Antilock Braking System (ABS)

Circuit Diagram:

ANY TWO WHEEL SPEEDS ARE 0 KPH (0 MPH)
The four wheel speed sensors monitor the speed of each wheel by placing a magnetic coupling next to a ring mounted on the axle of each front wheel and in the hub and bearing of each rear wheel. The signal changes with the wheel speed. If the wheel speed signal is seen at 0 mph on any two wheels while the car is moving the control module will disable all ABS and turn on the Antilock telltale.

CODE PARAMETERS
Code 31 sets if:
^ Any two wheel speeds are 0 k/mh (0 mph) for 60 seconds
^ This code can set anytime vehicle is moving faster then 16 km/h (10 mph) and not in ABS braking.
^ The vehicle should be driven at speeds above 16 km/h (10 mph) to check for reappearance of its failure

DIAGNOSIS
Diagnose Code 31 by connecting the Scan tool and either driving the vehicle or rotating each wheel by hand to determine which wheel speeds are 0 KPH (0 MPH). When the faulty wheel sensors are identified proceed with the corresponding Wheel Speed = 0 trouble tree (Codes 21, 22, 23, or 24). Closely inspect the connectors in the circuitry since this is the most likely cause of a Code 31.

If both wheel speeds = 0 km/h (0 mph) check the inline Connector located behind the driver side kick panel for a bad connection or the body extension harness to the body extension harness to the rear axle harness connector for a bad connection.

DIAGNOSTIC AIDS
Before proceeding make a thorough visual inspection of the wheel speed sensor circuitry. Closely inspect the inline connector(s) since this is thee most likely area for opens or shorts.

Connect the Scan tool, spin the wheel by hand, and monitor the wheel speed. Make a comparison with other wheels.

^ Visually inspect the sensors for a loose fastener or damage.
^ Using an ohmmeter to check resistance, shake wires to locate intermittents.

Check the tightness of the female terminal grip with a spare male terminal.

When attempting to diagnose an intermittent probe, use the Scan tool (select Malfunction History from Scan tool ABS menu) to review supplemental diagnostic information. The supplemental date can be used to duplicate a problem.

Intermittents or opens suspected to be at the connectors can be detected by using a Diagnostic Service Probe. Voltage can be read on wires without disconnecting any connectors.