go to a pick-n-pull and get one there.
 
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S13Hitman

Well-Known Member
#34
UPDATE - The Ign 1 voltage wire (pink) has a break somewhere near the little plug, see attached pics. This wire runs from the Blue PCM connector to the little plug. -Continuity was good but then I rigged up some wires to slide into the female ends and as soon as I moved the wiring harness around I started losing the connection.

The pink wire had some discoloration in 1 area but nothing else noticeable. It's a pretty short length thankfully.

I don't have any 22 gauge wire to replace it with on hand, only 18 gauge and I believe you can't switch those out. I'll have to wait a day or two until I can get to a store that carries 22 gauge.

Fyi, the zip-ties mark my areas where the tape changes directions or splits off.
 

Attachments

MRRSM

Lifetime VIP Supporter
#35
Great Job on Running this Animal to "Ground" !!! ... and props to @budwich as well for Dialing in on the IGN1 Circuit.

I completely agree with your decision to ONLY use the correct Type and AWG Automotive Wire for this kind of repair. THIS is THE Wire Bundle you want to get from Amazon:

https://www.amazon.com/dp/B01M0O1NXM/?tag=elightbars-20

AWG22WIREBUNDLE.jpg

... and Don't Forget to Slip the Heat Shrink sections along the free wire lengths of that Pink Wire FIRST... Before you begin to Solder in this Wire Segment!
 
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S13Hitman

Well-Known Member
#36
OMG I always forget to slide the heat shrink tubing on first and then have to cut the wire and start all over. Thanks for linking that for me and confirming not to use the 18g wire I have.

Praying this is my only issue wire. I should probably test the other wires in the same bundle before putting it all back together.
 
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S13Hitman

Well-Known Member
#37
SOLVED! If someone can update the title that would be helpful.

The little plug in post 34 had the ignition 1 (pink wire) wire barely making contact. I had to actually pull the pin out and solder a new wire to the pin as I had no space to solder without removing it. That plug comes off of the PCM's blue connector and runs down below the truck.

It would be best for me to get a used wiring harness and just replace the entire thing as mine seems to have a few issues and has been worked on previously as well.

Drove around all morning with no issues, finally...
 

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