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Home >> Jaguar >> 2012 >> XKR 2D Coupe >> Repair and Diagnosis >> External Pages >> Different car >> Section 91 (Electronic Engine Controls - V8 N/A 5.0L Petrol -- XK/X150) >> Electronic Engine Controls - V8 N/A 5.0L Petrol >> Electronic Engine Controls >> Description And Operation >> Main Relay

Main Relay

WARNING: This page is about a different car, the 2015 Jaguar XK, 2014 Jaguar XK, 2013 Jaguar XK, and 2012 Jaguar XK. However, it is still accessible from the selected car via links, so may be relevant.

The main relay is used to initiate the power up and power down routines within the ECM. The main relay is installed in the PDB (power distribution 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 main relay.

When the ignition is turned off, the ECM maintains its powered up state while it conducts the power down routines (up to 20 minutes in extreme cases, when cooling fans are required) and on completion will turn off the main relay.

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