Circuit Description
The pump motor is an integral part of the Brake Pressure Modulator Valve (BPMV), while the electronic brake control relay is integral to the EBCM. The relay supplies power to the solenoid valves and pump motor. The relay activates when the ignition is turned ON. Power is available to the solenoid valves and pump motor through the relay via the battery positive voltage circuit. The relay remains engaged until you turn OFF the ignition or a DTC which disables the ABS is set.
Conditions for Running the DTC
| • | The pump motor is commanded ON. |
| • | The switched system battery voltage is greater than 8 volts. |
Conditions for Setting the DTC
The pump motor voltage is too low. There is not enough voltage to run the pump motor during an ABS event.
Action Taken When the DTC Sets
| • | The EBCM disables the ABS for the duration of the ignition cycle. |
| • | The ABS indicator turns ON. |
Conditions for Clearing the DTC
| • | The condition responsible for setting the DTC no longer exists and the Scan Tool Clear DTCs function is used. |
| • | 100 drive cycles pass with no DTCs detected. A drive cycle consists of starting the vehicle, driving the vehicle over 16 km/h (10 mph), stopping and then turning the ignition OFF. |
Diagnostic Aids
| • | Possible causes for DTC C1218 to set are: |
| - | The pump motor ground is open. |
| - | The pump motor ground has high resistance. |
| - | The pump motor low side circuit is shorted to voltage. |
| - | Internal EBCM malfunction. |
| • | The pump motor is an integral part of the BPMV and is not serviced separately. |
| • | The system relay is an integral part of the EBCM and is not serviced separately. |
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect the wiring and connectors may result in a misdiagnosis, causing a part replacement with a reappearance of the malfunction. |
Test Description
The number below refers to the step number on the diagnostic table.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform A Diagnostic System Check-ABS? | -- | Go to Step 2 | |
2 |
Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 3 |
Does the resistance measure less than the specified value? | 2 ohms | Go to Step 4 | Go to Step 5 | |
4 |
Does the DTC reset? | -- | Go to Step 6 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
5 | Inspect for poor connections at the connector of the BPMV. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 7 |
6 | Inspect for poor connections at the harness connector of the EBCM. Did you find and correct the condition? | -- | Go to Step 9 | Go to Step 8 |
7 | Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
8 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 9 | -- |
9 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
