Main relay (system relay)
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The function of the main relay (system relay) is to supply certain components with voltage.
The relay is mechanical and has a closing/opening function. In the rest position the circuit in the relay is open.
The main relay terminals (#30 and #86) are supplied with voltage by the battery. When the ignition key has been turned and the engine control module (ECM) is powered, the terminal (#85) on the main relay is grounded by the engine control module (ECM).
When the terminal (#85) is grounded, the relay is activated and a number of components are powered via the relay terminal (#87).
The engine control module (ECM) has diagnostics for the main relay.
The main relay is in the relay/fuse box in the engine compartment.