Chevrolet Silverado / GMC Sierra. Service manual — part 1314

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.

Diagnostic Fault Information

Circuit/System Description

The cruise control switch contains an LED that illuminates to indicate the cruise control system
has been switched ON. Voltage is applied through the ON/OFF switch to the LED when the
switch is pressed. The BCM provides the ground path for the LED through a dedicated dimming
control circuit. Pressing the switch again opens the switch and the lamp turns OFF.

Diagnostic Aids

This diagnostic assumes the cruise control system is operating properly and no DTCs are set. If
the cruise control system is malfunctioning, refer to Cruise Control Malfunction.

If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Reference Information

Schematic Reference

Cruise Control Schematics

Connector End View Reference

Component Connector End Views

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

Cruise Control Switch Supply
Voltage

1

1

1

-

-

Cruise Control Indicator
Dimming Control

3

2

2

2

-

1. Cruise Control Inoperative

2. Indicator Lamp Inoperative

3. Indicator Lamp Dimming Inoperative

2008 Chevrolet Silverado 1500

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

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 Verification

Engine ON, press and release the cruise control ON/OFF switch while observing the Cruise
On/Off Switch parameter in the ECM data list with a scan tool. The parameter should change and
the indicator lamp should turn ON or OFF accordingly each time the switch is actuated.

Circuit/System Testing

Disable the inflatable restraint steering wheel module when performing this diagnostic. Refer to
SIR Disabling and Enabling .

1. Ignition ON, with a scan tool observe the Cruise On/Off Switch parameter. Verify the

parameter changes each time the switch is actuated

If the parameter reads ON at all times replace the cruise control switch.

2. Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable

Restraint Steering Wheel Module Replacement .

3. Disconnect the harness connector at the cruise control switch assembly.

4. Ignition ON, test for 0 volts between the cruise control harness connector terminal 9 and

ground.

If voltage is present, test the circuit for a short to voltage.

5. Ignition OFF, disconnect the X3 connector at the BCM.

6. Test for less than 1.0 ohm between the cruise control harness connector terminal 9 and the

BCM connector X3 terminal 22.

If greater than the specified value, test the circuit for an open or high resistance.

CAUTION: Refer to SIR Caution .

2008 Chevrolet Silverado 1500

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

7. Test for infinite resistance between the cruise control harness connector terminal 9 and

ground.

If resistance is measured, test the circuit for a short to ground.

8. If all circuits test normal, test the component. If the circuits and component tests are normal,

replace the BCM.

Component Testing

Disable the inflatable restraint steering wheel module when performing this diagnostic. Refer to
SIR Disabling and Enabling .

1. Ignition OFF, remove the inflatable restraint steering wheel module. Refer to Inflatable

Restraint Steering Wheel Module Replacement .

2. Remove the steering wheel cruise control switch. Refer to Steering Wheel Control Switch

Assembly Replacement .

3. Turn the cruise control switch ON. Connect a DMM positive lead to terminal 1 and the

negative lead to terminal 9 of the cruise control switch and measure the resistance. Verify
the meter reading indicates continuity.

If the reading indicates an open circuit, replace the cruise control switch assembly.

4. Connect the DMM positive lead to terminal 9 and the negative lead to terminal 1 of the

cruise control switch and measure the resistance. Verify the meter reading indicates an open
circuit.

If the reading is not as specified, replace the cruise control switch assembly.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Steering Wheel Control Switch Assembly Replacement

Control Module References for BCM replacement, setup, and programming

CRUISE CONTROL INDICATOR MALFUNCTION (IPC INDICATOR MALFUNCTION)

CAUTION: Refer to SIR Caution .

IMPORTANT: The cruise control switch must be ON in order to properly test the

switch indicator.

2008 Chevrolet Silverado 1500

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

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.

Circuit/System Description

The instrument panel cluster (IPC) illuminates the cruise control engaged indicator based on
serial data messages received from the engine control module (ECM) or the powertrain control
module (PCM). The indicator is commanded ON when the cruise control system is controlling
vehicle speed, and turned OFF with the system disengaged.

Diagnostic Aids

This diagnostic assumes the cruise control system is functioning normally and there are no
DTCs set. If the cruise control system is malfunctioning, refer to Cruise Control
Malfunction.

If any DTCs are set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

Reference Information

Schematic Reference

Cruise Control Schematics

Instrument Cluster Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Cruise Control Description and Operation

Indicator/Warning Message Description and Operation

Electrical Information Reference

Circuit Testing

Connector Repairs

2008 Chevrolet Silverado 1500

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