Trailer Brake Control System Cadillac Escalade GMT900

Fastener Tightening Specifications

Scheme 1

DIAGNOSTIC CODE INDEX

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provide an overview of each diagnostic category.

Circuit/System Description

The brake switch is hard wired to the trailer brake control module (TBCM). The body control module (BCM) sends a brake switch status serial data message to the trailer brake control module. The trailer brake control module compares the states of the brake switch signal to the serial data message after a master cylinder brake pressure sensor threshold is exceeded. If the brake switch signal and the serial data message are not in agreement or if the serial data message is not valid, a DTC will set and the trailer brake control system will be disabled.

Conditions for Running the DTC

1. Battery voltage is 9.5-17 V.
2. The module initialization has taken place.
3. The master cylinder brake pressure exceeds threshold

Conditions for Setting the DTC

1. The brake switch serial data message is not valid.
2. The actual brake switch input to the trailer brake control module, and the serial data information for the brake switch do not match.

Action Taken When the DTC Sets

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center will display Service Trailer Brake System.

Conditions for Clearing the DTC

1. The condition for the DTC is no longer present.
2. The TBCM 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

Description and Operation

Trailer Brake Controls Description and Operation

Electrical Information Reference

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, press the brake pedal. The brake lights should illuminate and the Brake Switch Status parameter should indicate ON.

Circuit/System Testing

1. Verify that DTC B3445, C0277, C0297, or C0890 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Ignition OFF, disconnect the harness connector of the trailer brake control module.
3. Ignition ON, test for greater than 11 V between the IGN 1 voltage circuit terminal 15 and ground. If less than the specified voltage, test the IGN 1 voltage circuit for a short to ground or an open/high resistance. If the circuit test normal and the MISC - IGN fuse is open, test the signal circuit terminal 37 for a short to ground. If the circuit tests normal, test or replace the RUN/CRANK relay.
4. If all the circuits test normal, replace the trailer brake control module.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) or «Relay Replacement (Within an Electrical Center)»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for TBCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The brake switch is hard wired to the fuel pump/trailer brake control module. The body control module (BCM) sends a brake switch status serial data message to the fuel pump/trailer brake control module. The fuel pump/trailer brake control module compares the states of the brake switch signal to the serial data message after a master cylinder brake pressure sensor threshold is exceeded. If the brake switch signal and the serial data message are not in agreement or if the serial data message is not valid, a DTC will set and the trailer brake control system will be disabled.

1. Battery voltage is 9.5-17 V.
2. The module initialization has taken place.
3. The master cylinder brake pressure exceeds threshold

1. The brake switch serial data message is not valid.
2. The actual brake switch input to the fuel pump/trailer brake control module, and the serial data information for the brake switch do not match.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center (DIC) will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The fuel pump/trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, press the brake pedal. The brake lights should illuminate and the Brake Switch Status parameter should indicate ON.

1. Verify that DTC B3445, C0277, C0297, or C0890 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Ignition OFF, disconnect the harness connector of the fuel pump/trailer brake control module.
3. Ignition ON, test for greater than 11 V between the IGN 1 voltage circuit terminal 15 and ground. If less than the specified voltage, test the IGN 1 voltage circuit for a short to ground or an open/high resistance. If the circuit test normal and the MISC - IGN fuse is open, test the signal circuit terminal 37 for a short to ground. If the circuit tests normal, test or replace the RUN/CRANK relay.
4. If all the circuits test normal, replace the fuel pump/trailer brake control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Relay Replacement (Attached to Wire Harness)»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) or «Relay Replacement (Within an Electrical Center)»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for fuel pump/trailer brake control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostics are used to determine whether or not there is a fault with the brake pressure or wheel speed data being received by the fuel pump/trailer brake control module over GMLAN serial data.

The loss of serial data brake pressure diagnostic is to determine whether or not there is a fault with the brake pressure data being received over GMLAN. This diagnostic looks at the brake pressure signal validity and protection value signals over a period of time to determine the fault state of the brake pressure sensor.

The loss of serial data wheel speed diagnostic is to determine whether or not there is a fault with the wheel speed data being received over GMLAN. This diagnostic looks at the wheel speed signal validity and sequence number errors over a period of time to determine the fault state

1. Ignition ON.
2. Ignition voltage is 9.5-17 V.

1. The EBCM diagnoses a fault condition in the master cylinder pressure sensor, and sends a serial data message to the fuel pump/trailer brake control module.
2. The EBCM diagnoses a fault condition in the wheel speed sensors, and sends a serial data message to the fuel pump/trailer brake control module.
3. The fuel pump/trailer brake control module losses communication with the EBCM.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center (DIC) will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The fuel pump/trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

1. Verify that DTC U0100, U0121, U0140, or U2099 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Verify that DTC C0035, C0040, C0045, C0050, OR C0131 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
3. Replace the fuel pump/trailer brake control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for fuel pump/trailer brake control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostics are used to determine whether or not there is a fault with the brake pressure or wheel speed data being received by the trailer brake control module (TBCM) over GMLAN serial data.

The loss of serial data brake pressure diagnostic is to determine whether or not there is a fault with the brake pressure data being received over GMLAN. This diagnostic looks at the brake pressure signal validity and protection value signals over a period of time to determine the fault state of the brake pressure sensor.

The loss of serial data wheel speed diagnostic is to determine whether or not there is a fault with the wheel speed data being received over GMLAN. This diagnostic looks at the wheel speed signal validity and sequence number errors over a period of time to determine the fault state

1. Ignition ON.
2. Ignition voltage is 9.5-17 V.

1. The EBCM diagnoses a fault condition in the master cylinder pressure sensor, and sends a serial data message to the trailer brake control module.
2. The EBCM diagnoses a fault condition in the wheel speed sensors, and sends a serial data message to the trailer brake control module.
3. The trailer brake control module losses communication with the EBCM.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The TBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

1. Verify that DTC U0100, U0121, U0140, or U2099 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
2. Verify that DTC C0035, C0040, C0045, C0050, OR C0131 are not set. If any of the DTCs are set, refer to «Diagnostic Trouble Code (DTC) List - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-trouble-code-dtc-list) .
3. Replace the trailer brake control module.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Trailer Brake Control Module Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for TBCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

The trailer brake control relay receives inputs from the fuel pump/trailer brake control module, these inputs are used to determine the amount of voltage the relay will supply to the trailer brakes.

1. Ignition ON.
2. Battery voltage is 9.5-17 V.
3. The module is powered up and completes initialization.

C0870 00

1. The trailer brake circuit reference voltage for the trailer brake control relay is below 4.8 V or above 5.2 V.

C1114 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the solid state relay output circuit.

C1119 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the relay feedback circuit.

C1112 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the integrated trailer brake relay control active low circuit.
2. The fuel pump/trailer brake control module detects an open in the battery positive voltage circuit to the trailer brake control relay.
3. The fuel pump/trailer brake control module detects an open in the ground circuit to the trailer brake control relay.
4. The fuel pump/trailer brake control module detects a short to ground or open in the solid state relay enable circuit.

C1113 01

1. The fuel pump/trailer brake control module detects a short to voltage in the solid state relay enable circuit.
2. The fuel pump/trailer brake control module detects a short to voltage in the trailer brake output supply voltage control circuit.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center will display Service Trailer Brake System.

Condition for Clearing the DTC

1. The condition for the DTC is no longer present.
2. The fuel pump/trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool trailer brake controls user gain parameter. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.

Note. These diagnostics are based on having no trailer connected.

1. Ignition ON, verify that DTC P2534 is not set. If the DTC is set, refer to «DTC P2534»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures) .
2. Ignition OFF, disconnect the harness connector at the solid state relay.
3. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal F and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the STUD 2 fuse is open, replace the trailer brake control relay.
5. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and ground. If test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
6. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and B+. If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the fuel pump/trailer brake control module.
7. Ignition ON, test for 3.2-4.1 V between the control circuit terminal C and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
8. Ignition ON, test for 3.2-4.1 V between the control circuit terminal A and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
9. Ignition ON, test for less than 1 V between the control circuit terminal D and ground. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
10. If all circuits test normal, replace the trailer brake solid state relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Trailer Brake Control Relay Replacement (1500)»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system) or «Trailer Brake Control Relay Replacement (2500)»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for fuel pump/trailer brake control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The trailer brake control relay receives inputs from the trailer brake control module (TBCM), these inputs are used to determine the amount of voltage the relay will supply to the trailer brakes.

1. Ignition ON.
2. Battery voltage is 9.5-17 V.
3. The module is powered up and completes initialization.

C0870 00

1. The trailer brake control module circuit reference voltage for the trailer brake control relay is below 4.8 V or above 5.2 V.

C1114 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the solid state relay output circuit.

C1119 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the relay feedback circuit.

C1112 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the integrated trailer brake relay control active low circuit.
2. The trailer brake control module detects an open in the battery positive voltage circuit to the trailer brake control relay.
3. The trailer brake control module detects an open in the ground circuit to the trailer brake control relay.
4. The trailer brake control module detects a short to ground or open in the solid state relay enable circuit.

C1113 01

1. The trailer brake control module detects a short to voltage in the solid state relay enable circuit.
2. The trailer brake control module detects a short to voltage in the trailer brake output supply voltage control circuit.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool trailer brake controls user gain parameter. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.

Note. These diagnostics are based on having no trailer connected.

1. Ignition ON, verify that DTC P2534 is not set. If the DTC is set, refer to «DTC P2534»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures) .
2. Ignition OFF, disconnect the harness connector at the solid state relay.
3. Test for less than 5 ohms between the ground circuit terminal B and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
4. Ignition OFF, verify that a test lamp illuminates between the B+ circuit terminal F and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the STUD 2 fuse is open, replace the trailer brake control relay.
5. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and ground. If test lamp illuminates, test the control circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
6. Ignition ON, verify that a test lamp does not illuminate between control circuit terminal E and B+. If test lamp illuminates, test the control circuit for a short to ground. If the circuit tests normal, replace the trailer brake control module.
7. Ignition ON, test for 3.2-4.1 V between the control circuit terminal C and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the trailer brake control module. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
8. Ignition ON, test for 3.2-4.1 V between the control circuit terminal A and ground. If less than the specified range, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the trailer brake control module. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
9. Ignition ON, test for less than 1 V between the control circuit terminal D and ground. If greater than the specified range, test the control circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
10. If all circuits test normal, replace the trailer brake solid state relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Trailer Brake Control Relay Replacement (1500)»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system) or «Trailer Brake Control Relay Replacement (2500)»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
2. «Trailer Brake Control Module Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
3. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for TBCM replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The fuel pump/trailer brake control module system has a control panel with the trailer gain and manual apply switches. The switches are located on the instrument panel to the left of the steering column. The control panel and switches allows you to adjust the amount of output, referred to as trailer gain, available to the electric trailer brakes and allows you to manually apply the trailer brakes. The Trailer Brake Control Panel, and switches are used along with the Trailer Brake Display Page on the Driver Information Center to adjust and display power output to the trailer brakes.

1. Battery voltage is 9.5-17 V.
2. The module is powered up and completes initialization.

C0880 00 or C0890 00

1. The fuel pump/trailer brake control module detects the 5 V reference circuit voltage is less than 4.8 V or greater than 5.2 V.

C1115 08 or C1115 5A

1. The fuel pump/trailer brake control module detects the manual apply switch is applied before the ignition is cycled OFF, and continuously applied for 30 seconds after ignition is cycled to ON.
2. The fuel pump/trailer brake control module detects the manual apply switch is applied continuously for 5 minutes.
3. The fault is detected if the manual apply switch input and redundant apply switch input exceeds a threshold for an extended amount of time.

C1116 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the manual apply signal circuit.
2. The fuel pump/trailer brake control module detects a open on the low reference circuit.

C1117 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the redundant manual apply signal circuit.
2. The fuel pump/trailer brake control module detects a short to voltage on the manual apply signal circuit.
3. The fuel pump/trailer brake control module detects a open on the low reference circuit.

C1118 00

1. The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the user gain signal circuit.
2. The fuel pump/trailer brake control module detects a open on the low reference circuit.

C1118 08

1. The fuel pump/trailer brake control module detects the user gain switch is applied before the ignition is cycled OFF, and continuously applied for 30 seconds after ignition is cycled to ON.
2. The fuel pump/trailer brake control module detects the user gain switch is applied continuously for 5 minutes.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center (DIC) will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The fuel pump/trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool trailer brake controls user gain parameter. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.

Note. These diagnostics are based on having no trailer connected.

1. Ignition ON, verify that DTC P2534 is not set. If the DTC is set, refer to «DTC P2534»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures) .
2. Ignition OFF, disconnect the harness connector at the trailer brake controller switch.
3. Test for less than 5 ohms between the low reference circuit terminal 8 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module.
4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground. If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the fuel pump/trailer brake control module. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
5. Verify the scan tool Manual Apply Switch parameter is less than 5 percent. If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 3. Verify the scan tool Manual Apply Switch parameter 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 fuel pump/trailer brake control module.
7. Verify the scan tool Redundant Manual Apply Switch parameter is greater than 90 percent. If less than the specified range, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
8. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the 5 V reference circuit terminal 3. Verify the scan tool Redundant Manual Apply Switch parameter is less than 2 percent. If greater 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 fuel pump/trailer brake control module.
9. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 6 and ground. 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 fuel pump/trailer brake control module. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the fuel pump/trailer brake control module.
10. If all circuits test normal, test or replace the trailer brake controller switch panel.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Trailer Brake Control Switch Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
2. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for fuel pump/trailer brake control module replacement, setup, and programming

1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
2. Review «Strategy Based Diagnosis»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
3. «Diagnostic Procedure Instructions»(/cadillac/escalade/gmt900-2006-2014/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The trailer brake control module (TBCM) system has a control panel with the trailer gain and manual apply switches, and is located on the instrument panel to the left of the steering column. The control panel and switches allows you to adjust the amount of output, referred to as trailer gain, available to the electric trailer brakes and allows you to manually apply the trailer brakes. The Trailer Brake Control Panel, and switches is used along with the Trailer Brake Display Page on the driver information center to adjust and display power output to the trailer brakes.

1. Battery voltage is 9.5-17 V.
2. The module is powered up and completes initialization.

C0880 00 or C0890 00

1. The TBCM detects the 5 V reference circuit voltage is less than 4.8 V or greater than 5.2 V.

C1115 08 or C1115 5A

1. The trailer brake control module detects the manual apply switch is applied before the ignition is cycled OFF, and continuously applied for 30 seconds after ignition is cycled to ON.
2. The trailer brake control module detects the manual apply switch is applied continuously for 5 minutes.
3. The fault is detected if the manual apply switch input and redundant apply switch input exceeds a threshold for an extended amount of time.

C1116 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the manual apply signal circuit.
2. The trailer brake control module detects a open on the low reference circuit.

C1117 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the redundant manual apply signal circuit.
2. The trailer brake control module detects a short to voltage on the manual apply signal circuit.
3. The trailer brake control module detects a open on the low reference circuit.

C1118 00

1. The trailer brake control module detects a short to ground, open or a short to voltage on the user gain signal circuit.
2. The trailer brake control module detects a open on the low reference circuit.

C1118 08

1. The trailer brake control module detects the user gain switch is applied before the ignition is cycled OFF, and continuously applied for 30 seconds after ignition is cycled to ON.
2. The trailer brake control module detects the user gain switch is applied continuously for 5 minutes.

1. The trailer brake control will be disabled for the remainder of the ignition cycle.
2. The driver information center (DIC) will display Service Trailer Brake System.

1. The condition for the DTC is no longer present.
2. The trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.

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

1. «Circuit Testing»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
2. «Connector Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
4. «Wiring Repairs»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Ignition ON, observe the scan tool trailer brake controls user gain parameter. The reading should be between 0-100 percent, and change with operating the gain switch up or gain switch down.

Note. These diagnostics are based on having no trailer connected.

1. Ignition ON, verify that DTC P2534 is not set. If the DTC is set, refer to «DTC P2534»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures) .
2. Ignition OFF, disconnect the harness connector at the trailer brake controller switch.
3. Test for less than 5 ohms between the low reference circuit terminal 8 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the trailer brake control module.
4. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 3 and ground. If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the trailer brake control module. If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
5. Verify the scan tool Manual Apply Switch parameter is less than 5 percent. If greater than the specified range, test the signal circuit terminal 4 for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
6. Install a 3 A fused jumper wire between the signal circuit terminal 4 and the 5 V reference circuit terminal 3. Verify the scan tool Manual Apply Switch parameter 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 trailer brake control module.
7. Verify the scan tool Redundant Manual Apply Switch parameter is greater than 90 percent. If less than the specified range, test the signal circuit terminal 5 for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
8. Install a 3 A fused jumper wire between the signal circuit terminal 5 and the 5 V reference circuit terminal 3. Verify the scan tool Redundant Manual Apply Switch parameter is less than 2 percent. If greater 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 trailer brake control module.
9. Ignition ON, test for 4.8-5.2 V between the signal circuit terminal 6 and ground. 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 trailer brake control module. If greater than the specified range, test the signal circuit for a short to voltage. If the circuit tests normal, replace the trailer brake control module.
10. If all circuits test normal, test or replace the trailer brake controller switch panel.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

1. «Trailer Brake Control Switch Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
2. «Trailer Brake Control Module Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/towing-systems/#trailer-brake-control-system)
3. «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for TBCM replacement, setup, and programming

Scheme 2

Removal Procedure

1. Turn the ignition switch to the OFF position.
2. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
3. Disconnect the trailer brake control module electrical connector.
4. Loosen, but do not remove, the trailer brake control module bolts (1).
5. Slide the trailer brake control module (1) rearward and remove the trailer brake control module.

Installation Procedure

1. If installing a new trailer brake control module, hand start the 3 trailer brake control module bolts.
2. Position the trailer brake control module to the frame rail.
3. Slide the trailer brake control module (1) forward on the frame rail.
4. Tighten the trailer brake control module bolts (1) to 9 N.m (80 lb in).
5. Connect the trailer brake control module electrical connector.
6. If installing a new trailer brake control module, program the module. Refer to «Control Module References»(/cadillac/escalade/gmt900-2006-2014/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) .

1. Turn the ignition switch to the OFF position.
2. Remove the spare tire and wheel assembly. Refer to «Spare Wheel Hoist Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/wheel-tire-system/#tires-wheels) .
3. Raise and support the vehicle. Refer to «Lifting and Jacking the Vehicle»(/cadillac/escalade/gmt900-2006-2014/remont/ignition-switchsteering-lock/#general-information__lifting-and-jacking-the-vehicle) .
4. Remove the fuel pump flow control module (1). Refer to «Fuel Pump Flow Control Module Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/testing-diagnostics/#engine-control-system-fuel-system-53l-60l-62l-repair-instructions) .
5. Remove the trailer brake control relay bolts (1).
6. Disconnect the electrical connector and remove the trailer brake control relay (1).

1. Connect the electrical connector and install the trailer brake control relay (1).
2. Install the trailer brake control relay bolts (1) and tighten to 6 N.m (53 lb in).
3. Install the fuel pump flow control module (1). Refer to «Fuel Pump Flow Control Module Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/testing-diagnostics/#engine-control-system-fuel-system-53l-60l-62l-repair-instructions) .
4. Install the spare tire and wheel assembly. Refer to «Spare Wheel Hoist Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/wheel-tire-system/#tires-wheels) .

1. Turn the ignition switch to the OFF position.
2. Remove the spare tire and wheel assembly. Refer to «Spare Wheel Hoist Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/wheel-tire-system/#tires-wheels) .
3. Disconnect the trailer brake control relay electrical connector.
4. Loosen, but do not remove, the trailer brake control relay bolts (1).
5. Slide the trailer brake control relay (1) toward the rear of the vehicle and remove the trailer brake control relay.

1. If installing a new trailer brake control relay, hand start the 2 trailer brake control relay bolts.
2. Position the trailer brake control relay to the frame rail.
3. Slide the trailer brake control relay (1) forward on the frame rail.
4. Tighten the trailer brake control relay bolts (1) to 6 N.m (53 lb in).
5. Connect the trailer brake control relay electrical connector.
6. Install the spare tire and wheel assembly. Refer to «Spare Wheel Hoist Replacement»(/cadillac/escalade/gmt900-2006-2014/remont/wheel-tire-system/#tires-wheels) .

Built Prior to 2010

This vehicle may be equipped with a Trailer Brake Control Module system for electric trailer brakes. The power output to the trailer brakes is based on the amount of brake pressure being applied in the vehicle's brake system. The available power output to the trailer brakes can be adjusted to a wide range of trailering situations.

Note. Connecting a trailer that is not compatible with the trailer brake system may result in reduced or complete loss of trailer braking. There may be an increase in stopping distance or trailer instability which could result in personal injury or damage to your vehicle, trailer, or other property. An aftermarket controller may be available for use with trailers with surge, air or electric-over-hydraulic trailer brake systems. To determine the type of brakes on your trailer and the availability of controllers, check with your trailer manufacturer or dealer. Do not power-up an aftermarket controller with the factory brake controller at the same time.

The vehicle is equipped with the following trailer braking components

1. Manual Trailer Brake Apply
2. Trailer Gain Adjustment
3. Trailer Brake Control Panel
4. Trailer Brake Driver Information Center Display

Built 2010 and After

Some trucks less than 3900 Kg (8600 lb) GVW with a gasoline engine may be equipped with a Trailer Brake Control Module (TBCM) or a combination Fuel Pump/Trailer Brake Control Module (FTCM) system for electric trailer brakes. Some trucks greater than or equal to 3900 Kg (8600 lb) GVW may be equipped with a integrated Trailer Brake Control Module (TBCM) system for electric trailer brakes. The power output to the trailer brakes is based on the amount of brake pressure being applied in the vehicle's brake system. The available power output to the trailer brakes can be adjusted to a wide range of trailering situations.

Note. Connecting a trailer that is not compatible with the trailer brake system may result in reduced or complete loss of trailer braking. There may be an increase in stopping distance or trailer instability which could result in personal injury or damage to your vehicle, trailer, or other property. An aftermarket controller may be available for use with trailers with surge, air or electric-over-hydraulic trailer brake systems. To determine the type of brakes on your trailer and the availability of controllers, check with your trailer manufacturer or dealer. Do not power-up an aftermarket controller with the factory brake controller at the same time.

The vehicle is equipped with the following trailer braking components

1. Manual Trailer Brake Apply
2. Trailer Gain Adjustment
3. Trailer Brake Control Panel
4. Trailer Brake Driver Information Center Display

Manual Trailer Brake Apply

The Manual Trailer Brake Apply Lever is located on the Trailer Brake Control Panel, and is used to apply the trailer's electric brakes independent of your vehicle's brakes. This lever is used in the Trailer Gain Adjustment Procedure to properly adjust the power output to the trailer brakes. Sliding the lever to the left will apply only the trailer brakes. The power output to the trailer is indicated in the Trailer Brake Display Page in the Driver Information Center. If your vehicle's service brakes are applied while using the Manual Trailer Brake Apply Lever, the trailer output power will be the greater of the two.

The trailer and the vehicle's brake lamps will come on when either vehicle braking or manual trailer brakes are applied.

Trailer Gain Adjustment

Trailer Gain should be set for a specific trailering condition, and must be adjusted any time vehicle loading, trailer loading or road surface conditions change.

Setting the Trailer Gain properly is needed for the best trailer stopping performance. A trailer that is over-gained may result in locked trailer brakes. A trailer that is under-gained may result in not enough trailer braking. Both of these conditions may result in poorer stopping and stability of the vehicle and trailer.

After the electrical connection is made to a trailer equipped with electric brakes, the TRAILER CONNECTED message will be momentarily displayed on the Driver Information Center. The Trailer Brake Display Page will appear on the Driver Information Center showing TRAILER GAIN and OUTPUT, after all vehicle related service messages are acknowledged by the driver. The dashed lines in the TRAILER OUTPUT display signifies a disconnected trailer or trailer brake fault condition, and will disappear only when the fault condition is not present.

Trailer Gain Adjustment

1. Adjust trailer gain in 0.5 step increments up to 10 gain setting by using the gain adjustment +/- buttons on the trailer brake control panel switch. Pressing and holding a gain button will cause the trailer gain to continuously increment or decrement. To turn the output to the trailer off, set the gain to zero.
2. Drive the tow vehicle and trailer combination on a level road surface representative of the towing condition, and free of traffic at approximately 32-40 km/h (20-25 mph) and fully apply the manual trailer brake apply lever mechanism located on the trailer brake control panel switch. Adjusting trailer gain at slower speeds may result in an incorrect gain setting.
3. Adjust the trailer gain to just below the threshold of trailer wheel lock-up. Important trailer wheel lock-up may not occur if towing a heavily loaded trailer. In this case, adjust the trailer gain to the highest allowable setting for the towing condition.

Trailer Brake Control Panel

The trailer brake system has a control panel with the trailer gain and manual apply switches, and is located on the instrument panel to the left of the steering column. The control panel and switches allows you to adjust the amount of output, referred to as trailer gain, available to the electric trailer brakes and allows you to manually apply the trailer brakes. The Trailer Brake Control Panel, and switches is used along with the Trailer Brake Display Page on the Driver Information Center to adjust and display power output to the trailer brakes.

Driver Information Indicators and Messages

The following indicators are used to inform the driver of several different factors.

Trailer Connected

This message will be briefly displayed when a trailer with electric brakes is first connected to the vehicle. This message will automatically turn off in about ten seconds. The driver can also acknowledge this message before it automatically turns off.

Check Trailer Wiring And Trailer Not Connected

This message will be displayed if

1. The system detects a trailer with electric brakes is connected to the vehicle, and then the trailer harness becomes disconnected from the vehicle. If a trailer connection is made initially and the vehicle or trailer wiring connections is not correct the TRAILER NOT CONNECTED message will be displayed during the ignition key up as if there is no trailer connected.
2. The trailer connection is recognized initially and then a disconnect occurs while the vehicle is stationary, this message will automatically turn off in about thirty seconds. This message will also turn off if the driver acknowledges this message off or if the trailer harness is reconnected.
3. A disconnect of the trailer wiring harness occurs while the vehicle is moving, the CHECK TRAILER WIRING message will continue until the ignition is turned off. This message will also turn off if the driver acknowledges this message off or if the trailer harness is re-connected or repairs are completed.
4. There is an electrical fault in the wiring to the electric trailer brakes. The CHECK TRAILER WIRING message will continue as long as there is an electrical fault in the trailer wiring. This message will also turn off if the driver acknowledges this message off.

Service Trailer Brake System

This message will be displayed when there is a problem with the trailer brake control system. If this message persists over multiple ignition cycles there is a concern with the trailer brake system. Take your vehicle to an authorized GM dealer to have the trailer brake system diagnosed and repaired.

Trailer Gain And Output Display

This display menu can be accessed by scrolling through the Driver Information Center menu, or any time the trailer gain +/- button is depressed, or the manual trailer brake apply lever is actuated. The trailer gain display is 0 to 10 in 0.5 step increments, and indicates the current user setting of the trailer output gain. The trailer output is 0 to 10 bars in 1 bar increments, and indicates the output power provided to the trailer brakes, relative to the gain setting.

See also:
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Component Connector End Views
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Trouble Code (DTC) List - Vehicle
• Diagnostic Repair Verification
• Relay Replacement (Attached to Wire Harness)
• DTC P2534
• Knee Bolster Replacement (Cadillac)
• Lifting and Jacking the Vehicle
• Fastener Caution
• Spare Wheel Hoist Replacement
• Fuel Pump Flow Control Module Replacement
• DTC B3894 (Gasoline With LY6, or Diesel)