Subject: False wheel speed sensor codes

Vehicles Involved: All vehicles equipped Anti-lock brakes.


When performing brake, suspension or drive train system diagnostics or service, it is possible to set a false diagnostic trouble code ( DTC ) if the wheel(s) are rotated with the ignition switched on. If a wheel speed sensor DTC is set, the system warming lamp will illuminate and the ABS computer will store the fault code. NOTE: Warning lamp illumination signifies that the computer has detected a system malfunction and that the Anti-lock system is disabled. The ABS warning lamp will remain illuminated until the speed sensor code is cleared from computer memory. To clear a wheel speed sensor DTC from the ABS computer it may be necessary to use one of the following methods; Cycle the ignition switch off and on, drive the vehicle over 25 km, ground the diagnostic test terminal in a particular sequence or use a scan tool. Refer to a current version of the manufacturer’s Anti-lock brake system service manual for the procedure on a specific vehicle.



Once the code has been cleared, the ABS warning lamp will remain off and the ABS is now operational. On some systems the DTC(s) may remain stored in the history portion of the ABS computer. These code(s) remain in computer memory until, either the vehicle has been driven a predetermined number of drive cycles or the vehicles ignition has been cycled a number of times.
On some systems a scan tool can be used to clear code(s) from history portion of the memory.

To eliminate the possibility of false wheel speed sensor codes during servicing, always ensure the ignition is in the off position prior to rotating the wheel(s).