C1121

DTC C1120 or C1121

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 C1120 00
- Left Front Brake Hydraulic Circuit Blocked

DTC C1121 00
- Left Front Brake Hydraulic Circuit Leaking




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.
* The EBCM has run test on each of the 3 circuits (Left, Right, Rear) at least once.



Conditions for Setting the DTC

C1120 00

The EBCM is commanding a valve solenoid to release brake pressure. The wheel that is commanded to release brake pressure has a speed less than 5 km/h (3 mph) for 1.25 seconds.

C1121 00

The pressure change of the accumulator indicates the volume of fluid used which is compared to expected fluid used during a brake apply. Too much fluid usage indicates a leaking circuit


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

1. Ignition ON, verify that DTC C1120 or C1121 are not set.

• If DTCs are set, Check for hydraulic leaks. Refer to Symptoms - Hydraulic Brakes (Symptoms - Hydraulic Brakes)

2. Replace the brake pressure modulator valve (BPMV). If the DTC resets, replace the EBCM. .



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