GM Service Manual Online
For 1990-2009 cars only

Circuit Description

As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce an alternating current (AC) voltage signal whose frequency is proportional to the wheel speed. The magnitude of this signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring often referred to as the air gap.

Conditions for Running the DTC

This test detects a short to battery, ground, or open in the right rear wheel speed sensor circuit.

Conditions for Setting the DTC

    • The wheel speed circuit is open or shorted to the battery or ground.
    • There is a loose connection in the wheel speed circuit.
    • The wheel speed sensor resistance is very high.
    • The electronic brake control module (EBCM) is malfunctioning.

Action Taken When the DTC Sets

This is a critical operational fault. The antilock brake system (ABS) is disabled and the ABS warning lamp is turned ON. The proportioning is operation.

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 in Wiring Systems.

Step

Action

Values

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

1

  1. Turn the ignition switch to OFF.
  2. Disconnect the EBCM harness connector from the EBCM.
  3. Use a digital voltmeter (DVM) to measure the resistance between terminals 9 and 10 of the connector on the EBCM harness.

Is the resistance within the specified value?

1.0-1.5 kohms

Go to Step 4

Go to Step 2

2

  1. Disconnect the harness from the right rear wheel speed sensor.
  2. Use a DVM to measure the resistance between terminals 1 and 2 of the right rear wheel speed sensor connector.

Is the resistance within the specified value?

1.0-1.5 kohms

Go to Step 4

Go to Step 3

3

Replace the wheel speed sensor.

Is the repair complete?

--

System OK

--

4

  1. Disconnect the connector C202.
  2. Use a DVM to measure the resistance between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Does the DVM show the specified value?

less than 1 ohms

Go to Step 6

Go to Step 5

5

Repair the high resistance between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Is the repair complete?

--

System OK

--

6

Use a DVM to measure the resistance between terminal 2 of the connector C202 and terminal 2 of the right rear wheel speed sensor harness connector.

Is the resistance within the specified value?

less than 1 ohms

Go to Step 8

Go to Step 7

7

Repair the high resistance between terminal 2 of the connector C202 and terminal 2 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

8

Use a DVM to measure the resistance between terminal 10 of the connector C202 and terminal 10 of the EBCM connector.

Does the DVM show the specified value?

less than 1 ohms

Go to Step 10

Go to Step 9

9

Repair the high resistance between terminal 10 of the connector C202 and terminal 10 of the EBCM connector.

Is the repair complete?

--

System OK

--

10

Use a DVM to measure the resistance between terminal 10 of the connector C202 and terminal 1 of the right rear wheel speed sensor harness connector.

Is the resistance within the specified value?

less than 1 ohms

Go to Step 12

Go to Step 11

11

Repair the high resistance between terminal 10 of the connector C202 and terminal 1 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

12

Use a DVM to measure the resistance between ground and terminal 9 of the EBCM connector.

Does the DVM show the specified value?

Go to Step 14

Go to Step 13

13

Repair the short to ground between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Is the repair complete?

--

System OK

--

14

Use a DVM to measure the resistance between ground and terminal 2 of the connector C202.

Does the DVM show the specified value?

Go to Step 16

Go to Step 15

15

Repair the short to ground between terminal 2 of the connector C202 and terminal 2 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

16

Use a DVM to measure the resistance between ground and terminal 10 of the EBCM connector.

Does the DVM show the specified value?

Go to Step 18

Go to Step 17

17

Repair the short to ground between terminal 10 of the connector C202 and terminal 10 of the EBCM connector.

Is the repair complete?

--

System OK

--

18

Use a DVM to measure the resistance between ground and terminal 10 of the connector C202.

Does the DVM show the specified value?

Go to Step 20

Go to Step 19

19

Repair the short to ground between terminal 10 of the connector C202 and terminal 1 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

20

  1. Turn the ignition switch to ON.
  2. Use a DVM to measure the voltage between ground and terminal 9 of the EBCM connector.

Is the voltage within the specified value?

0 V

Go to Step 22

Go to Step 21

21

Repair the short to voltage between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Is the repair complete?

--

System OK

--

22

  1. Turn the ignition switch to ON.
  2. Use a DVM to measure the voltage between ground and terminal 2 of the connector C202.

Is the voltage within the specified value?

0 V

Go to Step 24

Go to Step 23

23

Repair the short to voltage between terminal 2 of the connector C202 and terminal 2 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

24

  1. Turn the ignition switch to ON.
  2. Use a DVM to measure the voltage between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Is the voltage within the specified value?

0 V

Go to Step 26

Go to Step 25

25

Repair the short to voltage between terminal 2 of the connector C202 and terminal 9 of the EBCM connector.

Is the repair complete?

--

System OK

--

26

  1. Turn the ignition switch to ON.
  2. Use a DVM to measure the voltage between ground and terminal 10 of the connector C202.

Is the voltage within the specified value?

0 V

Go to Step 28

Go to Step 27

27

Repair the short to voltage between terminal 10 of the connector C202 and terminal 1 of the right rear wheel speed sensor harness connector.

Is the repair complete?

--

System OK

--

28

Replace the EBCM.

Is the repair complete?

--

System OK

--