Cannot communicate with ECU (Powertrain control module)?

Tiny
LCC_PAUL
  • MEMBER
  • 2012 RAM 3500
  • 6.7L
  • 6 CYL
  • TURBO
  • 4WD
  • AUTOMATIC
  • 175,000 MILES
When scanning the vehicle with an Autel scan tool, I am able to communicate with all vehicle computers except the PCM. I have checked all circuits and everything checks out, except the following:

1. Ignition does not recognize that there is a key in it, even though one is in, and is turned to start position for data acquisition. I have had a couple instances where the key is identified in the ignition, but doesn't change the communications. Also, the message screen does not seem to care what key is used, as I have experimented with other similar vehicle keys and do not get the "wrong key" error message. While in the Central Gateway 'Live Data' screen, it shows no key in ignition, as well as the sentry key was not active, or not present.

2. While testing circuits I found that the
OFF/RUN/
START
CONTROL
OUTPUT
Circuit was incorrect according to the manual's schematics. The manual shows a pk/wt wire leaving the TIPM via pin 49 in the C1 block, goes through pin 7 in the C130 connector, then ending at the PCM C2 plug pin 29. When continuity testing this wire goes to pin 69 on the PCM C2 plug.

3: While continuity testing the TIPM circuit from pin 26 in block C2, it correctly runs to pin 1 in the PCM C2 plug but also feeds signal to the pin 29 mentioned in the above #2 condition.

How can I get comms established with the PCM?

Can you provide pinout images for the PCM C2 plug and the C130 connector please?
Monday, January 27th, 2025 AT 3:28 PM

9 Replies

Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,500 POSTS
If you have power and grounds for the PCM it should communicate. Have you checked them with the system on? Also, you could have a shorted sensor that is shutting the PCM down. What does the C130 connector go to so I can look it up. Here is the PCM C2 plug pin out as requested. Check out the images (below). Please let us know what happens.
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Tuesday, January 28th, 2025 AT 9:56 AM
Tiny
LCC_PAUL
  • MEMBER
  • 11 POSTS
The C130 connector attaches the TIPM harness to the PCM. It is attached to the bottom of the cowl almost right in front of the driver.
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Tuesday, January 28th, 2025 AT 11:38 AM
Tiny
KEN L
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The highest number for the TIPM is C8? And the PCM is C6.
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Wednesday, January 29th, 2025 AT 8:31 AM
Tiny
LCC_PAUL
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  • 11 POSTS
Yes, the group of harnesses leaves the TIPM to various connectors. Wires from blocks C1, C2, C5 end up going to the PCM C2 plug via the C130 connector. It joins the engine harness along the front edge of the cowl in the engine compartment to the harnesses coming out of the TIPM.

Also, how does one go about testing/resetting the key sentry so that we can eliminate that the PCM has not been immobilized by it?
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Wednesday, January 29th, 2025 AT 10:16 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,500 POSTS
Yes! Found it, here you go the c130 connector pin outs. Check out the images (below). Let us know what you find.
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Thursday, January 30th, 2025 AT 11:50 AM
Tiny
LCC_PAUL
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Great, thank you. All of that checks out. I'm now thinking the key sentry immobilized the PCM due to the harness and TIPM change. How does one reset that?
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Friday, January 31st, 2025 AT 8:43 AM
Tiny
KEN L
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I don't think that will hinder the PCM communication.
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Friday, January 31st, 2025 AT 10:09 AM
Tiny
LCC_PAUL
  • MEMBER
  • 11 POSTS
Okay, we are using an Autel scanner, it will identify the VIN and vehicle, as well as allow all functions to all of the vehicle systems and computers except the PCM. It says it cannot communicate with PCM.
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Thursday, February 6th, 2025 AT 6:07 AM
Tiny
KEN L
  • MASTER CERTIFIED MECHANIC
  • 51,500 POSTS
I would disconnect the ignition coils, oxygen sensors and fuel injector wiring. If one of these are shorted, it will shut down the PCM. If the PCM is getting power and grounds and the disconnection does not make a difference I would send the PCM in for testing. Here is how in the images below.
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Thursday, February 6th, 2025 AT 9:10 AM

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