Ems Main Relay

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

When the ignition is turned on, battery voltage is applied to the ignition sense input. The ECM then starts its power up routines and energizes the EMS main relay.

When the ignition is turned off, the 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 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 ECM de-energizes the EMS main relay.