C0890

DTC C0890

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptor
DTC C0890
- Device Voltage Reference Output 3 Circuit

Diagnostic Fault Information





Circuit/System Description

The TBCM runs this diagnostics to check whether there is a fault on the internal TBCM 5 volt references used to monitor the Manual Apply switch circuits. This diagnostics checks if the circuits 5-volt references is within a range for normal operation.

Conditions for Running the DTC

* The system voltage is in the range of 9.5-17 volts.
* The module initialization has taken place.

Conditions for Setting the DTC

The TBCM detects voltage greater than 5.2 volts in the manual apply switch 5-volt reference circuit.

The TBCM detects voltage less than 4.8 volts in the manual apply switch 5-volt reference circuit.

Action Taken When the DTC Sets

* The trailer brake control will be disabled at the end of the current brake apply for the remainder of the ignition cycle.
* A message center or an indicator displays.

Conditions for Clearing the 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 or the antilock brake control system, diagnose them first before to resolve DTCs described in this section.


Circuit/System Testing

Important: All electrical components and accessories must be turned OFF and allowed to power down.

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 5 and ground.

* If greater than the specified range, test the ground circuit for an open/high resistance. 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. If all circuits test normal, test or replace the trailer brake controller switch panel.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

Refer to Programming and Relearning for TBCM setup and programming. Programming and Relearning