Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC C0800 03: Device Power Circuit Below Threshold - TBCMDTC C0800 07: Device Power Circuit Above Threshold - TBCM
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
B+ | C0800 03 | C0800 03 | -- | -- |
Ground | -- | C0800 03 | -- | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Ignition ON, engine OFF. Parameter Normal Value: 12.60 Volts | |||
B+ | 0.00 Volts* | 0.00 Volts* | 12.60 Volts |
*The scan tool will not communicate with the TBCM if there is 0 Volts on the circuit. | |||
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.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Electrical Information Reference
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- 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.
- Observe the scan tool TBCM Battery Voltage parameter. The reading should be between 12.60 and 15.00 volts.
| ⇒ | If not within the specified range, refer to Charging System Test. |
Circuit/System Testing
- Ignition OFF, disconnect the harness connector at the TBCM.
- 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.
- Verify that a test lamp illuminates between the B+ circuit terminal 32 and ground.
- If all circuits test normal, replace the TBCM.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
Control Module References for TBCM replacement, setup, and programming
