Chevrolet Silverado / GMC Sierra. Service manual — part 2799

If greater than the specified range, test the 5-volt reference circuit for a short to
voltage. If the circuit tests normal, replace the TBCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 4 and the 5-volt reference

circuit terminal 3. Verify the scan tool Manual Apply Switch is greater than 90 percent.

If less than the specified range, test the signal circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the TBCM.

5. If all circuits test normal, test or replace the trailer brake controller switch panel.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TBCM replacement, setup, and programming

Trailer Brake Control Module Replacement

DTC C1117

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 C1117

Manual Trailer Brake Apply Request circuit Signal 2-Redundant Manual Apply Signal

Diagnostic Fault Information

Circuit/System Description

Circuit

Short to

Ground

High

Resistance

Open

Short to

Voltage

Signal

Performance

TBCM 5-Volt Reference
Circuit

C1117

-

C1117

C1117

-

Redundant Manual Apply
Signal Circuit

-

-

C1117

-

-

TBCM Ground Circuit

-

-

C1117

-

-

2008 Chevrolet Silverado 1500

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

The redundant manual apply switch circuit diagnostic monitors for circuit faults on the redundant
manual apply switch input to the trailer brake control module (TBCM).

This DTC will also be detected when a fault is detected in the 5 v reference voltage or in TBCM
ground circuit

Conditions for Running the DTC

The system voltage is in the range of 9.5 - 17 volts.

The module is powered up and completes initialization.

Conditions for Setting the DTC

DTC C1117 will set as current DTC, if one of the following conditions is true:

The TBCM detects an open in the redundant manual apply signal circuit.

The TBCM detects short to ground in the redundant manual apply signal circuit.

The TBCM detects short to battery positive in the redundant manual apply signal circuit.

Action Taken When the DTC Sets

The trailer brake control will be disabled for the remainder of the ignition cycle.

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

Condition 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.

Diagnostic Aids

If there are any DTCs set for GMLAN communication such as U0100, U0121, U0140, or U2099,
diagnose them first before to resolve DTCs described in this section.

When the manual apply switch 5-volt reference circuit or TBCM ground is open circuit, in
addition to setting DTC C1116, DTC C1117 and C1118 may also be set as current DTC. In this
case, diagnose the apply switch 5-volt reference circuit or TBCM ground first for open circuit
fault before to diagnosing DTC C1117. If there is an aftermarket trailer brake controller, the
ITBC must be disconnected. Do not power both ITBC and aftermarket controllers to control the
trailer brakes at the same time.

2008 Chevrolet Silverado 1500

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

Reference Information

Schematic Reference

Trailer Brake Control Schematics

Description and Operation

Trailer Brake Controls Description and Operation

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

1. Ignition ON, observe the scan tool brake controls Primary Manual Apply parameter. The

reading should be between 0-100 percent and change with brake pedal input.

2. Ignition ON, observe the scan tool brake controls Redundant Manual Apply parameter. The

reading should be between 0-100 percent and change with brake pedal input.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the trailer brake controller switch panel.

2. Test for less than 5 ohms of resistance between the ground circuit terminal 8 and ground.

If greater than the specified range, test the ground circuit for an open/high resistance.

IMPORTANT: All electrical components and accessories must be turned OFF

and allowed to power down.

2008 Chevrolet Silverado 1500

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

If the circuit tests normal, replace the TBCM.

3. Ignition ON, test for 4.8 - 5.2 volts between the 5-volt reference circuit terminal 3 and

ground.

If less than the specified range, test the 5-volt reference circuit for a short to ground or
an open/high resistance. If the circuit tests normal, replace the TBCM.

If greater than the specified range, test the 5-volt reference circuit for a short to
voltage. If the circuit tests normal, replace the TBCM.

4. Install a 3A fused jumper wire between the signal circuit terminal 5 and the 5-volt reference

circuit terminal 3. Verify the scan tool Redundant Manual Apply Switch is greater than 90
percent.

If less than the specified range, test the signal circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the TBCM.

5. If all circuits test normal, test or replace the trailer brake controller switch panel.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for TBCM replacement, setup, and programming

Trailer Brake Control Module Replacement

DTC C1118

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 C1118

Trailer Brake Control Sensitivity Switch Circuit

DTC C1118 08

Trailer Brake Control Sensitivity Switch Circuit Signal Invalid

Diagnostic Fault Information

2008 Chevrolet Silverado 1500

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