Powertrain Control Module Relay

WARNING: This page is about a different car, the 2019 Jaguar XE. However, it is still accessible from the selected car via links, so may be relevant.

The Powertrain Control Module (PCM) relay is used to initiate the power up and power down routines within the PCM.

The PCM relay is installed in the Engine Junction Box (EJB).

When the ignition is turned ON, startup battery voltage is applied to the ignition sense input from the Body Control Module/Gateway Module (BCM/GWM). The PCM then starts its power up routines and energizes the PCM relay.

When the ignition is turned OFF, the PCM maintains its powered up state while it conducts the power down routines.

This can be for:

Up to 20 minutes in extreme cases, when the Diagnostic Monitoring Tank Leakage (DMTL) system is running (North American Specification (NAS) markets).
Up to 5 minutes when cooling fans are required.

On completion of the power down routines the PCM de-energizes the PCM relay.