Circuit 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.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | 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 |
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
If equipped, the following actions occur:
| • | The EBCM disables the ABS system. |
| • | The ABS indicator turns ON. |
| • | The driver information center (DIC) displays the Service ABS System message. |
| • | The traction control system (TCS) is disabled. |
| • | The DIC displays the Service Traction System Message. |
| • | The vehicle stability enhancement system (VSES) is disabled. |
| • | The DIC displays the Service Stability System Message. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | 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.
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Are any wheel speed related DTCs set? | Go to Step 3 | ||
3 |
Do the solenoids in question function normally? | Go to Diagnostic Aids | Go to Step 4 |
4 | Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Replacement . Did you complete the repair? | Go to Step 5 | -- |
5 | Use the scan tool and perform the solenoid test. Do the solenoids in question function normally? | System OK | Go to Step 2 |
