#1- TCM not communicating or responding?

PETEY321

MEMBER
2008 DODGE CARAVAN
3.8L
6 CYL
2WD
AUTOMATIC
141,000 MILES

I'm working with an X7 bi-directional scanner that has its latest update. I'm pulling several codes under an automatic scan, but the TCM (2nd module in scan) doesn't pass or pull a code it just moves on without an entry. When selecting a TCM test only, it comes back with "received an invalid response" also won't perform any of the testing or special functions the scanner supports for drivetrain. I need a wiring diagram for the. PCM I guess. I've learned this year's model doesn't have a separate TCM, but instead, is integrated inside the PCM. One piece of hardware for both modules. Other than testing fuses and relays, and manually cracking open the wiring harness and visually inspecting wiring (without being able to identify any) checking for breaks, pinches, cuts, and corrosion etc, I'm not sure how to proceed troubleshooting.

8 Replies

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

I would remove the PCM connectors to check for corrosion, the placement of the PCM allows a lot of moisture. Also, this car has a TIPM which has issues, I have also found the engine and transmission wiring diagrams so you can check for power and grounds to the PCM, this guide will help.

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

I also have included how to replace the TIPM which is easy because it-self learns. Check out the diagrams (below). Please let us know what happens.

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Thursday, August 18th, 2022 AT 6:05 PM

PETEY321

MEMBER
23 POSTS

Thanks Ken,

I have already inspected the PCM and TIPM connections and pulled apart the associated wiring harnesses and looked at each wire individually (very time consuming). I didn’t find anything obvious but some of them had insulation that has become hard and brittle albeit intact and unbroken (on the outside anyway). I was working on the wiring after my initial question and have this to add...
While testing the wiring of TIPM, (fuses, relays, and current draw), I found these symptoms:

1. Slight drop when disconnecting large fuse #J7-(30A) ABS VALVE/ESP. Drop of.3 amps.

2. J13- (40A) EBL. Drop of1.25 amps.
3. Fuse M28- (10A) NGC/TRANS FEED (BATT)
when pulled, amperage went from a steady 5.15 to unstable fluctuations b/w 3.5 and 6.3 amps with spikes up to 10.2. Radiator electric fan attempts to come on but just surges without operating and relays K1 & K2 both click incessantly. There’s another relay in the harness between the upper radiator hose and left headlight that if removed, then pulling fuse 28 activates the radiator fan and stops when fuse is reconnected.

I’ll report back after incorporating wiring diagrams onto the process.

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Thursday, August 18th, 2022 AT 7:59 PM

PETEY321

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23 POSTS

I was looking over your diagrams and I believe they are for a 4 speed. Mine is a 62TE (6 speed). Will these diagrams work?

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Thursday, August 18th, 2022 AT 8:33 PM

KEN L

MASTER CERTIFIED MECHANIC
48,363 POSTS

Here are the 6 speed transmission wiring diagrams below. Let me know what you find.

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Friday, August 19th, 2022 AT 11:29 AM

PETEY321

MEMBER
23 POSTS

Ken,

Can’t report any real progress in the wiring area. I have found that I have an integrated PCM/TCM module. I’m unable to communicate or manipulate any of its functions and don’t get much information while running full scans. I am getting some information out of gear clutches and solenoid pressures. There are pressure problems, and I can’t actuate any of the solenoids or gear clutches. I checked for continuity of pin-to-pin wiring from the transaxle main harness connector to PCM connector and none are broken. I know I have a leak coming out if the bottom where transmission joins engine. It drips from a cover plate that is held in with 4-6 bolts.
I’m going to try and isolate the leak and back off the electrical for a moment. Do you have a diagram of the PCM connections/wiring that can assist in testing all powers and grounds associated with PCM? I’m also getting lost communication with PCM codes in other places.