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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC C0200 Right Front Wheel Speed Sensor Circuit
    • DTC C0205 Left Front Wheel Speed Sensor Circuit
    • DTC C0210 Right Rear Wheel Speed Sensor Circuit
    • DTC C0215 Left Rear Wheel Speed Sensor Circuit
    • DTC C1235 Right Front Wheel Speed Sensor Circuit Open
    • DTC C1236 Left Front Wheel Speed Sensor Circuit Open
    • DTC C1238 Right Rear Wheel Speed Sensor Circuit Open
    • DTC C1239 Left Rear Wheel Speed Sensor Circuit Open
    • DTC C1271 Right Front Wheel Speed Sensor Circuit Low
    • DTC C1272 Left Front Wheel Speed Sensor Circuit Low
    • DTC C1273 Right Rear Wheel Speed Sensor Circuit Low
    • DTC C1274 Left Rear Front Wheel Speed Sensor Circuit Low
    • DTC C1275 Right Front Wheel Speed Range Performance
    • DTC C1276 Left Front Wheel Speed Range Performance
    • DTC C1277 Right Rear Wheel Speed Range Performance
    • DTC C1278 Left Rear Wheel Speed Range Performance

Conditions for Running the DTC

C0200, C0205, C0210, and C0215

The ignition is in the ON position.

C1235, C1236, C1238, and C1239

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

C1271, C1272, C1273, and C1274

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

C1275, C1276, C1277, and C1278

    • The ignition is in the ON position.
    • Vehicle speed of 20 km/h (12 mph) or more

Conditions for Setting the DTC

C0200, C0205, C0210, and C0215

The EBCM detects one of the following conditions in the wheel speed sensor circuits:

    • An open
    • A short to ground
    • A short to voltage

C1235, C1236, C1238, and C1239

The EBCM detects noise in the wheel speed sensor signal for more than 5 seconds.

C1271, C1272, C1273, and C1274

The EBCM detects low output voltage of the wheel speed sensor.

C1275, C1276, C1277, and C1278

The EBCM detects a rapid change in the wheel speed which is determined to be unreasonable.

Action Taken When the DTC Sets

The following actions occur:

    • The EBCM disables the antilock brake system (ABS) for the duration of the ignition cycle.
    • The ABS indicator turns ON.

Conditions for Clearing the DTC

C0205, C0210, C0215, and C0220

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

C1235, C1236, C1238, and C1239

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

C1271, C1272, C1273, and C1274

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

C1275, C1276, C1277, and C1278

    • The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.
    • After the DTC is cleared, the ABS indicator will remain ON until the vehicle is road tested to verify the repair. Once the vehicle has been driven at a speed above 16 km/h (10 mph) for 20 seconds with no malfunctions present, the EBCM will turn OFF the ABS indicator.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • A short to ground or a short to voltage in the wheel speed sensor circuitry
    • An open or high resistance in the wheel speed sensor circuitry
    • A malfunctioning wheel speed sensor
    • A malfunctioning wheel speed sensor rotor
    • An internal EBCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections .

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests the wheel speed sensor for the proper resistance value.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Important: Interruption or loss of communication with the scan tool may occur if speed exceeds 56 km/h (35 mph).

  4. Drive the vehicle at a speed greater than the specified value for 30 seconds.

Does the scan tool indicate that this wheel speed DTC set?

45 km/h (28 mph)

Go to Step 3

Go to Diagnostic Aids

3

  1. Raise and support the vehicle. Refer to Lifting and Jacking the Vehicle .
  2. Disconnect the wheel speed sensor connector.
  3. Measure the resistance across the wheel speed sensor.

Does the resistance measure within the specified range?

Front: 920-1220 ohms @ 20°C (69°F)

Rear (FWD): Below 1450 ohms @ 20°C (69°F)

Rear (AWD): 800-120 ohms @ 20°C (69°F)

Go to Step 4

Go to Step 10

4

Measure the resistance between the wheel speed sensor terminals and ground.

Does the resistance measure greater than specified?

Greater than 10 k ohms @ 20°C (69°F)

Go to Step 5

Go to Step 10

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 .

Did you find and correct the condition?

--

Go to Step 13

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 Wiring Repairs .

Did you find and correct the condition?

--

Go to Step 13

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 .

Did you find and correct the condition?

--

Go to Step 13

Go to Step 8

8

Inspect the wheel speed sensor for damage.

Is the wheel speed sensor damaged?

--

Go to Step 10

Go to Step 9

9

Inspect the wheel speed sensor rotor for damage.

Is the wheel speed sensor rotor damaged?

--

Go to Step 11

Go to Step 12

10

Replace the wheel speed sensor. Refer to Front Wheel Speed Sensor Replacement or Rear Wheel Speed Sensor Replacement .

Did you complete the replacement?

--

Go to Step 13

--

11

Replace the wheel speed sensor rotor. Refer to Front Wheel Drive Shaft Replacement or Rear Wheel Drive Shaft Replacement or Rear Wheel Bearing and Hub Replacement .

Did you complete the replacement?

--

Go to Step 13

--

12

Replace the brake pressure modulator valve (BPMV). Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

  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