DTC A033: RF Speed Sensor Circuit Open/Short to Ground/Battery
DIAGNOSTIC TROUBLE CODE (DTC) A033 RIGHT FRONT SPEED SENSOR CIRCUIT OPEN OR SHORTED TO GROUND OR 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 the 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.
Diagnosis
This test detects a short to battery, ground, or open in the right front wheel speed sensor circuit.
Cause(s)
- The wheel speed circuit is shorted to the battery or ground.
- There is a loose connection in the wheel speed circuit.
- The wheel speed sensor resistance is very high.
- The Electronic Brake Control Module (EBCM) is malfunctioning.
Fail Action
This is a critical operational fault. The Antilock Brake System (ABS) is disabled and the ABS warning lamp is turned on. The EBCM commands a rehome to ensure that the motors are in the home position.
Test Description
The number(s) below refer to step(s) on the diagnostic table.
1. Checks for proper resistance of the wheel speed sensor coil.
2. Checks for a short to ground in the wheel speed sensor wiring.
3. Checks for a short to voltage in the wheel speed sensor wiring.
4. Ensures that the malfunction was not due to physical damage of the circuitry.
8. Checks for a short to voltage in circuit DK GRN.
10. Checks for a short to voltage in circuit BRN.
13. Checks for high resistance in circuit DK GRN.
15. Checks for high resistance in circuit BRN.
17. Verifies proper wheel speed sensor resistance.
20. Checks for a short to ground in circuit BRN.
22. Checks for a short to ground in circuit DK GRN.
24. Verifies that the 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 scan tool, as described in "Scan Tool Diagnostics". Scan Tool Diagnostics
If the customer's comments reflect that the ABS warning lamp is ON only during moist environmental changes (rain, snow, vehicle wash), inspect all wheel speed sensor circuitry thoroughly for signs or water intrusion. If the Diagnostic Trouble Code (DTC) is not current, clear the DTCs and simulate the effects of water intrusion. Use the following procedure.
1. Spray down the suspected area with a 5 percent salt water solution (10 ml (two teaspoons] of salt to 355 ml [12 fluid ounces] of water).
2. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds.
3. If the DTC returns, replace the suspected harness.
Thoroughly check any circuitry suspected of causing the intermittent complaint. Look 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.
Wheel speed sensor resistance will increase as the sensor temperature increases.
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 the wheel speed sensor harness. If replacing a wheel speed sensor harness, inspect the sensor terminals. If you find evidence of corrosion or water intrusion, replace the wheel speed sensor. Refer to "Front Wheel Speed Sensor". Wheel Speed Sensor
IMPORTANT: Wheel speed sensor intermittent malfunctions may be difficult to locate. Take care not to disturb any electrical connections before performing an indicated step of this table. That will ensure that an intermittent connection will not be corrected before the source of the malfunction is found.
DTC A033 - Right Front Speed Sensor Circuit Open or Shorted to Ground or Battery