C0221

DTC C0220-C0229

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 C0220
- Left Front ABS Channel in Release Too Long

DTC C0221
- Right Front ABS Channel in Release Too Long

DTC C0228
- Left Rear ABS Channel in Release Too Long

DTC C0229
- Right Rear ABS Channel in Release Too Long




Circuit/System Description

The system relay is energized when the ignition is ON. The system relay supplies voltage to the valve relay. 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 microprocessor activates individual valve solenoids by grounding the valve solenoid control circuits.


Conditions for Running the DTC

* Ignition voltage is greater than 8 volts.
* The system is in a ABS braking event.



Conditions for Setting the DTC

This code is set when the following criteria are met.

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



Action Taken When the DTC Sets

* The EBCM disables the ABS system.
* The ABS indicator illuminates.
* DRP function is degraded.



Conditions for Clearing the DTC

* The condition for the DTC is no longer present.
* The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.



Diagnostic Aids

Always diagnose and repair any wheel speed sensor failures prior to diagnosing DTCs C0220, C0221, C0228 or C0229. These DTCs in theory may be set on surfaces that are nearly impossible to get traction on. If the DTC sets within these conditions, diagnosis of the ABS system may not be necessary.


Reference Information
Schematic Reference

Antilock Brake System Schematics ([1][2]Antilock Brakes / Traction Control Systems)
Connector End View Reference

Component Connector End Views
Description and Operation

ABS Description and Operation (Description and Operation)
Electrical Information Reference

* Circuit Testing
* Connector Repairs
* Testing for Intermittent Conditions and Poor Connections
* Wiring Repairs

Scan Tool Reference

Control Module References for Scan Tool Information


Circuit/System Testing

1. Ignition OFF, disconnect the harness connector at the EBCM.
2. Test for less than 5 ohm of resistance between the ground circuit terminal E and ground.

• If greater than the specified range, test the ground circuit for an open/high resistance.

3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminals A and B and ground.

• If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test or replace the BPMV.

4. Ignition ON, use the scan tool to perform the solenoid test.

• If solenoid test failed, replace the EBCM.

5. If all circuits test normal, replace the BPMV.



Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

* Brake Pressure Modulator Valve Replacement (Without RPO LAT) (Service and Repair)Brake Pressure Modulator Valve Replacement (With RPO LAT) (Service and Repair)
* Control Module References for EBCM replacement, setup, and programming