C0294
DTC C0294, C120C, or C12F8
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (with HP2) (Initial Inspection and Diagnostic Overview)Diagnostic System Check - Vehicle (without HP2) (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 C0294 00
- BMC Primary Piston Position Sensor A and B Correlation
DTC C120C
- BMC Primary Piston Position Sensor A and B Correlation
DTC C12F8
- BMC Primary Piston Position Sensor A and B Correlation
Diagnostic Fault Information
Circuit/System Description
The electronic brake control module (EBCM) uses input from the brake master cylinder piston position sensor and the brake switch to determine when the brake pedal is being applied and with how much force. These inputs are used to determine the driver's braking intent which is used to the control amount of pressure applied to the wheels.
Conditions for Running the DTC
* Ignition ON.
* Ignition voltage is greater than 10 volts.
Conditions for Setting the DTC
* The EBCM detects an open in the low reference circuit.
* The EBCM detects that the two signal circuits do not match each other.
Action Taken When the DTC Sets
* The EBCM disables the antilock brake system (ABS), traction control and the vehicle stability enhancement system (VSES) for the duration of the ignition cycle.
* A DIC message and/or a warning indicator may be displayed.
Conditions for Clearing the DTC
* The condition for the DTC is no longer present.
* The EBCM clears the history DTC when a current DTC is not detected in 40 consecutive drive cycles.
Reference Information
Schematic Reference
Antilock Brake System Schematics (Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
ABS 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
Ignition ON, use a scan tool to observe the EBCM BMC Primary Piston Position Sensor A and B parameter while applying and releasing the brake pedal. The voltage should change between 0 and 5 volts.
Circuit/System Testing
1. Ignition OFF, disconnect the harness connector at the brake master cylinder piston position sensor.
2. Ignition OFF, test for less than 5 ohm between the low reference circuit terminal 4 and ground.
• If greater than the specified range, test the low reference circuit for an open/high resistance.
3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 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 greater than the specified range, test the 5-volt reference circuit for a short to voltage.
4. Verify the scan tool BMC Primary Piston Position Sensor A parameter is less than 1 volt.
• If greater than the specified range, test the signal circuit terminal 1 for a short to voltage.
5. Install a 3A fused jumper wire between the signal circuit terminal 1 and the 5-volt reference circuit terminal 2. Verify the scan tool BMC Primary Piston Position Sensor A parameter is greater than 4.5 volts.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance.
6. Verify the scan tool BMC Primary Piston Position Sensor B parameter is less than 1 volt.
• If greater than the specified range, test the signal circuit terminal 3 for a short to voltage.
7. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool BMC Primary Piston Position Sensor B parameter is greater than 4.5 volts.
• If less than the specified range, test the signal circuit for a short to ground or an open/high resistance.
8. If all circuits test normal, replace the brake master cylinder piston position sensor. If DTC resets, replace the EBCM.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Brake Master Cylinder Primary Piston Position Sensor Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming