GM Service Manual Online
For 1990-2009 cars only

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

    • The ignition is ON.
    • All of the wheel speed sensor signals are above 32 km/h (20 mph) when the brake is applied or 19 km/h (12 mph) when the brake is released.

Conditions for Setting the DTC

Either of the following conditions will set DTC C0229:

    • A sudden loss of both of the front wheel speed sensor signals is detected for 15 milliseconds.
    • A sudden increase is detected in both of the front wheel speed sensor signals for 105 milliseconds.

Action Taken When the DTC Sets

    • The ABS, BRAKE and TRACTION OFF (if equipped with traction control) indicators are commanded on.
    • The ABS, DRP and Traction Control (if equipped) are disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

    • The condition(s) responsible for setting the DTC are no longer present.
    • A scan tool is used in order to clear the DTC.

Important: After the DTC is cleared and the ignition is ON, the ABS indicator may remain on until the EBCM completes a power-up self-test. This test concludes when the vehicle reaches a speed of greater than 13 km/h (8 mph) and the wheel speeds are verified by the EBCM.

Diagnostic Aids

Operating the vehicle on extremely rough terrain can set DTC C0229 even if the system is functioning properly.

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions and Poor Connections , Wiring Repairs and Connector Repairs in Wiring Systems.

Step

Action

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check

2

  1. Use the scan tool in order to clear the DTC(s).
  2. Operate the vehicle under the conditions for running the DTC as specified in the supporting text.

Does the DTC set?

Go to Step 3

Go to Diagnostic Aids

3

Inspect for poor connections at the harness connector of 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 5

Go to Step 4

4

Replace the EBCM. Refer to Electronic Brake Control Module Replacement .

Important: Perform the Tire Size Calibration procedure.

Did you complete the replacement?

Go to Step 5

--

5

  1. Use the scan tool in order to clear the DTC.
  2. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC set?

Go to Step 3

System OK