3. Test for less than 5 ohm between the ground circuit terminal B and ground.
锟斤拷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.
锟斤拷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.
锟斤拷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+.
锟斤拷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.
锟斤拷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.
锟斤拷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.
锟斤拷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.
锟斤拷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.
锟斤拷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.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Trailer Brake Control Relay Replacement (1500) (See: Accessories and Optional Equipment/Towing / Trailer System/Trailer Towing
Relay/Service and Repair/Trailer Brake Control Relay Replacement (1500))Trailer Brake Control Relay Replacement (2500) (See:
Accessories and Optional Equipment/Towing / Trailer System/Trailer Towing Relay/Service and Repair/Trailer Brake Control Relay
Replacement (2500))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for fuel pump/trailer brake control module
replacement, setup, and programming
Gasoline With LY6, or Diesel
DTC C0870, C1112, C1113, C1114, or C1119 (Gasoline With LY6, or Diesel)
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC C0870 00
- Device Voltage Reference Output 1 Circuit
