Chevrolet Silverado / GMC Sierra. Service manual — part 2796

Circuit/System Description

The trailer brake relay control circuit high SSR enable circuit short to battery monitors for short-
to-high faults on the trailer brake solid state relay (SSR) enable circuit. In general, the SSR
enable short-to-high circuit diagnostic is executed whenever the SSR has been disabled for a
minimum duration. Typically, the diagnosis is executed at TBCM power up. The diagnosis test
passes, if TBCM detected the status is correct for consecutive 16 samples.

Conditions for Running the DTC

The ignition is ON.

This DTC runs once per ignition cycle within the enabling conditions.

Conditions for Setting the DTC

The TBCM detects short to battery positive in the solid state relay control 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.

If DTC C1114 is set as a current DTC, diagnose first before diagnosing DTC C1113. 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.

Reference Information

Voltage Circuit

2008 Chevrolet Silverado 1500

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

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 Trailer Brake Relay Status parameter.

The reading should be Enabled or Disabled.

2. Ignition ON, observe the scan tool brake controls TBCM Command Duty Cycle parameter.

The reading should be 0 - 100 percent.

Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the solid state relay module.

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

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

3. Ignition ON, test for 9 - 11 volts between the 10-volt relay control circuit terminal E and

ground.

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 less than the specified range, test the 10-volt relay control 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 10-volt relay control circuit for a short to
voltage. If the circuit tests normal, replace the TBCM.

4. Ignition OFF, reconnect the harness connector at the solid state relay module.

5. Connect a test lamp between the control circuit terminal C of the trailer connector and the

ground circuit terminal B.

6. Command the trailer brake relay ON and OFF with a scan tool. The test lamp should turn

ON and OFF when changing between the commanded states.

If the test lamp is always ON, test the control circuit for a short to voltage. If the
circuit tests normal, replace the TBCM.

If the test lamp is always OFF, test the control circuit for a short to ground or an
open/high resistance. If the circuit tests normal, replace the TBCM.

7. If all circuits test normal, test or replace the trailer brake solid state relay (SSR).

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Trailer Brake Control Module Replacement

Control Module References for TBCM replacement, setup, and programming

DTC C1114

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 C1114

Trailer Brake Control Solenoids Control Circuit-Trailer Auxiliary Supply Voltage

Diagnostic Fault Information

Short to

High

Short to

Signal

2008 Chevrolet Silverado 1500

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

Circuit/System Description

The trailer brake control module (TBCM) monitors for faults on the trailer brake solid state relay
(SSR) output auxiliary supply voltage circuit for fault for a short to ground, short to battery, or
open circuit.

Conditions for Running the DTC

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

The 5 volt supply for the SSR output auxiliary supply circuit is not faulted and DTC C0870
is not set as current DTC.

The SSR relay control circuit fault DTC C1112 is not set as current DTC.

Conditions for Setting the DTC

DTC C1114 will set as current DTC, if one of the following conditions is true:

The TBCM detects an open in the trailer auxiliary supply voltage circuit.

The TBCM detects short to ground in the trailer auxiliary supply voltage circuit.

The TBCM detects short to battery positive in the 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

Circuit

Ground Resistance

Open

Voltage Performance

Trailer Auxiliary Supply
Voltage Circuit

C1114

C1114

C1114

-

SSR Relay Control Circuit

C1114

-

-

-

-

SSR Ground Circuit

-

-

C1114

-

-

2008 Chevrolet Silverado 1500

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