Starting System - Ignition Relay Diagnosis Update

File In Section: 06 Engine/Propulsion System

Bulletin No.: 03-06-04-026

Date: April, 2003

SERVICE MANUAL UPDATE

Subject:
Revised Ignition Relay Diagnosis

Models:
2003 Chevrolet Silverado
2003 GMC Sierra
with 6.6L Engine (VIN 1 - RPO LB7)

This bulletin is being issued to revise the Ignition Relay Diagnosis in the Engine Controls sub-section of the Service Manual. Please replace the current information in the Service Manual with the following information.

The following information has been updated within SI. If you are using a paper version of this Service Manual, please make a reference to this bulletin on the affected page.

Circuit Description

The ignition 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 ignition 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 ignition relay table assumes that the vehicle battery is fully charged. Refer to Battery Inspection/Test in Engine Electrical.





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