Antilock Braking System (ABS)

Code 24: Rear Wheel Speed = 0.:

DTC 24 Rear Wheel Speed = 0:

Circuit Description:
As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce a sinusoidal (AC) voltage signal whose frequency is proportional to wheel speed. The magnitude of this signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring, often referred to as the air gap.

DTC Will Set When:
DTC 24 can be set when the vehicle is not in an ABS event. If the rear wheel speed = 0 and the vehicle's reference speed is greater than 8 km/h (5 mph), a malfunction exists.

Action Taken:
A malfunction DTC is stored, ABS is disabled and the amber ABS warning lamps are turned "ON."

DTC Chart Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step identifies a wheel speed sensor or circuitry that is damaged and visibly apparent.
2. Checks to see that the wheel speed sensor coil is within proper resistance values.
3. Verifies that the wheel speed sensor can generate an appropriate output signal.
4. Verifies that the wheel speed circuitry is not shorted together.
5. Ensures that the malfunction was not due to physical damage.

Diagnostic Aids:
An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation.

The frequency of the malfunction can be checked by using the enhanced diagnostic function of the Tech 1.

If the customer's comments reflect that the ABS warning lamps are "ON" only during moist environmental changes (rain, snow, vehicle wash), all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. If DTC is not current, clear DTCs and simulate the effects of water intrusion. Use the following procedure. Spray the suspected area with a 5% salt water solution (two teaspoons of salt to 12 oz. of water). Test drive vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds. If DTC returns, replace suspected harness.

Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness.

Resistance of the wheel speed sensor will increase with an increase in sensor temperature.

When replacing a wheel speed sensor, inspect the sensor terminals and harness connector for corrosion and/or water intrusion. If evidence of corrosion or water intrusion exists, replace wheel speed sensor jumper harness. Likewise, if replacing a wheel speed sensor jumper harness, inspect sensor terminals. If evidence of corrosion or water intrusion exists, replace wheel speed sensor.