C1126

DTC C1124-C1126

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 C1124 00
- Base Brake Hydraulic Circuit Normally Open Valve

DTC C1125 00
- Hydraulic Circuit Test Duration Excessive

Circuit/System Description

The electronic brake control module EBCM) activates the valve relay to supply voltage to the valve solenoids. This voltage is referred to as the system voltage. The EBCM activates individual valve solenoids by grounding the valve solenoid control circuits.

Conditions for Running the DTC

* Ignition ON.
* The ignition voltage is greater than 10 volts.

Conditions for Setting the DTC

C1124 00

The EBCM detects that a BPMV internal valve has been blocked, closed, or stuck shut.

C1125 00

This code is an information code only, and requires no diagnostics.

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 Testing

1. Verify the 12V battery state of charge is above 12V.

• If the battery state of charge is low, charge the 12V battery. Refer to Battery Charging (Service and Repair).

2. Using the scan tool, perform the EBCM relearn.
3. Start the engine and allow it to idle.
4. Place the transmission in the PARK position.

Note: To ensure the complete brake modulator and high pressure accumulator (HPA) pressure relief procedure is allowed to occur; the brake controller must see one brake pedal apply with the engine running followed by a proper shutdown without applying the brake pedal.

5. Apply and release the brake pedal.

Note: The ignition must transition to the OFF position without pausing at ACCESSORY and without applying the brake pedal. This ensures that the brake modulator and HPA pressure relief occurs. This process will take approximately 1-3 minutes.

6. Turn the ignition OFF without pausing at ACCESSORY and without applying the brake pedal. Remove the key from the ignition.
7. Wait 3 minutes until the brake modulator and HPA pressure relief is complete.

Note: The ignition must remain in the ON position with the engine OFF during this entire procedure.

8. Ignition ON, brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:

* Master Cylinder Pressure Sensor Input -Less than 100 KPA (15 PSI)
* Rear Brake Pressure Sensor -Less than 100 KPA (15 PSI)
* Brake Pressure Sensor Input -Less than 100 KPA (15 PSI)
* Accum. Pressure Sensor -Less than 100 KPA (15 PSI)

• If any of the parameters are not within the specified range, replace the EBCM.

9. Brakes unapplied, verify the following EBCM scan tool parameters are within the specified values:

* BMC Prim. Piston Pos. Sen. 5V Reference Position -Between 4.75 V and 5.25 V
* BMC Primary Piston Position Sensor A -Less than.8V
* BMC Primary Piston Position Sensor B -Greater than 4.2V

• If any of the parameters are not within the specified range, refer to DTC C0277, C120C, C129A, C129B, C129D, C129E, C12B1, or C12F8 (C0277)

Repair Instructions

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

* Brake Pressure Modulator Valve Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for EBCM replacement, setup, and programming