P1D20 JEEP – Multi Module Handshake Failure

P1D20 JEEP Possible Symptoms

Engine Light ON (or Service Engine Soon Warning Light)

P1D20 JEEP Possible Causes

Faulty Electronic Shifter Module (ESM) Internal Error,Faulty Transmission Control Module (TCM) Internal Error

P1D20 JEEP Description

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.