DTC A054: Rear Channel In Release Too Long

REAR CHANNEL IN RELEASE TOO LONG





Circuit Description
This DTC will diagnose a motor that is energized longer than expected. This could occur if a wheel speed sensor is malfunctioning, the motor does not turn, or the motor wires are crossed.

Diagnosis
The system monitors the total time in which the rear axle release mode is commanded. This test fails under the following conditions:
- The difference between the reference speed and the maximum rear speed exceeds 11 km/h (7 mph) while the rear channel is in release for more than 3 seconds.
- The difference between the reference speed and the maximum rear speed is less than 11 km/h (7 mph) while the rear channel is in release for more than 4 seconds.

Cause(s)
- The rear axle wheel speed sensor or the wiring shorted together during ABS operation.
- The motor pack assembly is faulty.

Fail Action
This is a critical operational fault. The ABS is disabled and the ABS warning lamp is turned on. A rehome is commanded to ensure that the motors are in the home position.

Test Description
The number(s) below refer to step(s) on the diagnostic table.
2. This step identifies a problem in a wheel speed sensor that may cause the system to be in release too long.
3. This checks for a wheel that may stick or bind because of a mechanical fault.
4. This checks to see if the motor is capable of moving and applying the hydraulic piston for the rear wheels.
5. This step ensures that the motor wiring is not crossed.
6. This isolates the fault of a "no-apply" situation to either the motor pack or the hydraulic modulator.

Diagnostic Aids
An intermittent malfunction in this DTC may result from a mechanical part of the system that sticks or binds.
Check the frequency of the malfunction by using the enhanced diagnostic feature of the scan tool as described in "Scan Tool Diagnostics." Scan Tool Diagnostics Use the scan tool to perform the hydraulic test to ensure that the total brake system is functional.
Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wiring connections, or physical damage to the wiring harness.

Important: Excessive drag or high resistance in the base brake or suspension system must be inspected and corrected before proceeding with DTC analysis.





DTC A054 - Rear Channel in Release Too Long