Circuit Description
The system relay is energized when the ignition is ON. The system relay supplies voltage to the valve solenoids and the pump motor. This voltage is referred to as the system voltage. The electronic brake control module (EBCM) microprocessor activates the valve solenoids by grounding the control circuit.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C0269 Excessive Dump Time |
| • | DTC C0274 Excessive Isolation Time |
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The vehicle is experiencing an ABS event. |
Conditions for Setting the DTC
C0269
The EBCM commands a dump solenoid ON for 9 consecutive seconds.
C0274
The EBCM commands an isolation solenoid ON for 255 consecutive seconds.
Action Taken When the DTC Sets
If equipped, the following actions may occur:
| • | The EBCM disables the ABS/TCS/DRP. |
| • | The ABS indicator turns ON. |
| • | The TRACTION OFF indicator turns ON. |
| • | The red brake warning indicator turns ON. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Diagnostic Aids
The most likely cause of DTC C0269 or DTC C0274 is a mechanical failure that causes a wheel to lock and remain locked. The DTCs may also set, conceivably, when the ABS is activated on surfaces that are nearly impossible to get traction on. If the DTC sets within these conditions, diagnosis of the ABS system is not necessary.
Test Description
The number below refers to the step number on the diagnostic table:
Step | Action | Yes | No |
|---|---|---|---|
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | |
Do the Solenoid Tests show the system to be functioning normally? | Go to Diagnostic Aids | Go to Step 3 | |
3 | Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Replacement . Did you complete the replacement? | Go to Step 4 | -- |
4 | Use the scan tool in order to perform the necessary Solenoid Tests. Do the Solenoid Tests show the system to be functioning normally? | System OK | Go to Step 3 |
