Engine Electrical
DTC C0800
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Initial Inspection and Diagnostic Overview) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Initial Inspection and Diagnostic Overview) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Initial Inspection and Diagnostic Overview) provides an overview of each diagnostic category.
DTC Descriptors
DTC C0800 03
- Device Power Circuit Below Threshold - TBCM
DTC C0800 07
- Device Power Circuit Above Threshold - TBCM
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The trailer brake control module (TBCM) monitors the 12V system voltage to make sure that the voltage stays within the proper range. Damage to components, and incorrect data can occur when the voltage is out of range. The TBCM monitors the system voltage. If the TBCM detects a 12V system voltage outside an expected range, DTC C0800 will set.
Conditions for Running the DTC
C0800 03
* Ignition is in RUN.
* The system relay is commanded ON.
C0800 07
* Ignition is in RUN.
* The vehicle speed is greater than 8 km/h (5 mph).
Conditions for Setting the DTC
C0800 03
* During initialization or when the system is inactive, the system voltage is less than 10.5 volts.
* During the system operation, the system voltage is less than 9 volts.
C0800 07
* Ignition is in RUN.
* The system voltage is greater than 18.5 volts.
Action Taken When the DTC Sets
* The driver information center (DIC) displays the SERVICE BRAKES SOON warning message.
* The TBCM disables all functionality.
Conditions for Clearing the DTC
* The condition for the DTC is no longer present.
* The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.
Diagnostic Aids
A high or low voltage DTC in multiple modules indicates a concern in the charging system. Refer to Charging System Test (Charging System Test) .
Reference Information
Schematic Reference
* Trailer Brake Control Schematics ([1][2]Electrical Diagrams)
* Starting and Charging Schematics (Starting and Charging Schematics)
* Power Distribution Schematics (Power Distribution Diagrams)
* Ground Distribution Schematics (Ground Distribution Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
* Trailer Brake Controls Description and Operation (Trailer Brake Controls Description and Operation)
* Charging System Description and Operation (Description and Operation)
Electrical Information Reference
* Circuit Testing (Component Tests and General Diagnostics)
* Connector Repairs (Component Tests and General Diagnostics)
* Testing for Intermittent Conditions and Poor Connections (Component Tests and General Diagnostics)
* Wiring Repairs (Component Tests and General Diagnostics)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Engine running, accessories OFF, measure and record the battery voltage at the battery terminals. The voltage should be between 12.6 and 15.0 volts.
• If not within the specified range, refer to Charging System Test (Charging System Test) .
2. Observe the scan tool TBCM Battery Voltage parameter. The reading should be between 12.60 and 15.00 volts.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the TBCM.
2. Ignition OFF and scan tool disconnected, open and close the drivers door, and wait 1 minute. Test for less than 5 ohms between the ground circuit terminal 1 and ground.
• If greater than the specified range, test the ground circuit for an open/high resistance.
3. Verify that a test lamp illuminates between the B+ circuit terminal 32 and ground.
• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
4. If all circuits test normal, replace the TBCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
Control Module References (Programming and Relearning) for TBCM replacement, setup, and programming