GM Service Manual Online
For 1990-2009 cars only

Object Number: 191380  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. When the vehicle is not moving, the VCM will have 12 VDC present on the circuit. The EBCM checks for this voltage when the vehicle is not moving.

Conditions for Setting the DTC

EBCM not seeing the correct voltage level from the VCM at startup.

Action Taken When the DTC Sets

    • The ABS indicator lamp turns on
    • The ABS disables

DTC C0235 is a Condition Latched DTC, which indicates that the above actions are true until the condition is cleared.

Conditions for Clearing the DTC

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

Diagnostic Aids

Diagnose and repair any powertrain DTCs before dignosing DTC C0235.

This DTC can be set by a faulty EBCM or a fault in CKT 1827.

If the voltage readings are low or varying, the battery or charging system could be the cause. Check these areas before replacing any components. 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

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

Refer to DTC P0500 Vehicle Speed Sensor (VSS) Circuit

Go to Step 9

6

Replace the EBCM.

Refer to Electronic Brake Control Module Replacement .

Is the repair complete?

--

Go to Diagnostic System Check

--

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

--

8

Repair the open in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check

--

9

Repair short to ground in CKT 1827.

Is the repair complete?

--

Go to Diagnostic System Check

--