Chevrolet Silverado / GMC Sierra. Service manual — part 1311

The cruise control system becomes inoperative.

The ECM stores the DTC to memory.

The ECM will record the operating conditions at the time the diagnostic failed. The ECM
stores this information in Failure Records.

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.

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

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

2008 Chevrolet Silverado 1500

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

Control Module References for scan tool information

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector of the stop lamp switch.

2. Ignition ON, verify that a test lamp illuminates between the stop lamp switch voltage circuit

terminal B and ground.

If the test lamp does not illuminate, test the stop lamp switch voltage circuit for a short
to ground or an open/high resistance. If the circuit tests normal, test or replace the
RUN/CRANK Relay.

3. Ignition OFF, disconnect the harness connectors of the BCM X5, ECM X1, TCM (if

equipped), Power Take Off (PTO) module (if equipped) and Trailer Brake controller (if
equipped).

4. Ignition OFF, verify that a test lamp does not illuminate between the stop lamp switch

harness terminal A and B+.

If the test lamp illuminates, test the brake switch signal circuit for a short to ground.

5. Test for less than 1.0 ohm resistance between the stop lamp switch harness terminal A and

one of the following:

ECM connector X1 terminal 83 for the 6.6L engine.

ECM connector X1 terminal 55 for the 4.3L engine.

ECM connector X1 terminal 9 for the 4.8L, 5.3L, 6.0L, 6.2L or 7.0L engines.

If resistance is not as specified, test the stop lamp switch circuit for an open/high
resistance.

6. Ignition ON, verify that a test lamp does not illuminate between the stop lamp switch TCC

brake signal circuit terminal A and ground.

If the test lamp illuminates, test the brake switch signal circuit for a short to voltage.

7. If all circuits test normal, test or replace the stop lamp switch. If the component and all

circuit tests are normal, replace the ECM.

Component Testing

Relay Test

1. Ignition OFF, disconnect the RUN/CRANK relay.

2. Test for 60-180 ohms of resistance between terminals 85 and 86.

If the resistance is not within the specified range, replace the relay.

3. Test for infinite resistance between the following terminals:

2008 Chevrolet Silverado 1500

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

30 and 86

30 and 87

30 and 85

85 and 87

If less than infinite resistance, replace the RUN/CRANK relay.

4. Install a 20-amp fused jumper wire between relay terminal 85 and 12 volts. Install a jumper

wire between relay terminal 86 and ground. Test for less than 2.0 ohms of resistance
between terminals 30 and 87.

If greater than 2.0 ohms, replace the RUN/CRANK relay.

Switch Test

1. Ignition OFF, disconnect the stop lamp switch.

2. With the brake pedal released, measure for infinite resistance between terminals A and B of

the switch.

If resistance is measured, replace the switch.

3. With the brake pedal released, measure for less than 1.0 ohm resistance between terminals C

and D of the switch.

If resistance is not as specified, replace the switch.

4. With the brake pedal applied, measure for less than 1.0 ohm resistance between terminals A

and B of the switch.

If resistance is not as specified, replace the switch.

5. With the brake pedal applied, measure for infinite resistance between terminals C and D of

the switch.

If resistance is measured, replace the switch.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Stop Lamp Switch Replacement (Non-Adjustable Pedal) or Stop Lamp Switch
Replacement (Adjustable Pedal)

Control Module References for ECM replacement, setup, and programming.

DTC P0572 OR P0573

Diagnostic Instructions

2008 Chevrolet Silverado 1500

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

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 P0572 00

Brake Switch Circuit 1 Low Voltage

DTC P0573 00

Brake Switch Circuit 1High Voltage

Diagnostic Fault Information

Circuit/System Description

The TCC Brake signal circuit is a high voltage input to the body control module (BCM), engine
control module (ECM), transmission control module (TCM), Power Take Off (PTO) module (if
equipped) and Trailer Brake controller (if equipped). The BCM monitors the stop lamp switch
circuit to detect when the brake pedal has been applied. The ECM monitors the TCC Brake
signal to determine when the brake pedal is applied. When the brake pedal is applied, the BCM
sends a serial data message to the ECM indicating that the brake pedal has been applied. The
ECM senses a high voltage signal on the brake switch signal circuit when the stop lamp switch is
closed.

Conditions for Running the DTC

The engine is running.

Battery voltage is greater than 11.5 volts.

Conditions for Setting the DTC

P0572 00

Circuit

Short to

Ground

Open or High

Resistance

Short to

Voltage

Signal

Performance

Ignition 1 Voltage

P0572 00

P0572 00

-

-

TCC Brake Signal

P0572 00

P0572 00

P0573 00

-

2008 Chevrolet Silverado 1500

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