Circuit Description
The EBCM internal relay supplies battery voltage to the pump motor. The EBCM applies the ground needed for pump motor activation. The low side of the pump motor has a feedback circuit to the EBCM microprocessor. When the pump motor is commanded off, the feedback voltage is high. When the pump motor is winding down after being commanded on and then off, the feedback voltage is low due to the back-EMF generated in the motor windings as the rotor turns. The feedback voltage then rises correspondingly as the rotor slows to a stop and the back-EMF diminishes.
Conditions for Running the DTC
| • | The ignition is ON. |
| • | The ABS bulb check is complete. |
| • | The vehicle is moving at a speed greater than 5 km/h (3 mph). |
Conditions for Setting the DTC
C0267
The EBCM microprocessor detects low feedback voltage from the pump motor 2 seconds after the pump motor is commanded off.
C0268
The EBCM microprocessor detects high feedback voltage from the pump motor within 5 milliseconds after the pump motor is commanded off.
Action Taken When the DTC Sets
| • | The ABS indicator is commanded on. |
| • | The ABS is disabled for the remainder of the ignition cycle. |
Conditions for Clearing the DTC
| • | Repair the condition(s) responsible for setting the DTC. |
| • | Use a scan tool in order to clear the DTC. |
Diagnostic Aids
Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Inspect for the following:
| • | Backed out terminals |
| • | Improper mating |
| • | Broken locks |
| • | Corrosion |
| • | Improperly formed or damaged terminals |
| • | Poor terminal-to-wiring connections |
| • | Physically damaged wiring |
| • | Wiring broken inside the insulation |
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 the ABS Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check |
2 |
Does DTC C0267 set? | -- | Go to Step 4 | Go to Step 3 |
3 | Does DTC C0268 set? | -- | Go to Step 7 | Go to Diagnostic Aids |
Does the resistance measure greater than the specified value? | 1.0 ohms | Go to Step 9 | Go to Step 5 | |
5 | Inspect for a poor connection that could cause an open circuit between the pump motor and the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 6 |
6 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
7 | Replace the EBCM and the BPMV. Refer to Electronic Brake Control Module Replacement and Brake Pressure Modulator Valve Replacement Important: Perform the Tire Size Calibration procedure. Refer to Scan Tool Diagnostics Did you complete the replacements? | -- | Go to Step 10 | -- |
8 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Important: Perform the Tire Size Calibration procedure. Refer to Scan Tool Diagnostics Did you complete the replacement? | -- | Go to Step 10 | -- |
9 | Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC set? | -- | Go to Step 2 | System OK |
