Theory Of Operation

WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The Transmission Control Relay is used to supply power to the solenoids and pressure switches (Transmission Solenoid/TRS Assembly) when the transmission is in normal operating mode. When the relay is off, no power is supplied and the transmission is in "limp-in" mode. The relay output is fed back to the PCM through pins C4-19, C4-28 and C4-38 and are referred to as "Transmission Control Relay Output".

Immediately after a controller reset (ignition key turned to the RUN position or after cranking engine), the TCM verifies the relay contacts are open by checking for no voltage at the transmission control relay output terminals. After this is verified, the voltage at the pressure switches are checked. There should be no voltage on the pressure switches at this time. The Powertrain Control Module (PCM) will activate the relay.