A085
ModerateA085 — Implausible Vehicle Speed Signal in the CAS Module
Description
What the Code Means
The CAS (Car Access System) module receives the vehicle speed signal from the DSC or ABS unit. CAS uses this signal for automatic door locking and anti-theft logic.
Code A085 flags a fault in that signal. Causes include a failed wheel speed sensor, damaged wiring, or a communication problem between modules.
Symptoms
Symptoms
- speedometer malfunction;
- automatic door locking doesn't engage;
- cruise control problems;
- warning lights on the instrument cluster.
Causes and fixes
Diagnosis and Repair
- Read fault codes from the DSC/ABS module (ISTA, INPA).
- Check the wheel speed sensors and their wiring.
- Check the signal with an oscilloscope or through ISTA.
- Replace the faulty sensor or repair the wiring.
- Clear the codes and take a test drive to confirm the repair.
Possible secondary damage
Secondary Problems
- losing the speed signal can affect ABS, DSC, and automatic transmission shift points — that makes for unsafe driving conditions;
- CAS may disable some of the car's comfort functions.