Antilock Braking System (ABS)

Fig. 349 Code 23: Left Rear Wheel Speed = 0 Or Is Unreasonable (Part 1 Of 4):

Fig. 349 Code 23: Left Rear Wheel Speed = 0 Or Is Unreasonable (Part 2 Of 4):

Fig. 349 Code 23: Left Rear Wheel Speed = 0 Or Is Unreasonable (Part 3 Of 4):

Fig. 349 Code 23: Left Rear Wheel Speed = 0 Or Is Unreasonable (Part 4 Of 4):

Left Rear Wheel Speed = 0 Or Unreasonable:

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 23 can be set when the vehicle is not in an ABS stop. If the left rear wheel speed is less than half the average of the other three wheels and the vehicle speed is greater than 8 km/h (5 mph), a malfunction exists.

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

DTC Chart Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step will identify circuitry that is damaged and visibly apparent.
2. Checks for proper voltages at the rear sensor harness connector.
3. Checks for a short between the wheel signal high and low circuits.
4. This test checks wheel speed sensor for proper resistance value.
5. This step ensures the wheel speed sensor is not shorted to ground.
6. This test ensures the wheel speed sensor and sensor ring generate the proper voltage.
7. Ensures malfunction was not due to physical damage of the circuitry.
8. This step checks for proper voltages at body to ABS and fuel sender harness connector.
9. Checks for proper voltages at the engine to dash harness connector.
10. Checks for a short to ground in the wheel signal circuit.
11. This checks for an open in the wheel signal high circuit.
12. Checks wheel speed circuits for short to BATTERY at engine harness.
13. Checks for an open in the wheel signal low circuit.
14. Ensures malfunction was not due to physical damage of the circuitry.

Diagnostic Aids:
An "intermittent" malfunction is most likely 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 amber warning lamp is "ON" only during moist environmental changes, (rain, snow, vehicle wash) all wheel speed sensor circuitry should be thoroughly checked for signs of water intrusion. Use the following procedure. Spray down tile suspected area with 5% salt water solution (two teaspoons of salt to 12 oz. of water). Drive vehicle above 24 km/h (15 mph) for at least 30 seconds. If DTC returns immediately, replace suspected harness.

Any circuitry, that is suspected as 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 or corrosion or water intrusion exists, replace wheel speed sensor harness.

If wheel speed sensor harness shows evidence of water intrusion, inspect wheel speed sensor for water intrusion. If water intrusion is evident, replace wheel speed sensor.