C0274

Circuit Description (DTC C0269)
The EBCM microprocessor grounds the dump coil to energize and close the dump valve. This will release excessive brake pressure which was applied by the driver the wheels. If the EBCM microprocessor generates a dump command on one or more wheel for more than 9 seconds, the DTC will set (C0269).

Circuit Description (DTC C0274)
The EBCM microprocessor grounds the isolation coil to energize and close the isolation valve. This will prevent any additional brake pressure applied by the driver from reaching the wheel. Further increases in brake pressure will be prohibited. Each isolation valve is closed independently to isolate each wheel. The EBCM microprocessor also uses a software subroutine to monitor for any ABS event which would initiate an isolation command. This subroutine is performed every 1.0 second.

Conditions for Running the DTC (C0269 / C0274)
^ The ignition switch is in the RUN position.
^ The bulb check is complete.

Conditions for Setting the DTC (C0269)
^ Locked rotors
^ Braking on excessively slippery surfaces for greater than 9 seconds

Conditions for Setting the DTC (C0274)
Isolation time (pressure hold) exceeding 255 consecutive 1.0 second checks.

Action Taken When the DTC Sets (C0269)
If the EBCM microprocessor generates a dump command for greater than 9 seconds, this feature will be activated. If either front channel detects excessive dumping, the system will revert to rear only ABS. If the rear channel detects excessive dumping, all ABS activity stops.
DTC C0269 is an ignition latched DTC, which indicates that the above actions remain true until the ignition switch is turned to the OFF position (even if the cause of the DTC is intermittent).
DTC C0269 is a DRP critical DTC, which means that DRP is disabled and the BRAKE indicator lamp will also light.

Action Taken When the DTC Sets (C0274)
^ The ABS indicator lamp turns on.
^ The ABS disables.
DTC C0274 is an ignition latched DTC, which indicates that the above actions remain true until the ignition switch is turned to the OFF position (even if the cause of the DTC is intermittent).

Conditions for Clearing the DTC (DTCs C0269 / C0274)
^ Repair the conditions responsible for setting the DTC.
^ Use the Scan Tool Clear DTCs function.

Diagnostic Aids
Repair any other DTCs first. Then perform the Function Test of the scan tool in order to ensure proper operation of the ABS.

Test Description
The numbers below refer to the steps in the diagnostic table:
2. Using the scan tool Function Test to cycle the hydraulic valves in the BPMV, this step attempts to free a stuck hydraulic valve in the BPMV.