GM Service Manual Online
For 1990-2009 cars only

Object Number: 339856  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 from the right front wheel speed sensor for 1.0 second
    • Excessive right 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 C0221 is a Condition Latched DTC, which indicates that the above actions remain true only as long as the condition persists.

Conditions for Clearing the DTC

Repair the conditions responsible for setting the DTC.

Diagnostic Aids

Any of the following conditions may cause an intermittent malfunction:

    • A poor connection
    • Wire insulation that is rubbed through
    • A broken wire 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

If the customer says that the ABS indicator lamp is on only during humid conditions such as rain, snow, or vehicle wash, then thoroughly inspect all wheel speed sensor circuits for signs of water intrusion. Use the following procedure:

  1. Spray the suspected area with a 5 percent salt water solution (2 teaspoons of salt to 12 oz of water).
  2. Drive the vehicle above 24 km/h (15 mph) for at least 30 seconds.

If the DTC returns, replace the suspected harness.

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

Test Description

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

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

  2. This step checks the resistance of the right front wheel speed sensor wiring.

  3. This step checks the resistance of the right 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

2

  1. Turn ignition to OFF.
  2. Disconnect the 24-way EBCM harness connector.
  3. Using a J 39200 , Measure the resistance between terminals 10 and 22 of the 24-way EBCM harness connector.

Is the resistance measurement within the specified range?

1500-2500 ohms

Go to Step 5

Go to Step 3

3

  1. Disconnect the right front wheel speed sensor harness connector from the wheel speed sensor pigtail.
  2. Using a J 36169-A connect terminal A and terminal B of the 2-way wheel speed sensor harness connector (chassis harness side).
  3. Using a J 39200 measure the resistance between terminals 10 and 22 of the 24-way EBCM harness connector.

Is the resistance measurement within the specified range?

0-2 ohms

Go to Step 4

Go to Step 7

4

Using a J 39200 , measure the resistance between terminal A and terminal B of the right front wheel speed sensor pigtail.

Is the resistance measurement within the specified range?

1500-2500 ohms

Go to Step 5

Go to Step 8

5

  1. Inspect the 24-way EBCM harness connector terminals 10 and  22 for poor terminal contact or corrosion.
  2. Inspect CKT 833 and CKT 872 for damage that could result in an open circuit. Repair damage if evident.
  3. Replace the terminals if poor contact or corrosion exists.
  4. Reconnect all the connectors.
  5. Using the Scan Tool , clear all DTCs .
  6. Test drive the vehicle above 16 km/h (10 mph).

Does DTC C0221 set as a current DTC?

--

Go to Step 6

Go to Diagnostic Aids

6

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

Is the repair complete?

--

Go to Diagnostic System Check

--

7

Repair the open or high resistance in CKT 833 or CKT 872. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

8

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

Is the repair complete?

--

Go to Diagnostic System Check

--