DTC 34

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

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

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

DTC 34 Left Rear Wheel Speed Sensor Circuit Open Or Shorted 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 the ABS relay has been turned "ON." If the EBCM/EBTCM detects an out of range voltage in either the high or low wheel speed circuits, a malfunction exists.

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

DTC Chart Test Description:
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks wheel speed sensor circuitry for proper resistance values at the EBCM/EBTCM.
2. Ensures that the wheel speed sensor circuitry is not shorted to ground.
3. Checks for a short to voltage in either the high or low wheel speed signal circuits.
4. Identifies a wheel speed sensor or circuitry that is damaged and visibly apparent.
5. Determines if wheel speed signal low is shorted to voltage.
6. Determines if wheel speed signal high is shorted to voltage.
7. Checks for open or high resistance in wheel speed signal high circuitry.
8. Checks for open or high resistance in wheel speed signal low circuitry.
9. Checks wheel speed sensor for proper resistance value.
10. Isolates short to ground in wheel speed sensor signal high to dash or body harness.
11. Isolates short to ground in wheel speed sensor signal low to dash or body harness.
12. Checks for intermittent short in rear ABS axle harness.
13. Checks for short to ground in wheel speed sensor.

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" indicator lamp is "ON" only during humid conditions (rain, snow, vehicle wash) all wheel speed sensor circuitry should be thoroughly inspected for signs of water intrusion. Use the following procedure. Spray down the 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 measuring for a short to ground in a wheel speed sensor wiring circuit, manually switch the DVM to the "Mega-Ohms" range. This will ensure a high resistance short to ground will be found. See J 39200 owners manual.

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 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.