1, 2 and 3 Digit Codes: 8

Fault Codes 5 through 8 Diagnosis Chart:

Wheel Speed Sensor Circuits:

SENSOR OPERATION
Each wheel speed sensor creates a small AC voltage as a toothed sensor ring (tone-wheel) is passed by the stationary sensor. The sensor ring is mounted on the drive axle or hub/bearing assembly. The sensor has a permanent magnet and coil and generates voltage by magnetic induction. Wheel speed determines the frequency of the wheel speed sensor signal. The Anti-lock Brake Control Module (ABM) uses the wheel speed sensor signal to calculate vehicle reference speeds and individual speed, acceleration, and slip values for each wheel. These values are used to determine when anti-lock control is required.

SENSOR CABLES
Proper installation of wheel speed sensor cables is critical to continued system operation. Be sure that cables are installed and routed properly. Failure to install cables in retainers, see COMPONENT REPAIR AND REPLACEMENT PROCEDURES, may result in contact with moving parts or overextension of cables, resulting in an open circuit.

FAILURE CONDITIONS
Fault codes 5-8 will set in case of intermittent or continuous low output. If a low output condition is detected during a hard acceleration, codes 5-8 cannot set; codes 9 and 10 will set instead.

*** UPDATED BY TSB #05-08-90 NOV. 5, 1990

NOTE: Some vehicles have been found with the cold solder joints on the vehicle harness side of the wheel speed sensor connector. Since this is a molded connector, diagnosis may be difficult.

Identify the suspect sensor through the fault code reading. Install the MST6100 Anti-lock Brake System (ABS) tester to the 35-way connector in the trunk and plug the cable into the pin-out box. Plug the leads of an Ohmmeter or suitable continuity tester into the terminals for the suspect wheel speed sensor (see chart).

Gain access to the suspected wheel speed sensor connector (the rear sensor connectors are accessed under the car by pulling the grommet from the body; the front sensor connectors are accessed by removing the sensor grommet retainer in the front wheel well and pulling the grommet from the body). Gently bend and twist the connector while reading the ohmmeter for continuity. If continuity is lost at any time, the connector should be replaced.