Circuit Description
The ABS relay supplies battery voltage to 6 valve solenoids. The electronic brake control module (EBCM) microprocessor applies the grounds needed to activate each solenoid. The low side of each solenoid coil has a feedback circuit to the EBCM microprocessor. When a solenoid is commanded OFF, the feedback voltage is high. When a solenoid is commanded ON, the feedback voltage is low.
DTC Descriptors
This diagnostic procedure supports the following DTCs:
| • | DTC C0265 EBCM Motor Relay Circuit |
| • | DTC C0266 EBCM Motor Relay Circuit |
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
The EBCM detects an internal malfunction.
Action Taken When the DTC Sets
C0265
If equipped, the following actions occur:
| • | The EBCM disables the DRP/ABS. |
| • | The ABS indicator turns ON. |
| • | The red Brake warning indicator turns ON. |
| • | The DIC displays the SERVICE BRAKE SYSTEM message. |
C0266
If equipped, the following actions occur:
| • | The EBCM disables the ABS. |
| • | The ABS indicator turns ON. |
| • | The DIC displays the SERVICE BRAKE SYSTEM message. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.
Diagnostic Aids
Important: Whenever the EBCM is replaced for DTC C0265 or C0266, the ABS pump motor and motor circuitry must be tested for the proper resistance. Refer to steps 7 and 8 in the diagnostic table below for testing procedures and resistance values.
C0265
Thoroughly inspect connections and circuitry that may cause an intermittent malfunction. Refer to the following:
C0266
Replace the EBCM if DTC C0266 continues to set intermittently.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step tests if the battery positive voltage circuit can supply adequate power to the system relay.
-
A shorted ABS pump motor or shorted motor circuitry may damage the contacts within the system relay. Follow this step to prevent damage to a replacement EBCM.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics Connector End View Reference: Antilock Brake System Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Does DTC C0266 set? | -- | Go to Step 7 | Go to Step 3 |
3 | Does DTC C0265 set? | -- | Go to Step 4 | Go to Diagnostic Aids |
Does the test lamp illuminate? | -- | Go to Step 6 | Go to Step 5 | |
5 | Repair the open in the battery positive voltage circuit. Refer to Circuit Testing and Wiring Repairs . Did you complete the repair? | -- | Go to Step 11 | -- |
6 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 11 | Go to Step 7 |
|
Important: It may be necessary to separate the EBCM from the brake pressure modulator valve (BPMV) to gain access to the pump motor pigtail connector. If so, refer to Electronic Brake Control Module Replacement .
Does the resistance measure within the specified range? | 0.3-1 ohms | Go to Step 8 | Go to Step 10 | |
8 | Use a DMM in order to measure the resistance between the high side of the pump motor and a good ground. Does the resistance measure less than the specified value? | 0L | Go to Step 10 | Go to Step 9 |
9 | Replace the EBCM. Refer to Control Module References for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 11 | -- |
10 |
Important: Use the scan tool in order to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure, if applicable. Replace the EBCM and the BPMV. Refer to Control Module References for replacement, setup, and programming and Brake Pressure Modulator Valve Replacement . Did you complete the replacements? | -- | Go to Step 11 | -- |
11 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
