GM Service Manual Online
For 1990-2009 cars only
Table 1: WSS Temperature vs. Sensor Resistance (S-pickup)
Table 2: WSS Temperature vs. Sensor Resistance (S-utility and T-trucks)

Object Number: 366411  Size: MF
ABS Components
Antilock Brake System Schematics

Circuit Description

The wheel speed sensor coil emits an electromagnetic field. A toothed ring on the wheel passes by the wheel speed sensor and disrupts this electromagnetic field. The disruption in the field causes the wheel speed sensor to produce a sinusoidal (AC) voltage signal. The frequency and amplitude of the sinusoidal (AC) voltage signal are proportional to the speed of the wheel. The amplitude of the wheel speed signal is also directly related to the distance between the wheel speed sensor coil and the toothed ring. This distance is referred to as the air gap.

Conditions for Setting the DTC

    • No output signal from the left front wheel speed sensor for 1.0 second
    • Excessive left front wheel speed sensor resistance for 1.0 second

Action Taken When the DTC Sets

    • The ABS indicator lamp turns on
    • The ABS disables

DTC C0225 is a Condition Latched DTC, which indicates that the above actions remain true only as long as the condition persists.

DTC C0225 is a DRP Non Critical malfunction. If any other DTC sets before this DTC is investigated and cleared, this will become a DRP Critical malfunction and the BRAKE indicator lamp will also turn on.

Conditions for Clearing the DTC

    • Repair the conditions responsible for setting the DTC.
    • Use the Scan Tool Clear DTCs function.
    • A Condition Latched DTC may exist momentarily, or constantly. In either case, the DTC will be stored in the EBCM memory until it is repaired, and/or the DTC is cleared. After the DTC is repaired and/or cleared and the ignition is turned to ON, the ABS lamp will remain lit until the EBCM completes its power-up self test. This test concludes when the vehicle has reached a speed of greater than 13 km/h (8 mph) and the wheel speed inputs have been checked by the EBCM.

Diagnostic Aids

Any of the following conditions may cause an intermittent malfunction:

    • A poor connection
    • Wire insulation that is rubbed through
    • A wire breaks inside the insulation

Thoroughly check any circuitry that is suspected of causing the intermittent complaint for the following conditions:

    • Backed out terminals
    • Improper mating
    • Broken locks
    • Improperly formed or damaged terminals
    • Poor terminal to wiring connections
    • Physical damage to the wiring harness

When inspecting a wheel speed sensor, inspect the sensor terminals and the harness connector for corrosion. If evidence of corrosion exists, then replace the wheel speed sensor. Refer to Wheel Speed Sensor Replacement .

Resistance of the wheel speed sensor will increase with an increase in sensor temperature. Refer to the following tables for temperature/resistance values.

WSS Temperature vs. Sensor Resistance (S-pickup)

°C

°F

Ohms

Temperature vs Resistance Values (Approximate)

-40 to 4

-40 to 40

3915 to 5820

5 to 43

41 to 110

4769 to 6800

44 to 93

111 to 200

5560 to 8040

94 to 150

201 to 302

6600 to 9416

WSS Temperature vs. Sensor Resistance (S-utility and T-trucks)

°C

°F

Ohms

Temperature vs Resistance Values (Approximate)

-40 to 4

-40 to 40

1089 to 1630

5 to 43

41 to 110

1337 to 1900

44 to 93

111 to 200

1560 to 2230

94 to 150

201 to 302

1850 to 2651

Test Description

The numbers below refer to the steps in the diagnostic table:

  1. This step checks the resistance of the left front wheel speed sensor circuit.

  2. This step checks for continuity in the left front wheel speed sensor harness.

  3. This step checks the resistance of the left front wheel speed sensor.

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2

  1. Turn the ignition OFF.
  2. Disconnect the 4-way EBCM harness connector.
  3. Using a J 39200 , measure the resistance between terminals D and A of the 4-way EBCM harness connector. (Refer to the WSS temperature vs. resistance tables for applicable sensor resistance values. The values in these tables are for the temperature of the sensor, not the air temperature.)

Is the resistance measurement within the specified range?

--

Go to Step 5

Go to Step 3

3

  1. Disconnect the left front wheel speed sensor harness connector from the wheel speed sensor.
  2. Using a J 36169-A connect terminals A and B of the 2-way wheel speed sensor harness connector (chassis harness side).
  3. Using a J 39200 , measure the resistance between terminals D and A of the 4-way EBCM harness connector.

Is the resistance measurement within the specified range?

0-2 ohms

Go to Step 4

Go to Step 10

4

Using a J 39200 , measure the resistance between terminals A and B of the left front wheel speed sensor connector. (Refer to the WSS temperature vs. resistance tables for applicable sensor resistance values. The values in these tables are for the temperature of the sensor, not the air temperature.)

Is the resistance measurement within the specified range?

--

Go to Step 7

Go to Step 11

5

Inspect the 4-way EBCM harness connector for poor terminal contact or corrosion.

Does damage or corrosion exist?

--

Go to Step 8

Go to Step 6

6

  1. Reconnect all connectors.
  2. Test drive the vehicle above 24 km/h (15 mph).

Does the DTC set as a current DTC?

--

Go to Step 9

Go to Step 7

7

Malfunction is intermittent.

  1. Inspect all connectors and harnesses for damage which may result in high resistance when all components are connected.
  2. Refer to Diagnostic Aids for more information.

  3. Perform all necessary repairs.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

8

Make necessary repairs to the 4-way EBCM harness connector.

Refer to Connector Repairs .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

9

Replace the EBCM.

Refer to Electronic Brake Control Module Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

10

Repair the open or high resistance in CKT 830 or CKT 873.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

11

Replace the wheel speed sensor.

Refer to Wheel Speed Sensor Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--