Gasoline Without LY6
DTC C0870, C1112, C1113, C1114, or C1119 (Gasoline Without LY6)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC C0870 00
- Device Voltage Reference Output 1 Circuit
DTC C1112 00
- Trailer Brake Control Relay Low Control Circuit
DTC C1113 01
- Trailer Brake Control Relay High Control Circuit Short to Battery
DTC C1114 00
- Trailer Brake Control Solenoids Control Circuit
DTC C1119 00
- Trailer Brake Control Relay Feedback Circuit
Diagnostic Fault Information
Circuit/System Description
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.
Conditions for Running the DTC
* Ignition ON.
* Battery voltage is 9.5-17 V.
* The module is powered up and completes initialization.
Conditions for Setting the DTC
C0870 00
The trailer brake circuit reference voltage for the trailer brake control relay is below 4.8 V or above 5.2 V.
C1112 00
* 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.
* The fuel pump/trailer brake control module detects an open in the battery positive voltage circuit to the trailer brake control relay.
* The fuel pump/trailer brake control module detects an open in the ground circuit to the trailer brake control relay.
* The fuel pump/trailer brake control module detects a short to ground or open in the solid state relay enable circuit.
C1113 01
* The fuel pump/trailer brake control module detects a short to voltage in the solid state relay enable circuit.
* The fuel pump/trailer brake control module detects a short to voltage in the trailer brake output supply voltage control circuit.
C1114 00
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
The fuel pump/trailer brake control module detects a short to ground, open or a short to voltage on the relay feedback circuit.
Action Taken When the DTC Sets
* The trailer brake control will be disabled for the remainder of the ignition cycle.
* The driver information center will display Service Trailer Brake System.
Condition for Clearing the DTC
* The condition for the DTC is no longer present.
* The fuel pump/trailer brake control module clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.
Diagnostic Aids
Inspect the trailer brake output supply voltage control circuit (dark blue wire circuit 47) that runs from the trailer brake relay to the 7-pin trailer connector in the bumper for water intrusion or corrosion.
Reference Information
Schematic Reference
Trailer Brake Control Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector End Views By Name)
Description and Operation
Trailer Brake Controls Description and Operation (Trailer Brake Controls)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
Scan Tool Reference
Control Module References (Control Module References) for scan tool information
Circuit/System Verification
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.
Circuit/System Testing
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 (Wiring Systems and Power Management).
2. Ignition OFF, disconnect the harness connector at the trailer brake control relay.
3. Test for less than 5 ohm 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 control relay.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Trailer Brake Control Relay Replacement (1500) (Trailer Brake Control Relay Replacement (1500))Trailer Brake Control Relay Replacement (2500, 3500 Pickup) (Trailer Brake Control Relay Replacement (2500, 3500 Pickup))Trailer Brake Control Relay Replacement (3500 Chassis Cab) (Trailer Brake Control Relay Replacement (3500 Chassis Cab))
* Control Module References (Control Module References) for fuel pump/trailer brake control module replacement, programming and setup