Antilock Braking System (ABS)

DTC 34 Left Rear Wheel Speed Sensor Circuit Open Or Short To Ground/Battery (Part 1 Of 3).:

DTC 34 Left Rear Wheel Speed Sensor Circuit Open Or Short To Ground/Battery (Part 2 Of 3).:

DTC 34 Left Rear Wheel Speed Sensor Circuit Open Or Short To Ground/Battery (Part 3 Of 3).:

DTC 34 Left Rear Wheel Speed Sensor Circuit Open Or Short To Ground/Battery:

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 34 can be set anytime after initialization. If either of the left rear wheel speed circuits are shorted to voltage or ground, 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. Checks to see that the wheel speed sensor is within proper resistance values.
2. Checks for short to ground in wheel speed sensor wiring.
3. Checks for short to voltage in wheel speed sensor wiring.
4. Checks for a short to voltage in CKT 884.
5. Checks for a short to voltage in CKT 885.
6. Ensures malfunction was not due to physical damage of circuitry.
7. Checks for high resistance in CKT 884.
8. Checks for high resistance in CKT 885.
9. Verifies proper wheel speed sensor resistance.
10. Checks for short to ground in CKT 884.
11. Checks for short to ground in CKT 885.
12. Checks for short to ground in wheel speed sensor jumper harness.
13. Verifies that wheel speed sensor is not internally shorted to ground.

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 lamp is "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 down 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 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 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.