GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2004 🢒 Aveo 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0018

Circuit Description

The pump motor is contained within the brake pressure modulator valve (BPMV). The pump motor ground is supplied through terminal 15 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.
    • ABS disabled, ABS warning lamp is turned ON.

Conditions for Clearing the DTC
    • If the conditions that set the 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 cleared from the history data.

Diagnostic Aids

Typical causes of DTC C0018:

    • Poor terminal contact at terminal 15
    • Terminal 15 ground circuit shorted to voltage
    • Terminal 15 ground circuit open
    • Terminal 15 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 EBCM harness from the EBCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a voltmeter to terminal 15 of the EBCM.

Was the voltage less than the specified range?

1 V

Go to Step 4

Go to Step 3

3

Find and repair the source of the short to voltage on the terminal 15 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. The EBCM harness is still disconnected from the EBCM.
  4. Connect an ohmmeter to the negative battery cable and then to terminal 15 of the EBCM harness.

Was the resistance measured less than the specified value.

2 ohms

Go to Step 6

Go to Step 5

5

Find and repair the source high resistance between the EBCM terminal 15 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 15 of the EBCM harness follow the circuit and find the location where the circuit grounds to the chassis.
  3. Inspect for a good clean and tight connection.

Were both of the connections clean and tight?

--

Go to Step 8

Go to Step 7

7

Repair the poor ground connection, as necessary.

Did you find and correct the condition?

--

System OK

--

8
  1. EBCM harness still disconnected from the EBCM.
  2. Remove the EBCM from the 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 the 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.

Was the pump motor resistance reading less than the specified value?

2 ohms

Go to Step 12

Go to Step 11

11

Replace the brake pressure modulator valve. Refer to Brake Pressure Modulator Valve Assembly Replacement .

Did you complete the replacement?

--

System OK

--

12

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

Did you complete the replacement?

--

System OK

--