ECM Relay

The engine control module (ECM) relay is used to initiate the power up and power down routines within the engine control module (ECM). The engine control module (ECM) relay is installed in the engine junction box (EJB).

When the ignition is turned on, battery voltage is applied to the ignition sense input. The engine control module (ECM) then starts its power up routines and energizes the engine control module (ECM) relay.

When the ignition is turned off, the engine control module (ECM) 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 DMTL system is running (NAS markets) or the transmission control module (TCM) is 'kept awake' because of a 'not in park' condition
• Up to 5 minutes when cooling fans are required.

On completion of the power down routines the engine control module (ECM) de-energizes the engine control module (ECM) relay.