GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2003 🢒 LeSabre 🢒 DTC 🢒 DTC C1221-C1235

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 (10 mph) or more in 0.01 second. The change must occur 3 times with no more than 0.2 seconds 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

If equipped, the following actions occur:

    • The EBCM disables the ABS/TCS/VSES for the duration of the ignition cycle.
    • The EBCM temporarily suspends the TIM monitoring function while the DTC is set.
    • The DRP does not function optimally.
    • The ABS indicator turns ON.
    • The Traction Off indicator turns ON.
    • The 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 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 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 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:

  1. 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.
  2. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 40 km/h (25 mph) for at least 30 seconds.
  3. If the DTC returns, replace the suspected wheel speed sensor or repair the wheel speed sensor wiring.
  4. Rinse the area thoroughly when completed.

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

1

Did you perform the ABS Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Install a scan tool.
  2. Turn ON the ignition.
  3. Set up the scan tool snap shot feature to trigger for this DTC.
  4. Drive the vehicle at a speed greater than the specified value.

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

8 km/h (5 mph)

Go to Step 3

Go to Diagnostic Aids

3

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

Does the resistance measure within the specified range?

850-1350 ohms

Go to Step 4

Go to Step 8

4

  1. Spin the wheel.
  2. Measure the AC voltage across the wheel speed sensor.

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

    Important: Removing battery voltage or ground from the EBCM will result is the following conditions:

       • Loss of the TIM learned tire inflation configuration parameters in the EBCM
       • The EBCM sets DTC C1245.
    When the diagnosis is complete, inspect the tire pressures and perform the TIM reset. Refer to Tire Pressure Monitor Procedure in Tire Pressure Monitoring.

  1. Disconnect the EBCM harness connector.
  2. Install the J 39700 Universal Pinout Box using the J 39700-300 Cable Adapter to the EBCM harness connector only.
  3. Test the wheel speed sensor circuits for the following:
    4. • An open
    • A short to ground
    • A short to voltage
    • Shorted together

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 replacement?

--

Go to Step 10

--

9

Important: Perform the setup procedure for the EBCM. An unprogrammed EBCM will result in the following conditions:

   • Inoperative or poorly functioning system operations
   • The EBCM sets DTC C1248 and DTC C1255m3.

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

Did you complete the repair?

--

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