Chevrolet Silverado / GMC Sierra. Manual — part 1313

1. Verify that B3794 is not set as current.

If B3794 is set as current, refer to DTC B3794.

2. Road test the vehicle and attempt to engage cruise. Verify that cruise control engages

properly and that DTC P0575 is not set.

If the cruise control system does not operate properly and DTC P0575 is not set, refer
to Cruise Control Malfunction.

If DTC P0575 sets as current, replace the BCM. Clear the DTC and road test the vehicle
and attempt to engage cruise. If DTC P0575 resets as current, replace the ECM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM or ECM replacement, setup, and programming

DTC P0703

Diagnostic Instructions

Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

Review Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor

DTC P0703

Brake Switch Circuit

IMPORTANT:

This DTC may be stored as a history DTC without affecting
the operation of the BCM. If stored only as a history DTC and
not retrieved as a current DTC, do not replace the BCM or
ECM.

Using the Failure Records data may help locate an
intermittent condition. If you cannot duplicate the DTC, the
information in the Failure Records can help determine how
many miles since the DTC set. The Fail Counter and Pass
Counter can help determine how many ignition cycles that
the diagnostic test reported a pass and/or a fail.

2008 Chevrolet Silverado 1500

2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Circuit/System Description

The body control module (BCM) monitors the stop lamp switch, mounted on the brake pedal.
The BCM sends a GMLAN serial data message to the engine control module (ECM) indicating
the status of the stop lamp switch.

Conditions for Running the DTC

The engine is ON.

Conditions for Setting the DTC

The ECM receives an invalid brake pedal status GMLAN serial data message from the
BCM.

This diagnostic runs continuously.

Action Taken When the DTC Sets

The Cruise Control System is disabled.

The ECM stores the DTC information into memory when this diagnostic runs and fails.

The malfunction indicator lamp (MIL) will not illuminate.

All of the scan tool cruise control function switch parameters are set to Off.

Conditions for Clearing the DTC

A last test failed, or the current DTC, clears when the diagnostic runs and does not fail.

A history DTC clears after 40 consecutive warm-up cycles, if failures are not reported by
this or any other emission related diagnostic.

Use the scan tool in order to clear the DTC.

Diagnostic Aids

Ensure all the stop lamps operate properly. Refer to Exterior Lighting Systems Description
and Operation to avoid misdiagnosis. If the vehicle stop lamps operate improperly, refer to
Symptoms - Lighting .

Reference Information

Schematic Reference

Cruise Control Schematics

Exterior Lights Schematics

2008 Chevrolet Silverado 1500

2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

Testing for Intermittent Conditions and Poor Connections

Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

1. Verify proper operation of the vehicle stop lamps. refer to Exterior Lighting Systems

Description and Operation .

If the vehicle stop lamps do not operate as described, refer to Symptoms - Lighting .

2. Ignition ON, press and release the brake pedal several times. With a scan tool, verify DTC

P0703 is not set as current in the ECM.

If DTC P0703 is current in the ECM, replace the BCM.

3. The system is OK. Clear the history DTC. Do not replace any components.

Repair Procedures

IMPORTANT: Repair any Brake System related DTCs before using this

diagnostic.

IMPORTANT: This DTC may be stored as a history DTC without affecting the

operation of the BCM. Do not replace the BCM if this DTC is
stored only as a history DTC and is not retrieved as a current
DTC.

2008 Chevrolet Silverado 1500

2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for BCM replacement, setup, and programming

SYMPTOMS - CRUISE CONTROL

1. Before using the symptom diagnostic table, perform the Diagnostic System Check -

Vehicle , in order to verify the following conditions:

There are no DTCs set.

The module can communicate via the serial data link.

2. Review the system operation in order to understand the system functions. Refer to Cruise

Control Description and Operation.

Visual/Physical Inspection

Inspect for aftermarket devices which can affect the operation of the cruise control system.
Refer to Checking Aftermarket Accessories .

Inspect the accessible system components or the visible system components for obvious
damage or for obvious conditions which can cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to
Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the
symptom:

Cruise Control Malfunction

Cruise Control Indicator Malfunction (Switch Indicator Malfunction) or Cruise
Control Indicator Malfunction (IPC Indicator Malfunction)

CRUISE CONTROL INDICATOR MALFUNCTION (SWITCH INDICATOR MALFUNCTION)

Diagnostic Instructions

IMPORTANT: The following steps must be completed before using the symptom

tables.

2008 Chevrolet Silverado 1500

2008 ENGINE Cruise Control - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado