C0221

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 Running the DTC C0221 and C0225
Ignition switch in the RUN position.
- C0222 and C0226
- The vehicle speed is greater than 13 km/h (8 mph).
- Ignition switch in the RUN position.
- ABS not active.
- C0223 and C0227
- Ignition switch in the RUN position.
- All wheel speed sensor signals above 32 km/h (20 mph) with brake applied, or 19 km/h (12 mph) with brake released.

Conditions for Setting the DTC
C0221 and C0225
Open or short circuit in a front wheel speed sensor or sensor wiring, or anything that holds a sensor output voltage high (above 3.33 volts) for greater than 0.1 seconds, or low (below 0.039 volts) for greater than 0.5 seconds.

C0222 and C0226
The following conditions exist for greater than 5 seconds:
- Vehicle speed greater than 13 km/h (8 mph).
- One front wheel sensor speed detected less than 6 km/h (4 mph) due to:
- Wheel speed sensor signal shorted to ground.
- Wheel speed sensor signal shorted to voltage.
- Wheel speed sensor signal processing inside EBCM interrupted.
- C0223 and C0227
- Sudden loss of front wheel speed sensor signal 10 to 15 milliseconds.
- Sudden increase in front wheel speed sensor signal for 105 milliseconds (4WD only).

Action Taken When the DTC Sets
- The ABS indicator lamp turns on
- The ABS disables
Malfunction responses to DTC C0221-C0227 vary, depending on the affected subsystem.
- ABS-Condition latched
- DRP-DRP non critical
For a detailed explanation of DTC malfunction responses, refer to: Self-Diagnostics.

Conditions for Clearing the DTC
- Repair the conditions responsible for setting the DTC
- Use the Clear DTCs function on the Scan Tool
- 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 indicator lamp will remain ON 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. Refer to Wheel Speed Sensor Replacement (2WD), or Wheel Speed Sensor Replacement (4WD).

Test Description
The numbers below refer to the steps in the diagnostic chart:
[3] This step tests the wheel speed sensor for the proper resistance value.
[4] This step ensures that the wheel speed sensor generates the proper voltage.

Steps 1-2:

Steps 3-6:

Steps 7-10:

Diagnostic Chart