Testing Notes

CAUTION: When checking resistance in the RABS II system, always disconnect the battery ground cable. Improper resistance readings may occur with the vehicle battery connected.

This procedure is intended to determine whether the cause for loss of or erratic Programmable Speedometer/Odometer Module (PSOM) function is due to the lack of a signal from the rear axle sensor.

There are two basic reasons that PSOM would not receive a signal from the rear axle sensor:

1. The rear axle sensor or the signal from the rear axle sensor is faulty and either not being generated or is not reaching the antilock electronic control unit and/or PSOM. In cases where the concern is not intermittent and not reaching the antilock electronic control unit, the ABS warning light will be on upon vehicle start up and a rear axle diagnostic trouble code should be obtained upon RABS II diagnostic trouble code retrieval. [1][2]Displaying and Reading Trouble Codes Where the concern is intermittent and the ABS warning light does not come on during vehicle start up, a rear sensor diagnostic trouble code may still be stored in the antilock electronic control unit (see RABS II Diagnostic Codes). [1][2]Diagnostic Trouble Code Descriptions

2. The wiring or interconnections in the vehicle harness between the antilock electronic control unit and the PSOM module is faulty. This may lead to erratic PSOM function and is difficult to diagnose.

This procedure will only determine whether the rear axle sensor is functioning based upon whether a signal is received at the PSOM module. If it is determined that the rear axle sensor is sending out a proper signal, test the programmable speedometer/odometer module.