Theory Of Operation

WARNING: This page is about a different car, the 2014 RAM 3500 HD and 2014 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The PCM/TCMl Relay is used to supply power (Transmission Control Output) to the Transmission Solenoid/TRS Assembly when in normal operating mode and to pins C4-19, C4-28 and C4-38 of the PCM. The purpose of the PCM/TCM Relay is to allow the Powertrain Control Module (PCM) to turn off the power to the Transmission Solenoid/TRS Assembly in event that the transmission should need to be placed into "limp-in" mode due to a DTC.

After a PCM reset, (ignition switch turned to the run position, or after cranking engine) the PCM verifies that the PCM/TCM Relay contacts are open by checking for voltage on the Transmission Control Output circuit before the PCM/TCM Relay is energized. If voltage is detected, the DTC will set.

NOTE:

Due to different power control configurations, the Transmission Control Relay may be referred to as a PCM relay.