Silverado 3500 2WD V8-6.6L DSL Turbo VIN 2 (2004)
Ignition Relay: Testing and Inspection
IGNITION RELAY DIAGNOSIS
CIRCUIT DESCRIPTION
The EDU/IGN 1 relay is normally an open relay. The relay armature is held in the open position by spring tension. When the ignition switch is turned
to the Run or Start position, current will flow through the relay coil. A wire connected to the other end of the relay coil completes the path to ground
through the engine control module (ECM). The electromagnetic field created by the relay coil overcomes the spring tension and moves the armature,
allowing the contacts to close. The closed relay contacts allow current to flow from the battery to the following fuses:
-
The ECM RPV fuse
-
The EDU fuse
When the ignition switch is turned to the OFF position, the electromagnetic field collapses. This action allows the spring tension to move the armature
away from the relay contacts, which interrupts current flow to the fuses.
If the EDU/IGN 1 relay fails to close, the engine will crank but will not run. The class 2 communications will be available with the use of a scan tool.
The EDU/IGN 1 relay table assumes that the vehicle battery is fully charged.
TEST
