GM Service Manual Online
For 1990-2009 cars only

DTC C0237 or C037 Rear Wheel Speed Signal Erratic gas


Object Number: 191474  Size: MF
ABS Components
Antilock Brake System Schematics

Circuit Description

The EBCM receives the rear wheel speed signal from the Vehicle Control Module (VCM). The rear wheel speed signal originates from the Vehicle Speed Sensor (VSS) which is connected to the VCM.

Conditions for Setting the DTC

    • EBCM seeing the rear speed signal line drop out and return. This malfunction can be caused by a malfunction in the VSS, or a fault in CKT 821, 822 or 1827.
    • The EBCM attempts to detect an erratic rear speed signal every 5 milliseconds. If the rear speed signal is missing for greater than 15 milliseconds while a vehicle speed greater than 32 km/h (20 mph) with brake applied, or 20 km/h (12 mph) with brake released a DTC C0237 will set. At this point the DTC will be condition latched. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even if the fault goes away.

Action Taken When the DTC Sets

    • The ABS indicator lamp turns on
    • The ABS disables

DTC C0237 initially sets as a condition latched code. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even if the fault goes away.

DTC C0237 is a DRP critical DTC, which means that DRP is disabled and the BRAKE indicator lamp will also light.

For a detailed explanation of malfunction responses, refer to Self-Diagnostics .

Conditions for Clearing the DTC

    • Repair the conditions responsible for setting the DTC
    • Use the Scan Tool Clear DTCs function
    • Both a Condition Latched or Ignition Latched DTC may exist momentarily, or constantly. In either of the cases, 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 a 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

Check for and clear DTCs in the VCM first.

This DTC can be set by a malfunction in the VSS, or a fault in CKT 821, 822 or 1827.

In addition, 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

Test Description

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

  1. This step uses the voltage output from the VCM to check the 1827 CKT.

  2. This step checks the 1827 CKT for proper resistance.

  3. This step checks for a short in the wiring between the ECBM and the VCM.

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. Disconnect the 10-way EBCM harness connector from the EBCM.
  3. Turn the ignition to RUN.
  4. Using a J 39200 , measure the voltage at terminal E of the 10-way EBCM harness connector.

Is the voltage measurement within the specified range?

Greater than 10 volts

Go to Step 4

Go to Step 3

3

  1. Turn the ignition to OFF.
  2. Disconnect the VCM harness connector C1 from the VCM.
  3. Using a J 39200 , measure the resistance from terminal E of the 10-way EBCM harness connector to terminal 15 of the VCM harness connector C1.

Is the resistance measurement within the specified range?

0-2ohms

Go to Step 5

Go to Step 8

4

  1. Turn the ignition to OFF.
  2. Reconnect all connectors.
  3. Turn the ignition to RUN.
  4. Using a Scan Tool , clear DTCs.
  5. Test drive the vehicle above 24 km/h (15 mph).
  6. Use a Scan Tool to read DTCs.

Did the DTC set?

--

Go to Step 6

Go to Step 7

5

Using a J 39200 , measure the resistance from terminal E of the 10-way EBCM harness connector to ground.

Is the resistance measurement within the specified range?

OL

Go to DTC P0500 Vehicle Speed Sensor (VSS) Circuit (5.0L, 5.7L), or DTC P0500 Vehicle Speed Sensor (VSS) Circuit (7.4L)

Go to  Step 9

6

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

7

Malfunction is intermittent. Inspect all connectors and harnesses for damage which may result in high resistance when all components are connected. Refer to Diagnostic Aids for more information. Perform all necessary repairs.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

8

Repair the open in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

9

Repair short to ground in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

DTC C0237 or C037 Rear Wheel Speed Signal Erratic diesel


Object Number: 363883  Size: MF
ABS Components
Antilock Brake System Schematics

Circuit Description

The EBCM receives the rear wheel speed signal from the PCM. The rear wheel speed signal originates from the Vehicle Speed Sensor (VSS) which is connected to the PCM.

Conditions for Setting the DTC

    • EBCM seeing the rear speed signal line drop out and return. This malfunction can be caused by a malfunction in the VSS, or a fault in CKT 821, 822 or 1827.
    • The EBCM attempts to detect an erratic rear speed signal every 5 milliseconds. If the rear speed signal is missing for greater than 15 milliseconds while a vehicle speed greater than 32 km/h (20 mph) with brake applied, or 20 km/h (12 mph) with brake released a DTC C0237 will set. At this point the DTC will be condition latched. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even if the fault goes away.

Action Taken When the DTC Sets

    • The ABS indicator lamp turns on
    • The ABS disables

DTC C0237 initially sets as a condition latched code. This means that the ABS system will be disabled and the ABS indicator lamp stays on as long as the condition exists. If the erratic DTC is set 3 consecutive times during the same ignition cycle, the DTC will set as an ignition latched DTC. This means that the ABS system will be disabled and the ABS indicator lamp stays on until the ignition is turned off; even if the fault goes away.

DTC C0237 is a DRP critical DTC, which means that DRP is disabled and the BRAKE indicator lamp will also light.

For a detailed explanation of malfunction responses, refer to Self-Diagnostics .

Conditions for Clearing the DTC

    • Repair the conditions responsible for setting the DTC
    • Use the Scan Tool Clear DTCs function
    • Both a Condition Latched or Ignition Latched DTC may exist momentarily, or constantly. In either of the cases, 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 a 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

Check for and clear DTCs in the PCM first.

This DTC can be set by a malfunction in the VSS, or a fault in CKT 821, 822 or 1827.

In addition, 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

Test Description

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

  1. This step uses the voltage output from the PCM to check the 1827 CKT.

  2. This step checks the 1827 CKT for proper resistance.

  3. This step checks for a short in the wiring between the ECBM and the PCM.

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. Disconnect the 10-way EBCM harness connector from the EBCM.
  3. Turn the ignition to RUN.
  4. Using a J 39200 , measure the voltage at terminal E of the 10-way EBCM harness connector.

Is the voltage measurement within the specified range?

Greater than 10 volts

Go to Step 4

Go to Step 3

3

  1. Turn the ignition to OFF.
  2. Disconnect the PCM harness connector C2 from the PCM.
  3. Using a J 39200 , measure the resistance from terminal E of the 10-way EBCM harness connector to terminal 32 of the PCM harness connector C2.

Is the resistance measurement within the specified range?

0-2ohms

Go to Step 5

Go to Step 8

4

  1. Turn the ignition to OFF.
  2. Reconnect all connectors.
  3. Turn the ignition to RUN.
  4. Using a Scan Tool , clear DTCs.
  5. Test drive the vehicle above 24 km/h (15 mph).
  6. Use a Scan Tool to read DTCs.

Did the DTC set?

--

Go to Step 6

Go to Step 7

5

Using a J 39200 , measure the resistance from terminal E of the 10-way EBCM harness connector to ground.

Is the resistance measurement within the specified range?

OL

Go to DTC P0501 Vehicle Speed Sensor (VSS) Performance (6.5L Diesel)

Go to Step 9

6

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

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

7

Malfunction is intermittent. Inspect all connectors and harnesses for damage which may result in high resistance when all components are connected. Refer to Diagnostic Aids for more information. Perform all necessary repairs.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

8

Repair the open in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--

9

Repair short to ground in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check - ABS

--