GM Service Manual Online
For 1990-2009 cars only

Object Number: 324881  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

    • The left front wheel speed is less than 6 km/h (4 mph)
    • All other wheel speeds are greater than 13 km/h (8 mph)
    • No unexpected wheel acceleration/deceleration. Anything that keeps the left front wheel speed sensor low while the vehicle is moving above 13 km/h (8 mph).

Action Taken When the DTC Sets

    • The ABS indicator lamp turns on
    • The ABS disables

DTC C0226 is an Ignition Latched DTC, which indicates that the above actions remain true until the ignition is turned to OFF (even if the cause of the DTC is intermittent).

Conditions for Clearing the DTC

    • Repair the conditions responsible for setting the DTC
    • Use the Scan Tool Clear DTCs function

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

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% salt water solution (two 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, then 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 left front wheel speed sensor.

  2. This step checks the voltage output of the left front wheel speed sensor.

  3. This step checks for a short in the wiring between the left front wheel speed sensor circuits.

  4. This step checks for a short to ground in the left front wheel speed sensor circuits.

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 to OFF.
  2. Inspect the left front wheel speed sensor, sensor wire and the connectors for signs of damage or corrosion.
  3. Inspect the wheel speed sensor and the toothed ring for looseness paying particular attention to the toothed ring. Any deviation will affect the wheel speed sensor output signal.
  4. Inspect the 24-way EBCM harness connector and harness for signs of damage or corrosion.

Is there evidence of physical damage?

--

Go to Step 8

Go to Step 3

3

  1. Disconnect the left front wheel speed sensor harness connector from the wheel speed sensor.
  2. Using a J 39200 , measure the resistance between terminal A and terminal B of the left front wheel speed sensor pigtail connector.

Is the resistance measurement within the specified range?

1500-2500 ohms

Go to Step 4

Go to Step 9

4

  1. With the J 39200 still connected, select the A/C voltage scale.
  2. Spin the wheel by hand while observing the voltage reading.

Is the voltage measured equal to or greater than the specified value?

100 mV

Go to Step 5

Go to Step 9

5

  1. Disconnect the 24-way EBCM harness connector from the EBCM.
  2. Using a J 39200 Measure the resistance between terminal 11 and terminal 23 of the 24-way EBCM harness connector.

Is the resistance measurement equal to the specified value?

OL

Go to Step 6

Go to Step 11

6

  1. Reconnect the left front wheel speed sensor.
  2. Using a J 39200 , measure the resistance between terminal 11 of the 24-way EBCM harness connector and ground.

Is the resistance measurement equal to the specified value?

OL

Go to Step 7

Go to Step 12

7

  1. Inspect the 24-way EBCM harness connector terminals 11 and 23 for poor terminal contact or corrosion.
  2. Inspect CKT 830 and CKT 873 for damage that could result in a shorted circuit. Repair any evident damage.

    Replace the terminals if poor contact or corrosion exists.

  3. Reconnect all the connectors.
  4. Using the Scan Tool , clear all DTCs.
  5. Test drive the vehicle above 16 km/h (10 mph).

Does DTC C0226 set as a current DTC?

--

Go to Step 10

Go to Diagnostic Aids

8

Make necessary repairs.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

9

Replace the left front wheel speed sensor.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

10

Replace the EBCM.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

11

Repair the short between CKT 830 and CKT 873. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

12

Repair the short to ground in CKT 830 or CKT 873. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--