Circuit Description
As the wheel spins, the wheel speed sensor (WSS) produces an AC signal. The electronic brake control module (EBCM) uses the frequency of the AC signal to calculate the wheel speed.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C1221 Left Front Wheel Speed Sensor Input Signal = 0 |
| • | DTC C1222 Right Front Wheel Speed Sensor Input Signal = 0 |
| • | DTC C1223 Left Rear Wheel Speed Sensor Input Signal = 0 |
| • | DTC C1224 Right Rear Wheel Speed Sensor Input Signal = 0 |
| • | DTC C1225 Left Front Excessive Wheel Speed Sensor Variation |
| • | DTC C1226 Right Front Excessive Wheel Speed Sensor Variation |
| • | DTC C1227 Left Rear Excessive Wheel Speed Sensor Variation |
| • | DTC C1228 Right Rear Excessive Wheel Speed Sensor Variation |
| • | DTC C1232 Left Front Wheel Speed Sensor Circuit Open or Shorted |
| • | DTC C1233 Right Front Wheel Speed Sensor Circuit Open or Shorted |
| • | DTC C1234 Left Rear Wheel Speed Sensor Circuit Open or Shorted |
| • | DTC C1235 Right Rear Wheel Speed Sensor Circuit Open or Shorted |
Conditions for Running the DTC
C1221-C1228
| • | DTCs C1232-C1235 are not set. |
| • | The brake pedal is not pressed. |
| • | The ABS is not active. |
C1232-C1235
The ignition is ON.
Conditions for Setting the DTC
C1221-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-C1228
The EBCM detects a rapid variation in the wheel speed. The wheel speed changes by 16 km/h (10 mph) or more in 0.01 second. The change must occur 3 times with no more than 0.2 seconds between occurrences.
C1232-C1235
One of the following conditions exists for 0.02 seconds:
| • | A short to voltage--The WSS signal circuit and WSS return circuit voltages are both greater than 4.25 volts. |
| • | A short to ground--The WSS signal circuit and WSS return circuit voltages are both less than 0.75 volts. |
| • | An open--The WSS signal circuit voltage is greater than 4.25 volts and WSS return circuit voltage is less than 0.75 volts. |
Action Taken When the DTC Sets
If equipped, the following actions occur:
| • | The EBCM disables the ABS/traction control system (TCS)/vehicle stability enhancement system (VSES) for the duration of the ignition cycle. |
| • | The dynamic rear proportion (DRP) does not function optimally. |
| • | The ABS indicator turns ON. |
| • | The Traction Control indicator turns ON. |
| • | The driver information center (DIC) displays the Service Stability System message. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | The EBCM automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
C1221-C1224
Under the following conditions, 2 Wheel Speed Sensor Input is 0 DTCs are set:
| • | The 2 suspect wheel speeds equal zero for 60 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 WSS individually.
C1225-C1228
A possible cause of this DTC is electrical noise on the WSS harness wiring. Electrical noise could result from the WSS wires being routed to close to high energy ignition system components, such as spark plug wires.
C1232-C1235
If the customer comments that the ABS indicator is ON only during moist environmental conditions (rain, snow, vehicle wash, etc.), inspect the WSS 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 (9.9 ml) of salt to 354 ml (12 oz) 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 WSS or repair the WSS wiring.
- Rinse the area thoroughly when completed.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step measures the resistance of the WSS in order to determine if the sensor has a valid resistance value.
-
This step ensures that the WSS is generating a valid AC voltage output.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||||
2 |
Does the scan tool indicate that this wheel speed DTC set? | 8 km/h (5 mph) | Go to Step 3 | Go to Diagnostic Aids | ||||||||
Does the resistance measure within the specified range? | 850-1350 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 | |||||||||
5 | Inspect for poor connections at the harness connector of the WSS. 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 WSS. Refer to the appropriate procedure:
Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||
9 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 10 | -- | ||||||||
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK | ||||||||
