P1D20

P1D20-MULTI MODULE HANDSHAKE FAILURE

For a complete wiring diagram Refer to the Wiring Information.

Theory of Operation

The purpose of the diagnostic is to monitor the question-answer CAN communication between the Electronic Shifter Module (ESM) and the Transmission Control Module (TCM) by comparing the ESM response to the expected value within the TCM software. The TCM sends two randomly generated values to the ESM and the ESM is expected to answer with a value calculated based upon these two random numbers. The TCM commands the ESM to reset if one of the following conditions occurs: No answer received within a calibrated amount of time, received answer is incorrect and is the same as the previous answer or the received answer is incorrect and is not the same as the previous answer.

- When Monitored:
When the ignition switch is in the run position.

- Set Condition:
A failure is detected if the number of commanded ESM resets are greater than a calibrated threshold. The fault that's stored corresponds to the reason of the last commanded reset.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. 8HP45 Pre-Diagnostic Troubleshooting Procedure
VERIFY DTC IS ACTIVE

NOTE: For vehicle communication problems, use the scan tool to refer to the Network Review Screen. The screen depicts a high level view of the vehicle network. Fault and problem areas appear in red. Selecting any of the network components allows access to the source of the problem.

1. Turn the ignition ON.
2. With the scan tool, read active DTCs.

Is DTC U0101 and/or U11C3 active?

Yes

- Perform the U0002-CAN C BUS Off Performance diagnostic procedure. U0002

No

- Perform the Stored Lost Communication DTCs diagnostic procedure. Stored Lost Communication DTCs