Chevrolet Silverado / GMC Sierra. Service manual — part 2791

of electromagnetic interference that may result from installation of aftermarket equipment

Reference Information

Schematic Reference

Trailer Brake Control Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Trailer Brake Controls 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

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TBCM replacement, setup, and programming

DTC C056D OR C056E

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

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

DTC C056D 33

ECU Hardware Performance Special Memory Failure

DTC C056D 34

ECU Hardware Performance RAM Failure

DTC C056D 35

ECU Hardware Performance ROM Failure

DTC C056D 36

ECU Hardware Performance EEPROM Failure

DTC C056D 39

ECU Hardware Performance Internal Electronic Failure (ECU processor failure)

DTC C056E 41

ECU Software Performance Operational Software/Calibration Set Not Programmed

Circuit/System Description

This diagnostic applies to internal microprocessor integrity conditions within the Trailer Brake
Control Module (TBCM). This diagnostic also addresses if the TBCM is not programmed.

Conditions for Running the DTC

C056D

The Ignition is ON, and DTC C056D runs once an ignition cycle.

C056E

The ignition is ON, with the engine OFF, DTC C056D runs continuously.

Conditions for Setting the DTC

C056D

The TBCM detected a failure in its microprocessor.

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

C056E

The TBCM is not programmed.

Action Taken When the DTC Sets

The trailer brake control will be disabled at the end of the current brake apply for the
remainder of the ignition cycle.

The Service Trailer Brake System will be displayed on the Driver Information Center
(DIC).

Conditions for Clearing the MIL/DTC

When the condition for the DTC is no longer present.

The TBCM automatically clears the history DTC when a current DTC is not detected in 40
consecutive drive cycles.

Reference Information

Schematic Reference

Trailer Brake Control Schematics

Connector End View Reference

Component Connector End Views

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

Ignition ON, observe the DTC information with a scan tool. DTC C056D and DTC C056E,
should not set.

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado

If DTC C056D failed this ignition, replace the TBCM.

If DTC C056E failed this ignition, program the TBCM.

Circuit/System Testing

C056E

Program the TBCM. If DTC C056E sets after programming, perform the following steps:

If DTC C056D is set, turn off the ignition, wait 30 seconds, turn ignition on, if DTC C056D
failed this ignition cycle, replace the TBCM.

If DTC C056E is set, turn off the ignition, wait 30 seconds, turn ignition on, if DTC C056E
failed this ignition cycle, program the TBCM.

If DTC C056E sets after programming, replace the TBCM.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TBCM replacement, setup, and programming

DTC C0800

Diagnostic Instructions

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

Strategy Based Diagnosis for an overview of the diagnostic approach.

Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptor

DTC C800 03

Device Power Circuit Voltage Below Threshold

DTC C800 07

Device Power Circuit Voltage Above Threshold

Circuit/System Description

2008 Chevrolet Silverado 1500

2008 BRAKES Trailer Brake Controls - Cab & Chassis Sierra, Cab & Chassis Silverado, Sierra & Silverado