NOTE: Diagnostic trouble code tests are written specifically for use with GM Tech I or Tech II scan tools. Generic scan tool can be used but may have limited functions. This article only covers the portion of those systems which relates to cruise control system diagnosis. For further information, see appropriate Diagnostic System Check for the system in which customer concern is addressed.

Body Control Module (BCM) is equipped with a self-diagnostic system which detects system abnormalities. When a malfunction occurs, BCM will store a DTC. See BODY CONTROL MODULE (BCM) DTC DEFINITIONS . Malfunctions are recorded as history/intermittent failures or as current failures. Current DTCs indicate BCM has detected a fault which is currently present. A history DTC indicates that BCM has previously detected a malfunction that is not currently present.

The BCM Diagnostic System Check is the starting point for identifying which module(s) on the class 2 device is responsible for issuing the DTC. The Diagnostic System Check will direct the technician to the correct diagnostic procedure for the identified module.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

Self-Diagnostic System: Notes

Use the Manual With the Right Hardware

When to See a Mechanic

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