C0221

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CIRCUIT DESCRIPTION
The wheel speed sensor coil emits an electromagnetic field. A toothed ring on the wheel passes by the wheel speed sensor and disrupts this electromagnetic field. The disruption in the field causes the wheel speed sensor to produce a sinusoidal (AC) voltage signal. The frequency and amplitude of the sinusoidal (AC) voltage signal are proportional to the speed of the wheel. The amplitude of the wheel speed signal is also directly related to the distance between the wheel speed sensor coil and the toothed ring. This distance is referred to as the air gap.

CONDITIONS FOR SETTING THE DTC
- Open or short circuit in R/F wheel speed sensor or sensor wiring
- Anything that holds the R/F wheel speed sensor output voltage high or low

ACTION TAKEN WHEN THE DTC SETS
- The ABS indicator lamp turns on
- The ABS disables

DTC C0221 is a Condition Latched DTC, which indicates that the above actions remain true only as long as the condition persists.

DTC C0221 is a DRP non critical malfunction. If any other DTC sets before this DTC is investigated and cleared, this will become a DRP Critical malfunction and the BRAKE indicator lamp will also turn on.

CONDITIONS FOR CLEARING THE DTC
- Repair the conditions responsible for setting the DTC
- Use the Scan Tool Clear DTCs function
- A Condition Latched DTC may exist momentarily, or constantly. In either case, the DTC will be stored in the EBCM memory until it is repaired, and/or the DTC is cleared. After the DTC is repaired and/or cleared and the ignition is turned to ON, the ABS lamp will remain lit until the EBCM completes its power-up self test. This test concludes when the vehicle has reached a speed of greater than 13 km/h (8 mph) and the wheel speed inputs have been checked by the EBCM.

DIAGNOSTIC AIDS
Any of the following conditions may cause an intermittent malfunction:
- A poor connection
- Wire insulation that is rubbed through
- Wire breaks inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals
- Poor terminal to wiring connections
- Physical damage to the wiring harness

If the customer says that the ABS indicator lamp is on only during humid conditions such as rain, snow, or vehicle wash, then thoroughly inspect all wheel speed sensor circuits for signs of water intrusion. Use the following procedure:
1. Spray the suspected area with a 5% salt water solution (two teaspoons of salt to 12 oz. of water)
2. Drive the vehicle above 24 km/h (15 mph) for at least 30 seconds

If the DTC returns, replace the suspected harness.

When inspecting a wheel speed sensor, inspect the sensor terminals and the harness connector for corrosion. If evidence of corrosion exists, then replace the wheel speed sensor.

WSS Temperature vs. Sensor Resistance:

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

TEST DESCRIPTION
The numbers below refer to the steps in the diagnostic table:
2. This step checks for a short to voltage in the right front wheel speed sensor circuit.
3. This step checks for the proper WSS resistance in the right front wheel speed sensor circuit.
4. This step checks the right front wheel speed sensor circuit for a short to ground.
6. Since voltage has been detected in the WSS circuit, this step isolates the WSS and checks for a short to voltage in either CKT 833 or 872.
7. Since an irregular resistance has been detected in the WSS circuit, this step checks the resistance of the right front wheel speed sensor body harness circuit which will decide between a bad WSS or a bad WSS body harness circuit.
8. Since the DVM has indicated a reading other than OL, an abnormal connection between ground and the WSS circuit exists. This step will help determine in which part of the WSS circuit that this condition exists.
9. Since steps 2, 3, and 4 did not reveal the true cause of the DTC, this step will determine if any physical damage to the harness connector may have caused the problem.