Circuit Description
The EBCM applies the ground needed for pump motor activation. The low side of the pump motor has a feedback circuit to the EBCM. When the pump motor is commanded off, feedback voltage is high. When the pump motor is winding down after being commanded on and then off, 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 vehicle speed is greater than 6 km/h (4 mph). |
Conditions for Setting the DTC
C0267
The EBCM detects low feedback voltage from the pump motor 2 seconds after the pump motor is commanded off.
C0268
The EBCM detects high feedback voltage from the pump motor 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
| • | The condition(s) responsible for setting the DTC are no longer present. |
| • | A scan tool is used in order to clear the DTC. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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It is imperative that the vehicle be driven to attempt to reset the DTC. Using the scan tool to perform a function test may not produce the same result, and therefore may cause misdiagnosis of the vehicle.
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This step tests if the EBCM is capable of activating the ABS pump motor.
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A shorted ABS pump motor may damage the EBCM. It is imperative that the steps in the table be followed in order to prevent damage to a replacement EBCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Connector End View Reference: | ||||
1 | Did you perform the ABS Diagnostic System Check? | -- | Go to Step 2 | Go to Diagnostic System Check |
Does DTC C0267 set? | -- | Go to Step 6 | Go to Step 3 | |
3 | Does DTC C0268 set? | -- | Go to Step 4 | Go to Diagnostic Aids |
4 |
Does the resistance measure within the specified range? | 0.0-0.2 ohms | Go to Step 5 | Go to Step 10 |
5 | Use a DMM to measure the resistance of the ground circuit. Does the resistance measure within the specified range? | 0.0-0.2 ohms | Go to Step 7 | Go to Step 11 |
6 |
Important: On some applications, it may be necessary to separate the EBCM from the BPMV in order to perform this test. Also, DTC C0268 may set when this test is performed.
Does DTC C0267 set? | -- | Go to Step 12 | Go to Step 9 |
|
Important: On some applications, it may be necessary to separate the EBCM from the BPMV in order to perform this test. Also, DTC C0268 may set when this test is performed.
Does the test lamp illuminate and then turn OFF when the Function Test is performed? | -- | Go to Step 13 | Go to Step 8 | |
Use a DMM in order to measure the resistance across the ABS pump motor. Does the resistance measure within the specified range? | 0.3-1.0 ohms | Go to Step 12 | Go to Step 14 | |
9 | Inspect for poor connections at the pump motor pigtail connector. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 15 | Go to Step 13 |
10 | Repair the high resistance in the underhood electrical center or the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- |
11 | Repair the high resistance in the ground circuit. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 15 | -- |
12 |
Important: Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure, if applicable. Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
13 | Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement . Did you complete the replacement? | -- | Go to Step 15 | -- |
14 |
Important: Following EBCM replacement, use the scan tool perform the Tire Size Calibration procedure and the Trim Level Calibration procedure, if applicable. Replace the EBCM and the BPMV. Refer to Electronic Brake Control Module Replacement and to Brake Pressure Modulator Valve Replacement . Did you complete the replacements? | -- | Go to Step 15 | -- |
15 |
Does the DTC reset? | -- | Go to Step 3 | System OK |
