GM Service Manual Online
For 1990-2009 cars only

Object Number: 307959  Size: MF
ABS Components
Antilock Brake System Schematics
Handling Electrostatic Discharge Sensitive Parts Notice

Circuit Description

As a toothed ring passes by the wheel speed sensor, changes in the electromagnetic field cause the wheel speed sensor to produce a AC voltage signal. The frequency of the sinusoidal (AC) voltage signal is proportional to the wheel speed. The amplitude of the AC voltage signal is directly related to wheel speed and the proximity of the wheel speed sensor to the toothed ring. The proximity of the wheel speed sensor to the toothed ring is also referred to as the air gap.

Conditions for Setting the DTC

DTC C1232 can set anytime after initialization.

A malfunction exists if either of the left front wheel speed sensor circuits are open or shorted to voltage or ground.

Action Taken When the DTC Sets

    • A malfunction DTC stores.
    • The ABS/ETS disables.
    • The amber ABS/ETS warning indicators turn on.

Conditions for Clearing the DTC

    • The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used.
    • 100 drive cycles pass with no DTCs detected.

Diagnostic Aids

Many conditions may cause an intermittent malfunction. Proper use of the scan tool enhanced diagnostic function can be used in order to measure the frequency of the fault. Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:

    • Backed out terminals
    • Improper mating
    • Improperly formed or damaged terminals
    • Poor terminal-to-wiring connections
    • Rubbed-through wire insulation
    • A broken wire inside the insulation

If the customer's comments reflect that the amber ABS warning indicator is on only during moist environmental changes (rain, snow, vehicle wash), inspect all the wheel speed sensor circuitry 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 five percent saltwater solution.
  2. Add two teaspoons of salt to twelve ounces of water to make a five percent saltwater solution.

  3. Test drive the vehicle over various road surfaces (bumps, turns, etc.) above 24 km/h (15 mph) for at least 30 seconds.
  4. If the DTC returns, replace the suspected harness.

Difficulty may occur when trying to locate intermittent malfunctions in the wheel speed sensor. Do not disturb any of the electrical connections. Change electrical connections only when instructed to do so by a step in the diagnostic table. Changing the electrical connections at the correct time will ensure that an intermittent concern is found.

Front Wheel Speed Sensor Resistance

Resistance of the wheel speed sensor will increase with an increase in sensor temperature.

The following table contains resistance values for the front wheel speed sensors at varying temperatures for use in diagnosis. The values are approximate and should be used as a guideline for diagnosis.

Temperature (°C)

Temperature (°F)

Resistance (Ohms)

-34 to 4

-30 to 40

804 to 1066

5 to 43

41 to 110

956 to 1240

44 to 93

111 to 200

112 to 1463

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 switch to the OFF position.
  2. Make a 5 percent saltwater solution.
  3. Thoroughly spray the left front wheel speed sensor jumper harness with the saltwater solution.
  4. Disconnect the 24-way EBTCM harness connector C1.
  5. Use the J 39200 in order to measure the resistance between the 24-way EBTCM harness connector C1 terminal A5 and terminal B4.

Is the resistance within the specified range?

1020-1137 ohms at 20°C (68°F)

Go to Step 3

Go to Step 11

3

Use the J 39200 in order to measure the resistance between the 24-way EBTCM harness connector C1 terminal B4 and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 4

Go to Step 14

4

  1. Turn the ignition switch to the ON position.
  2. Do not start the engine.

  3. Use the J 39200 in order to measure the voltage between the 24-way EBTCM harness connector C1 terminal B4 and ground.

Is the voltage within the specified range?

0-1 V

Go to Step 7

Go to Step 5

5

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the left front wheel speed sensor at the left front wheel speed sensor connector.
  3. Turn the ignition switch to the ON position.
  4. Do not start the engine.

  5. Use the J 39200 in order to measure the voltage between the 24-way EBTCM harness connector C1 terminal B4 and ground

Is the voltage within the specified range?

0-1 V

Go to Step 6

Go to Step 19

6

Use the J 39200 in order to measure the voltage between the 24-way EBTCM harness connector C1 terminal A5 and ground.

Is the voltage within the specified range?

0-1 V

Go to Step 28

Go to Step 19

7

  1. Turn the ignition switch to the OFF position.
  2. Inspect the following terminals:
  3. • The 24-way EBTCM connector C1 terminal A5 and terminal  B4
    • The all of the remaining terminals of the 24-way EBTCM connector C1
  4. Inspect the above terminals for the following conditions:
  5. • Terminal damage
    • Poor terminal contact
    • Terminal corrosion
    • Damage, terminal corrosion, and poor terminal contact may cause an open circuit, a short to voltage, or a short to ground.

Are there signs of poor terminal contact, terminal corrosion, or damaged terminals?

--

Go to Step 24

Go to Step 8

8

Inspect the wiring of CKT 873 and CKT 830 for signs of wire damage.

Wire damage may cause the following conditions in CKT 873 and CKT 830:

    • An open circuit
    • A short to voltage
    • A short to ground

Are there signs of damaged wiring?

--

Go to Step 20

Go to Step 9

9

Inspect the harness connectors of CKT 873 and CKT 830 for signs of wire damage.

Wire damage may cause the following conditions in CKT 873 and CKT 830:

    • An open circuit
    • A short to voltage
    • A short to ground

Are there signs of damaged connectors?

--

Go to Step 21

Go to Step 10

10

  1. Reconnect the 24-way EBTCM connector C1.
  2. Reconnect the left front wheel speed sensor harness connector.
  3. Install a scan tool.
  4. Test drive the vehicle at a speed above 24 km/h (15 mph) for at least 30 seconds.
  5. Use the scan tool in order to read the DTCs.

Does DTC C1232 set as a current DTC?

--

Go to Step 27

Go to Step 28

11

  1. Disconnect the left front wheel speed sensor directly at the left front wheel speed sensor connector.
  2. Use the J 39200 in order to measure the resistance between the 24-way EBTCM connector C1 terminal B4 and the left front wheel speed sensor harness connector terminal B.

Is the resistance within the specified range?

0-2 ohms

Go to Step 12

Go to Step 22

12

Use the J 39200 in order to measure the resistance between the 24-way EBTCM connector C1 terminal A5 and the left front wheel speed sensor harness connector terminal A.

Is the resistance within the specified range?

0-2 ohms

Go to Step 13

Go to Step 22

13

Use the J 39200 in order to measure the resistance between the left front wheel speed sensor connector terminal A and the left front wheel speed sensor connector terminal B.

Is the resistance within the specified range?

1020-1137 ohms at 20°C (68°F)

Go to Step 28

Go to Step 25

14

  1. Disconnect the connector C171.
  2. Use the J 39200 in order to measure the resistance between the 24-way EBTCM connector C1 terminal B4 and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 15

Go to Step 23

15

Use the J 39200 in order to measure the resistance between the 24-way EBTCM connector C1 terminal A5 and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 16

Go to Step 23

16

  1. Thoroughly respray the left front wheel speed sensor jumper harness with the saltwater solution.
  2. Disconnect the left front wheel speed sensor directly at the left front wheel speed sensor.
  3. Use the J 39200 in order to measure the resistance between the left front wheel speed sensor jumper harness connector terminal A and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 17

Go to Step 26

17

Use the J 39200 in order to measure the resistance between the left front wheel speed sensor jumper harness connector terminal B and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 18

Go to Step 26

18

Use the J 39200 in order to measure the resistance between the left front wheel speed sensor jumper connector terminal A and ground.

Is the resistance within the specified range?

OL (Infinite)

Go to Step 28

Go to Step 26

19

Repair the short to voltage in CKT 873 or CKT 830.

If the short to voltage is found in the left front wheel speed sensor jumper harness, replace the left front wheel speed jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

20

Repair the wiring damage in CKT 873 or CKT 830.

If the wiring damage is found in the left front wheel speed sensor jumper harness, replace the left front wheel speed jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

21

Repair the connector damage in CKT 873 or CKT 830.

If the connector damage is found in the left front wheel speed sensor jumper harness, replace the left front wheel speed jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

22

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

If the open or high resistance is found in the left front wheel speed sensor jumper harness, replace the left front wheel speed jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

23

Repair the short to ground in CKT 873 or CKT 830.

If the short to ground is found in the left front wheel speed sensor jumper harness, replace the left front wheel speed jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

24

Replace all of the terminals and the connectors that exhibit signs of poor terminal contact, corrosion, or damaged terminals.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

25

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

26

Replace the left front wheel speed sensor jumper harness. Refer to Wheel Speed Sensor Jumper Harness Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

27

Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement .

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

28

Is the malfunction intermittent or not present at this time?

--

Go to Diagnostic Aids

--