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Home >> Jaguar >> 2011 >> XF Base >> Repair and Diagnosis >> Engine Performance >> Engine Control Systems >> Electronic Engine Controls (V8 N/A 5.0L Petrol) >> Electronic Engine Controls (V8 5.0L Petrol) >> Description And Operation >> System Operation And Component Description >> Component Descriptions >> Main Relay
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Main Relay

The main relay is used to initiate the power up and power down routines within the engine control module (ECM). The main 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 main relay.

When the ignition is turned off, the engine control module (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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