GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Epica 🢒 DTC 🢒 DTC C0018

Circuit Description

The pump motor is contained within the brake pressure modulator valve (BPMV). The pump motor ground is supplied though terminal D of the electronic brake control module (EBCM).

Conditions for Setting the DTC

DTC C0018 can only be set with the key in the ON position, the pump motor is commanded ON, and the EBCM detected a short to power or high resistance in the pump ground circuit.

Action Taken When the DTC Sets
    • The solenoid relay opens, removing power from the pump motor and solenoids.
    • DTC C0018 is stored.
    • The antilock brake system (ABS) is disabled, ABS warning lamp turns ON.

Conditions for Clearing the DTC
    • If the conditions that set DTC C0018 are no longer present, the DTC may be cleared by using the proper scan tool.
    • The DTC that has not occurred in 100 drive cycles will be deleted from history data.

Diagnostic Aids

Typical causes of DTC C0018:

    • Poor terminal contact at terminal D
    • Terminal D ground circuit shorted to voltage
    • Terminal D ground circuit open
    • Terminal D ground circuit high resistance to ground
    • Faulty EBCM

Step

Action

Values

Yes

No

1

Did you perform the Diagnostic System Check-ABS?

--

Go to Step 2

Go to Diagnostic System Check - ABS

2
  1. Turn the ignition switch OFF.
  2. Disconnect the electronic brake control module (EBCM) harness from the EBCM.
  3. Turn the ignition switch ON.
  4. Connect a voltmeter to terminal D of the EBCM.

Does the voltage measure less than the specified value?

1 V

Go to Step 4

Go to Step 3

3

Find and repair the source of the short to voltage on the terminal D ground circuit.

Did you find and correct the condition?

--

System OK

--

4
  1. Turn the ignition switch OFF.
  2. Disconnect the negative battery cable.
  3. Verify the EBCM harness is still disconnected from the EBCM.
  4. Connect an ohmmeter to the negative battery cable and then to terminal D of the EBCM harness.

Does the resistance measure less than the specified value?

2 ohms

Go to Step 6

Go to Step 5

5

Find and repair the source of high resistance between the EBCM terminal D ground circuit and body ground.

Did you find and correct the condition?

--

System OK

--

6
  1. Follow the negative battery cable to the engine block and/or chassis ground connection and inspect for a good clean and tight connection.
  2. From terminal D of the EBCM harness follow the circuit and find the location where the circuit grounds to the chassis. Inspect for a good clean and tight connection.

Were both connections clean and tight?

--

Go to Step 8

Go to Step 7

7

Repair the poor ground connection, as necessary.

Did you complete the repair?

--

System OK

--

8
  1. Verify the EBCM is still disconnected from the EBCM.
  2. Remove the EBCM from the brake pressure modulator valve (BPMV).
  3. Inspect the EBCM to BPMV connector for conditions such as damage, corrosion, poor terminal contact, or the presence of brake fluid.

Were the terminals and connector OK, and the cavity free of brake fluid, damage and corrosion?

--

Go to Step 10

Go to Step 9

9
  1. If damage and/or corrosion are present, replace the EBCM and/or the BPMV as necessary.
  2. If brake fluid is present, replace both the EBCM and the BPMV.

Did you complete the replacement?

--

System OK

--

10

Connect an ohmmeter to terminal 1 and then terminal 2 of the BPMV.

Does the resistance measure less than the specified value?

2 ohms

Go to Step 12

Go to Step 11

11

Replace the BPMV. Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

System OK

--

12

Replace the EBCM.

Did you complete the replacement?

--

System OK

--