GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Blazer - 2WD 🢒 DTC 🢒 DTC C0221-C0227 or C021

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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C0221 Right Front Wheel Speed Sensor Circuit Open
    • DTC C0222 Right Front Wheel Speed Signal Missing
    • DTC C0223 Right Front Wheel Speed Signal Erratic
    • DTC C0225 Left Front Wheel Speed Sensor Circuit Open
    • DTC C0226 Left Front Wheel Speed Signal Missing
    • DTC C0227 Left Front Wheel Speed Signal Erratic

Conditions for Running the DTC

C0221 and C0225

The ignition is ON.

C0222, C0223, C0226 and C0227

The vehicle speed is greater than 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

C0221 and C0225

The EBCM detects an open or shorted wheel speed sensor or wheel speed sensor circuit for 500 milliseconds.

C0222 and C0226

The corresponding wheel speed sensor signal is less than 6 km/h (4 mph) for 5 seconds, or 120 seconds in order to set both DTCs.

C0223 and C0227

The EBCM detects an erratic signal from the corresponding wheel speed sensor for 105 milliseconds.

Action Taken When the DTC Sets

C0221, C0225

If equipped, the following actions occur:

    • The EBCM disables the ABS/TCS.
    • The ABS indicator turns ON.
    • The TRACTION OFF indicator turns ON.

C0222, C0223, C0226, and C0227

If equipped, the following actions occur:

    • The EBCM disables the ABS/TCS and may disable dynamic rear proportion (DRP).
    • The ABS indicator turns ON.
    • The TRACTION OFF indicator turns ON.
    • The red Brake warning indicator may turn ON.

Conditions for Clearing the DTC
    • Repair the condition responsible for setting the DTC.
    • Use a scan tool in order to clear the DTC.
    • 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 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 C0223, C0227 or C0229 even if the system is functioning normally.

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

If the customer's concern is that the ABS indicator is on only during humid conditions such as rain, snow or vehicle wash, thoroughly inspect the wheel speed sensor circuits for signs of water intrusion. Use the following procedure in order to help isolate the problem area:

  1. Spray the suspected area with a 5 percent salt water solution.
  2. Drive the vehicle at a speed greater than 19 km/h (12 mph) for at least 30 seconds.

Repair or replace the suspect harness if the DTC sets.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Measure the resistance of the wheel speed sensor in order to determine if the sensor has a valid resistance value.

    2.

  2. Ensures that the wheel speed sensor is generating a valid AC voltage output.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

Important: If DTC C0229 is set, diagnose DTC C0229 before diagnosing any other wheel speed sensor DTCs.

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2
  1. Use a scan tool in order to clear the DTCs.
  2. Operate the vehicle at a speed greater than the specified value.

Does the DTC set?

19 km/h (12 mph)

Go to Step 3

Go to Diagnostic Aids

3

  1. Turn OFF the ignition.
  2. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  3. Disconnect the wheel speed sensor connector.
  4. Use a DMM in order to measure the resistance across the wheel speed sensor.

Does the resistance measure within the specified range?

700-10,000 ohms

Go to Step 4

Go to Step 8

4

  1. Spin the wheel by hand as fast as possible.
  2. Use a DMM in order to measure the AC voltage across the wheel speed sensor as the wheel spins.

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 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
  1. Disconnect the electronic brake control module (EBCM) harness connector.
  2. Test the wheel speed sensor circuits for the following:
    3. • An open
    • A short to ground
    • A short to voltage
    • Shorted together

Refer to Circuit Testing and to 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 Wheel Speed Sensor Replacement .

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

Does the DTC reset?

--

Go to Step 2

System OK