Multiple codes

[Vale]

Please help.. I just got me a 05 trailblazer against my wife will , anyway I'm driving about 75 and I notice rpms higher than normal so I get home put on odb scanner and it reads 4 codes
P0785. P0740. P1810 and P2761. What the hell....

 

[Mooseman]

Here's a good place to start. Multiple transmission codes all at once are usually electrical in nature.

https://www.google.ca/search?newwin......0...1c.1.64.psy-ab..0.0.0....0.nN_EkkjHNAQ

 

[Vale]

So you believe it's electrical? From your mouth to God's ears cause my wife will kill me if I have to buy a transmission.

 

[mrrsm]

This problem must be getting contagious... there is another similar active posting on this very subject right now. The "Higher than usual RPM" sensation you felt probably came from the inability of the Transmission to shift into overdrive due to the Solenoids not receiving enough voltage. The first suspect among a few others, like broken wires or badly corroded grounding wires to and from the Transmission Wiring Circuit and Harness(s) is ...The Ignition Switch.

There are quite a few good "How To-s" for the R&R of the Switch here at GMT Nation... just be certain to try to find an OEM ACDelco Ignition Switch via NAPA or The Local GM Dealership rather than using any AA or AZ parts outlets due to frequent failures of their "new" Switches... and ...BEWARE of improperly installing the New OEM Switch by accidentally moving the Internal Gear Teeth from being a perfect match of position compared to the one that you remove from the bottom of the steering column. Visit Youtube for lots of Vidoes on "How to R&R The Ignition Switch in the Trailblazer Envoy, etc. as well.

 

[Sparky]

P0785 Transmission 3-2 Shift Solenoid
P0740 Torque Converter Clutch Circuit Malfunction
P1810 Transmission Fluid Pressure Valve Position Switch Circuit
P2761 Torque Converter Clutch Pressure Control Solenoid Valve Circuit


All those codes are electrical codes, so yeah, probably don't need a whole transmission but just figuring out the electrical problem. Likely a common source for the issue, like a bad fuse, broken wire, bad common ground, etc.

 

[Vale]

I really appreciate the responses that I'm getting and looking forward to getting home so that I can see if I find where the problem is at. 😔

I just spoke with the guy who sold me the truck and told me that he had done an engine swap on the truck 2 weeks before I got it could there be something there I mean it drove ok when I got it for a week then I went and got a new battery and I say a day or so is when this happen. Maybe ?

 

[Vale]

When you say a bad common ground? Where?

 

[mrrsm]

Check @Mooseman ‘s Signature Line in any of his Posts to find the Links to the FAQs and Specific Service Manuals. You will need to read and follow the advice on organizing your approach and not try to investigate everything all at once and get lost in the weeds B4 you can figure out what things to look at first , etc.

The best friend you have is a willingness to search GMT Nation archives and read more than one post on these problems and gauge your approach by weighing the facts and support you find while doing your research. In all probability... the answers are already there to similar questions that have been sorted out several times in the past.

If you change the Ignition Switch and that approach proves to be a solution after you have cleared the codes and find no repeats... then the exercise of that necessary action to answer each and every question before you have tried of even one of them... becomes academic.

 

[Vale]

Hello just wanted to ask if I may.? You answered on my multiple codes and finally I had time to look at it and checked on what you suggested and tested all fuses especially #47 and power good now i got under pulled plug from transmission and with truck off and truck on I was not able to get anything but maybe 00.8 . Want to know what next.?

 

[Vale]

my apologies I'm new to this.

 

[Sparky]

If you're not getting positive power at the plug, you've got a damaged/broken wire between fuse and that plug. My guess is the harness got pinched someplace when the engine was swapped, and it finally broke the wire. Try and follow the harness, looking for places it may be getting squeezed at. If you find that spot, then you have to do two things: Move it so it isn't pinched anymore (depending on why it is pinched will determine how easy or hard it is to fix that) and fix the wiring (both the broken wire and inspect the rest for any damage).

 

[Vale]

Just alittle ahead of myself, if i don't find a pinched cable what do think would be the next step?

 

[Sparky]

Well, if you have power at the source, but not at the destination, I'd make certain you're probing the correct wire. If that is certain and verified no juice, then you have to have a break in the wire someplace. Worst case, you replace the wire if you can't find the bad spot in it to fix. Maybe just that section of the harness (get a used one from a yard or something).

 

[Vale]

On the probing just to make sure I tried every pin hole with car on and off and got nothing close to 12v

 

[Vale]

Thank you I will try and look when I get home. Again thank you.

 

[mrrsm]

If you have a printer at work... make a few copies of this image as it will come in handy from time to time. This is the Pinout of the Round Connector on the 4L60E Transmission. If you can place your probe on the "E" Pin and check for Voltage with the Key ON... But NOT in Run ... if you get anything less than 12 VDC... Either the Wire feeding the Power On-Off Circuit there is Cut or Damaged or Loosely Grounded...or... The Ignition Switch is BAD and failing to connect power to the 4L60E via the Pink Wire that is feeding it and so it is NOT getting the full 12 VDC when the Key is Turned:

 

[mrrsm]

I am copy-pasting the PM Dialogue that the OP has been using to discuss the developments here that are not open to the view of the forum and requesting that he continue to do so over here:

Vale
Hello just wanted to ask if I may.? You answered on my multiple codes and finally I had time to look at it and checked on what you suggested and tested all fuses especially #47 and power good now i got under pulled plug from transmission and with truck off and truck on I was not able to get anything but maybe 00.8 . Want to know what next.?

MRRSM
See the Post for my response... No need to PM... It is Best to keep all of the running dialogue going in your Main Thread as that way... more people will be able to share the Diagnostic Analysis with you. The Pin-Out Image I posted there should help you to visualize the circuit better. If you need to see how to R&R the Ignition Switch... I'll post the proper links that have Videos showing the processes involved.

Vale
I have a dumb ? Can a wire be ran from the fuse to the transmission plug.?

MRRSM
Please do not continue to use PMs to discuss this matter... Bring it back over to your Original Thread. I am having problems with opening PMs on my computer... sometimes it works and they open up… sometimes they do not.. But... in any case.... All of this information needs to be covered in the Open Forum so there is no need to have any duplication or have any hidden responses not in the direct view of the larger GMTN Readership.

The short answer to your last question is Yes... as long as the wire being used can carry the Amperage and Current of the Fuse and the Voltage... you could temporarily by-pass the Ignition Circuit all together to get Un-Switched Power to the Round Connector. But first ...you would need confirm that you are reading 12 VDC on the out going side of the Fused Circuit coming out of the #47 Fuse before making this attempt. You must still realize that even by doing this Wire By-Pass … you will still NOT know whether or not the Ignition Switch is BAD ...or the wiring are BAD by doing this action..

 

[Vale]

Can I run a wire from #47 to the e pin since I'm not getting 12v the plug

 

[Reprise]

On edit - after seeing Mooseman's reply below, I'm removing my implied permission to bypass the wire.
See his post immediately after mine.

 

[Mooseman]

@Vale , I wouldn't bypass the wire like you suggested. If more than one wire is damaged or shorted, this could cause more problems than it could solve. Follow the advice given, test each wire following the schematics and see there is continuity to each of them. Report back once you obtain the results of these tests.

 

[Vale]

? Because I have 12v at fuse #47 does that make ignition switch good?

 

[Mooseman]

If the tranny only thing that is having electrical problems, I doubt it. If you are getting 12V at the fuse, then obviously there is an issue between it and the tranny plug.

 

[Vale]

What do you mean you doubt it? I've checked every fuse and all of them are good I've check that all had power to them I checked ignition switch i got under and unplugged the transmission plug checked voltage at E pin on the plug it self and nothing..what am I doing wrong am I not seeing or not checking something right?

 

[mrrsm]

You seem determined to completely side step the possibility that the real problem here... might well be The Ignition Switch. Take a Minute to review that Round Connector Pinout Diagram and look closely at what the E Pin tells you that is involved in its connection... it directs 12 VDC Power to the entire Transmssion Solenoid apparatus as a Switched On and Off control point...AND the Wire Color is PINK... just like the PINK wire in the Ignition Switch Harness...that either works when you turn the Ignition Key... or Fails to deliver a nice, refreshing dose of juice at 12VDC. If you ignore the possibility that the Ignition Switch is a candidate for an R&R ... then you will never escape the Diagnostic Loop you are presently stuck on.

“When the Student is Ready... The Teacher Emerges...”
Confucius

 

[Mooseman]

I'm not at home at the moment to look at the schematics but just going from memory, the fuse supplies 12v+ directly to the tranny after it's switched on by the ignition switch. The others are controlled by the PCM through negative switching or PWM signals.

I am going to contradict @MRRSM in that I still doubt it's the ignition switch. If it was, there would a lot more stuff not turning on like the ignition, PCM, etc. It would be very evident that a slew of circuits are not getting power. Just because there is a pink wire from the ignition switch doesn't actually mean all pink wires are powered by the ignition switch. If fuse 47 is getting power but the pin E at the plug isn't, there is a break somewhere you need to confirm, as well as test the other wires for continuity.

 

[mrrsm]

I also thought at first that all of the other feeds would go down if the Pink Wire Ignition Switch went sideways... but this article makes me think that a bad one might be the cause because of how complex the Ignition Switch Internals are that can get very sketchy:

https://www.justanswer.com/chevy/1ghlp-trailblazer-will-crank-codes-tranmission.html

To help work this idea out... this Ignition Switch to Transmission Wiring Diagram is for a 2005 Trailblazer... But I think the circuit is the same for the 2002 flavor:

 

[Mooseman]

But that's just it. He has power at fuse 47 but not at pin E so there is a break in between those two points and possibly others if the loom to the tranny is damaged. And if you notice right after the fuse, it feeds other circuits, hence there would be other stuff not working.

 

[mrrsm]

I cannot argue with that Perfect Logic... so perhaps that Fuse# 47 needs a Much Closer Look... and since @MAY03LT has done this video... perhaps it will help to move from the mystery into clarity...and also ...I am beginning to wonder if the Elephant in The Room is this Un-Asked Question:

"Do You Have any After-Market Remote Starter or Security Devices or ANYTHING like them wired into the Vehicle as Add-Ons?"

...and since ALL of the Shift Solenoids do work off of that One Wire 12 VDC Power Source serviced by Fuse #47... this TSB has some additional procedural things to follow up on that could prove helpful as well in running the damaged wire down:

https://ww2-secure.justanswer.com/u...evrolet_trailblazer_starts_in_third_tsb_1.pdf

And this 4l60e Transmission Solenoid Power Circuit Schematic seems to match the one Drew (@MAY03LT) was using in his video:



It also follows that if the OP intends to get under the truck to examine the Wire Harness locations for possible wear and tear, cuts or breaks in continuity with the PINK Wire leading to PIN "E"... THIS Diagram shows how the harness is routed over and around the upper areas of the 4L60E to the Passenger Side of the Transmission and where to "squeeze" and pull the 20 Pin Round Connector off of the flange there and then guide the Wire Harness back up and over far enough to actually be able to unwrap the loom(s) as needed to trace down any separations in the PINK Wire:

 

[mrrsm]

As for some possible places to look for the Wire Breaks…. These are Two Excerpts from the same Thread with two problems and likewise two different solutions for both of them:

http://forums.trailvoy.com/showthread.php?t=100022

Problem #1

Anyone who reads this thread ignore posts #4 & 5 by me because it was not the fix.

I got that idea from seeing what some other gm/chevy truck owners did. I ended up undoing the relay etc after finding the problem. The PCM was not at fault. I thought that the ignition output to the Trans might have been weak so that's why I tried that.

Solution #1

In the end the solution was the connector on the valve body of the Transmission.

It is difficult to access without removing the Trans mount & cross member to lower it a little, to access the plug which is on the right side (passenger) top edge of the Trans, next to the frame rail. I managed to jam my hand up in there enough to unplug it without dropping the cross member.

If you have big hands/mitts don't even try, drop the frame, support it with a jack or stand and give yourself more access. Also I think the harness was either taped to another or clipped in, undo this and pull down gently to give yourself more length/access. The repair was permanent, I have not had anymore issues since I found the root cause.

Matttastic if you are still having that problem try unplugging the connector (Transmission) and cut the tape off and gently push pull (Wiggle Test) on the wires see if any feel broken or in my case fall out of the connector. Most likely it is one of the pink wires (can't remember pin position), which is the ignition feed to the Trans Solenoids from the PCM.

Problem #2

Thanks Dutch but my problem was on the other end electrically speaking. After dropping pan to check fluid condition and debris all checked out including solenoids. Changed ignition switch that dealer had changed two years prior even though battery voltage tested fine at fuse. Limp mode returned and I took to original dealer and I advised them I thought problem was electrical but not sure where.

After two days of road testing they said no problem existed and I should pick up. I refused and then they took for another road test where limp mode turned on and they still had no idea why. I was told to replace PCM. Then I was told that didn't fix issue and I was referred to a trani specialist. Picked up car from dealer and entire trani was shot- couldn't even get out of first. After much finger pointing and debate I agreed to pay cost for gm trani with free labor to install. Get car back and drive it for a day and limp mode and same codes return.

Solution #2

They tow car and take a week to figure out it's the connector/wiring on the connection to ignition switch! It was apparently dropping voltage intermittently. They asked me to pay $400 for that too! Ended up getting them to cover it, but still a horrible experience and not sure I could have solved it either way.

​

 

[Vale]

Ok I finally think I found what might be it. I took down the the pan and unplugged all selonoids as i was removing the selonoind in the back of the transmission passengers side one the piece that you plug into just fell off and so im going to take a guess here and say that might be it. Oh forgot after I noticed that I also checked for 12v on all plugs that go to selonoids and all but 1 didn't have 12v it had 11.9 . Now before I change that one would that be the tcc selonoid and could rgat be the problem?

 

[mrrsm]

It would help if you could take a few snaps of what you are working on down there and post them back up here... with a focus on anything that you mentioned being cracked or broken. Also... Prior to taking your DC Voltage measurements on the various Solenoids... Did you do a Baseline Voltage Check on your Truck Battery, so you know what it has as static storage to compare against your readings? That would be an easy task to do and very necessary to know. If you intend on charging the Battery... undo BOTH The Positive and Negative cables so you have the Charger isolated from the entire vehicle if you measure Low Voltage and decide to freshen up the Charge.

After it comes up to a Nominal 12+ VDC Level... Remove the Charger and Re-install the Positive Cable first; then the Negative Cable with the Ignition Key confirmed as being in the OFF Position First. If something broke free from the Solenoid while you were trying to extract it... try to determine if it was merely the Plastic Retainer for the Transmission Wire Harness Solenoid Connector. This might also be something metallic that dislodged from the Round Harness Socket that pokes up and through the hole in the Valve Body where it mates up to the External Wire Harness Round cable Connector. These might be two completely unrelated events if you are still reading "0" Volts off of the PIN "E" situated inside that Round External Harness Plug.

Therefore you would still be looking for a Broken PINK Wire or something loose from it y starting at that point where the two Round Male and Female Connectors meet and then heading up and out through the external wire harness until you can locate the break in the PINK Wire. Use a Bright Flash Light even in Daylight and look very closely at everything as you check things over. If you accidentally fractured the Plastic Retaining Clip that holds the Wire harness plug into the electrical connector of the solenoid... if you cannot use a Thin White Nylon Zip Tie to secure them back together... You may have to replace the entire harmess and the attached PWM Solenoid as well. Remember that your Mission is to find the Break in the PINK Wire First because the PXXXX Trans Codes all flow from THAT problem. If you fix the Break... The Solenoids may well all pass testing after that. Also ... if you are testing the Solenoids for Voltage... you should also be trying to measure their RESISTANCE Readings to determine what they Ohm out at for normal levels as well.

 

[Vale]

This is the broken selonoid.

 

[Mooseman]

Is it possible that because of this broken solenoid it may have shorted out and blown the fuse again after you first checked it? That could explain why you don't have power at pin E. You could also pull the fuse and check for continuity between the solenoid connectors and the fuse terminal. Careful toy don't jam anything too big in the terminal.