GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Classic 🢒 Restraints 🢒 SIR 🢒 DTC C1218

Circuit Description

The system relay is energized when the ignition is ON. The system relay supplies voltage to the solenoid valves and the pump motor. This voltage is referred to as the system voltage.

The electronic brake control module (EBCM) controls each solenoid valve by grounding the solenoid.

The EBCM controls the pump motor by grounding the control circuit. The pump serves 2 purposes:

    • Transfers brake fluid from the brake calipers to the master cylinder reservoir during pressure decrease events.
    • Transfers brake fluid from the master cylinder reservoir to the brake calipers during pressure increase events.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1218 Pump Motor Circuit Short to Voltage or Motor Ground Open

Conditions for Running the DTC
    • The pump motor is commanded ON.
    • The system voltage is greater than 8 volts.

Conditions for Setting the DTC

One of the following conditions exists for 0.16 seconds:

    • With the commanded pump motor voltage less than the system voltage, the actual pump motor voltage is 3 volts less than the commanded voltage.
    • With the commanded pump motor voltage greater than the system voltage, the actual pump motor voltage is less than 8 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

The pump motor is integral to the BPMV. The pump motor is not serviceable.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests the ability of the EBCM to control the pump motor. If the test lamp illuminates, the pump motor circuit within the EBCM is good.

Step

Action

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. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.

Does the DTC reset?

Go to Step 3

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

3
  1. Turn the ignition OFF.
  2. Remove the electronic brake control module (EBCM) from the brake pressure modulator valve (BPMV). Refer to Electronic Brake Control Module Replacement .
  3. Inspect the EBCM to BPMV connector for conditions which could cause an intermittent, such as damage, corrosion, poor terminal contact, or presence of brake fluid.

Is connector OK and cavity free of brake fluid?

Go to Step 5

Go to Step 4

4
  1. If connector corrosion or damage is evident, replace BPMV and/or EBCM as necessary.
  2. If brake fluid is present, replace both BPMV and EBCM. Refer to Brake Pressure Modulator Valve Replacement and Electronic Brake Control Module Replacement .

Did you complete the repair?

Go to Step 9

--

5

  1. Connect the EBCM harness to the EBCM with the BPMV still separated.
  2. Connect a test lamp between the pump motor circuits, internal EBCM side, using the J 35616 GM Terminal Test Kit.
  3. Turn the ignition ON.
  4. With the scan tool, perform the Automated Bleed.

Does the test lamp illuminate?

Go to Step 8

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Disconnect the EBCM connector.
  3. Connect the J 39700 100-Pin Breakout Box using the J 39700-99 Breakout Box Adapter to the EBCM harness connector only.
  4. Test both 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 9

Go to Step 7

7

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 9

--

8

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

Did you complete the repair?

Go to Step 9

--

9
  1. Use the scan tool in order to clear the DTCs.
  2. With the scan tool, perform the Automated Test.

Does the DTC reset?

Go to Step 2

System OK