GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Grand Am 🢒 Restraints 🢒 SIR 🢒 DTC C1236

Circuit Description

The electronic brake control module (EBCM) monitors the voltage level available for system operation. A low voltage condition prevents the system from operating properly.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1236 Low System Supply Voltage

Conditions for Running the DTC
    • The vehicle speed is greater than 8 km/h (5 mph).
    • The ignition voltage is less than 10.5 volts.
    • The system relay is commanded ON.

Conditions for Setting the DTC

One of the following conditions exists for 0.72 seconds:

    • During initialization or when the system is inactive, the system voltage is less than 10.5 volts.
    • During the system operation, the system voltage is less than 9.3 volts.

Action Taken When the DTC Sets
    • The EBCM disables the ABS for the duration of the ignition cycle.
    • The ABS indicator turns ON.
    • The DRP does not function optimally.

Conditions for Clearing the DTC
    • The condition for the DTC is no longer present and the DTC is cleared with a scan tool.
    • The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles.

Diagnostic Aids
    • Test the charging system. Refer to Diagnostic System Check - Vehicle in Vehicle DTC Information.
    • Possible causes of this DTC are the following conditions:
       - A charging system malfunction
       - An excessive battery draw
       - A weak battery
       - A faulty system ground

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Use the scan tool in order to inspect the voltage to the EBCM.

    2.

  2. Use the scan tool in order to inspect the voltage to the body control module (BCM). A low voltage value in multiple modules indicates a concern in the charging system.

    3.

  3. This step verifies that the condition is still present.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the Switched Battery Voltage parameter in antilock brake system (ABS) data list.

Does the scan tool indicate the voltage is greater than the specified value?

10.5 V

Go to Diagnostic Aids

Go to Step 3

3

With a scan tool, observe the Battery Voltage parameter in the body control module (BCM) data list.

Does the scan tool indicate the voltage is greater than the specified value?

10.5 V

Go to Step 4

Go to Diagnostic System Check - Vehicle in Vehicle DTC Information

4
  1. Turn OFF the ignition.
  2. Disconnect the electronic brake control module (EBCM) harness connector.
  3. Install the J 39700 Universal Pinout Box using the J 39700-99 Cable Adapter to the EBCM harness connector only.
  4. Test the ground circuits of the EBCM including the EBCM ground for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

 

Go to Step 7

Go to Step 5

5

  1. Reconnect the EBCM harness connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Use the scan tool in order to clear the DTCs.
  4. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 6

Go to Diagnostic Aids

6

Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming.

Did you complete the repair?

--

Go to Step 7

--

7
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK