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sprinkles08, ASE Certified Technician
Category: Transmissions
Satisfied Customers: 22698
Experience:  Chrysler/Dodge/Jeep master tech ASE Master and Advanced Certified, Chrysler/Dodge/Jeep Master Certified, Trans Specialist
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I have a 2008 Chevy Express 3500 with the 4L80E

Customer Question

I have a 2008 Chevy Express 3500 with the 4L80E transmission. Trouble codes (p0700 & p0976) came up. I cleared codes for a test drive. Run through all gears auto/manually fine. Downshift through all gears to first (engine break style) and DTCs kick back on. First gear engages and disengaged (not slipping) into 3rd (I believe, because second gear does the same engage/disengage jerk). After DTCs kick on the limp mode won't allow down shifting to first. Shifting is hard/jerky on the lower gears also.
Submitted: 1 year ago.
Category: Transmissions
Expert:  sprinkles08 replied 1 year ago.
Hello and welcome to JustAnswer!
P0976 is for the 2-3 shift solenoid circuit. This code sets when there is low voltage seen on the solenoid control circuit. The solenoid receives power from the trans fuse along with all the other solenoids and the trans controller duty cycles ground to control the solenoid. The code could be setting because of an open circuit between the TCM and solenoid, a short to ground on the control wire, or an open solenoid. A loss of power from the fuse could also cause it but then you should have codes setting for all solenoids.
Odds are the solenoid is the issue. A visual inspection of the wiring and connections can be done, if nothing is seen then it would take some electrical testing at the time the problem is happening to know exactly what is going on and rule out or condemn wiring. Nearly all solenoid codes are set by incorrect solenoid winding resistance.
Customer: replied 1 year ago.
That does not answer my question at all. You are not the Chevy tech that I thought I was emailing. why? I'm looking for a master mechanic familiar with the 4L80E. I am a small fleet mechanic keeping seven vehicles (E350s & express 3500s) operational on the Big Island of Hawai'i. I have been wrenching for over 20 years myself and I'm not looking for quess work.The 1 2 2 3 shift solenoids are good... There is power down at the down at the transmission connection. My next step is checking continuity to ground by disconnecting at the computer and transmission harness (LG & YB wires). The trans side of the harness had wires fusing together slightly. What I mean by this several wires had to be pulled apart from each other but no wires melted through. There is some slight trans fluid in the PIN area of the pass through connector. Could the codes coming up be connected to another part of the circuit that I'm missing, such as the 4l80e internal harness? Can I test that? If all is well and I need to back track up towards the cpu and/or this is something I just cannot complete a scanner the has component activation capabilities... Well, I got a little frustrated and decided to yield to my better judgement and ask/pay for help. Are you the guy who can do that?Jimbo
Expert:  sprinkles08 replied 1 year ago.
The 2-3 solenoid is a yellow/black wire. If the solenoid has been verified good, which would be done by checking it's resistance through the trans connector while the code is active which also tests the internal wiring, then that leaves only the wire from the trans to the TCM. It could have an open circuit or it may be shorted to ground, it will either need to be tested at the time the problem is happening or hard wired.
Customer: replied 1 year ago.
Are you serious? You just repeated what I just said. Are you a Chevy master technician? I am unsatisfied with your service... Where do we go from here?
Expert:  sprinkles08 replied 1 year ago.
I verified what the correct next step in diagnosing the problem is, a control circuit issue is one of the possible causes I described in my first post. If the solenoid and internal trans harness have been tested while the problem is happening then the next step will be to test or replace the wire from the trans to the TCM.