Circuit Description
As the wheel spins, the wheel speed sensor produces an AC signal. The electronic brake control module (EBCM) uses the frequency of the AC signal to calculate the wheel speed.
Conditions for Running the DTC
C1221 through C1228
| • | DTCs C1232 through C1235 are not set. |
| • | The brake pedal is not pressed. |
| • | The ABS is not active. |
C1232 through C1235
The ignition is ON.
Conditions for Setting the DTC
C1221 through C1224
All of the following conditions exists for 2.5 seconds:
| • | The suspect wheel speed equals zero. |
| • | The other wheel speeds are greater than 8 km/h (5 mph). |
| • | The other wheel speeds are within 11 km/h (7 mph) of each other. |
C1225 through C1228
The EBCM detects a rapid variation in the wheel speed. The wheel speed changes by 16 km/h or more in 0.01 second. The change must occur 3 times with no more than 1.0 second between occurrences.
C1232 through C1235
One of the following conditions exists for 0.02 seconds:
| • | A short to voltage - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both greater than 4.25 volts. |
| • | A short to ground - the wheel speed sensor signal circuit and wheel speed sensor return circuit voltages are both less than 0.75 volts. |
| • | An open - the wheel speed sensor signal circuit voltage is greater than 4.25 volts and wheel speed sensor return circuit voltage is less than 0.75 volts. |
Action Taken When the DTC Sets
| • | The EBCM disables the ABS for the duration of the ignition cycle. |
| • | The ABS indicator turns ON. |
| • | The DRP does not function optimally unless a DTC for the other wheel speed sensor on the same axle is also set, then the EBCM disables the DRP for the duration of the ignition cycle. |
| • | When the EBCM disables DRP, the red Brake warning indicator turns ON. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
C1221 through C1224
Under the following conditions, 2 Wheel Speed Sensor Input is 0 DTCs are set:
| • | The 2 suspect wheel speeds equal zero for 20 seconds. |
| • | The other wheel speeds are greater than 16 km/h (10 mph). |
| • | The other wheel speeds are within 11 km/h (7 mph) of each other. |
Diagnose each wheel speed sensor individually.
C1225 through C1228
A possible cause of this DTC is electrical noise on the wheel speed sensor harness wiring. Electrical noise could result from the wheel speed sensor wires being routed to close to high energy ignition system components, such as spark plug wires.
C1232 through C1235
If the customer comments that the ABS indicator is ON only during moist environmental conditions: rain, snow, vehicle wash, etc., inspect the wheel speed sensor wiring for signs of water intrusion. If the DTC is not current, clear all DTCs and simulate the effects of water intrusion by using the following procedure:
- Spray the suspected area with a 5 percent saltwater solution. To create a 5 percent saltwater solution, add 2 teaspoons of salt to 8 fl oz of water (10 g of salt to 200 ml of water).
- Test drive the vehicle over various road surfaces: bumps, turns, etc., above 40 km/h (25 mph) for at least 30 seconds.
- If the DTC returns, replace the suspected wheel speed sensor or repair the wheel speed sensor wiring.
- Rinse the area thoroughly when completed.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Measures the resistance of the wheel speed sensor in order to determine if the sensor has a valid resistance value.
-
Ensures that the wheel speed sensor is generating a valid AC voltage output.
Step | Action | Value | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||||||||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | |||||||||
2 |
Does the scan tool indicate that this wheel speed DTC set? | 8 km/h (5 mph) | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | ||||||||
3 |
Does the resistance measure within the specified range? | Front: 1040-1160 ohms Rear: 1044-1276 ohms | Go to Step 4 | Go to Step 8 | ||||||||
Does the AC voltage measure greater than the specified value? | 100 mV | Go to Step 5 | Go to Step 8 | |||||||||
Inspect for poor connections at the harness connector of the wheel speed sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 | |||||||||
6 |
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 | ||||||||
7 | Inspect for poor connections at the harness connector for the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 9 | ||||||||
8 | Replace the wheel speed sensor. Refer to Front Wheel Bearing and Hub Replacement in Front Suspension or Rear Wheel Bearing and Hub Replacement in Rear Suspension. Did you complete the repair? | -- | Go to Step 10 | -- | ||||||||
9 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the repair? | -- | Go to Step 10 | -- | ||||||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||
