Circuit Description (DTCs C0265/C0266)
The EBCM relay closes and vehicle battery voltage is applied to the high side of all six solenoid coils (three isolation solenoid coils and three dump solenoid coils) whenever ABS valve activity may be required. When ABS valve activity is not required, the EBCM relay opens and vehicle battery voltage is taken away from the high side of the valve solenoids. Each valve solenoid is energized when the EBCM microprocessor turns on an output driver transistor to short the low side of the solenoid coil to ground. The EBCM microprocessor monitors the state of the ground circuit with a feedback circuit on the low side of each solenoid coil. Whenever the EBCM relay is closed and a solenoid coil output driver transistor is not turned on, the feedback voltage should be high. If it is not, and the problem persists long enough, the open solenoid coil DTC will set (C0265). If the EBCM relay is not turned on, the feedback voltage should be low. If it is not, and the problem persists long enough, the shorted solenoid coil DTC will set (C0266). The relay and the six solenoid coils are located within the EBCM.
Conditions for Setting the DTC (DTC C0265)
| • | The EBCM microprocessor commands the relay on |
| • | Low voltage exists on all six solenoid driver circuits when high voltage is expected (the solenoid is not energized) |
Conditions for Setting the DTC (DTC C0266)
| • | The ABS bulb check is complete |
| • | High voltage exists on the pump motor driver circuit when all are expected to be low (the relay is not commanded on) |
Action Taken When the DTC Sets
| • | The ABS indicator lamp turns on |
| • | The ABS disables |
DTCs C0265 and C0266 are Ignition Latched DTCs, which indicates that the above actions remain true until the ignition is turned to OFF (even if the cause of the DTC is intermittent).
DTC C0265 is DRP Critical and C0266 is DRP non-Critical. DRP is only disabled and the BRAKE indicator lamp will only light when DTC C0265 is set.
Conditions for Clearing the DTC
| • | Repair the conditions responsible for setting the DTC |
| • | Use the Scan Tool Clear DTCs function |
Diagnostic Aids (DTC C0265)
DTC C0265 usually sets because of an open relay coil or non-closable relay contacts. The relay is located within the EBCM. The relay is not serviceable. If the test does not repair the DTC, then replace the EBCM.
If DTC C0265 appears with other DTCs repair the other DTCs first. Clear all DTCs. Then run three function tests with the Scan Tool . Refer to this diagnostic chart if DTC C0265 resets as current.
Diagnostic Aids (DTC C0266)
DTC C0266 usually sets when the relay contacts are stuck closed. The relay is located within the EBCM. The relay is not serviceable. If the test does not repair the DTC, then replace the EBCM.
Test Description
The numbers below refer to the steps in the diagnostic table:
-
This step determines the resistance of the power ground circuit.
-
This step determines the battery voltage available to the EBCM.
-
This step determines the resistance of the signal ground circuit.
-
This step determines the ignition voltage available to the EBCM.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Step 2 | |
2 |
Is the connector in good condition? | -- | Go to Step 3 | Go to Step 11 |
Measure the resistance between terminal A of the 2-way EBCM harness connector and the ground using a J 39200 . Is the resistance measurement within the specified range? | 0-2ohms | Go to Step 4 | Go to Step 12 | |
Measure the voltage between terminal B of the 2-way EBCM harness connector and the ground using a J 39200 . Is the voltage equal to or greater than the specified value? | 10.0 V | Go to Step 6 | Go to Step 5 | |
5 | Inspect the 60-amp ABS MaxiFuse®. Is the fuse open? | -- | Go to Step 13 | Go to Step 14 |
6 |
Is the connector in good condition? | -- | Go to Step 7 | Go to Step 15 |
Is the resistance measurement within the specified range? | 0-2ohms | Go to Step 8 | Go to Step 16 | |
Is the voltage equal to or greater than the specified value? | 10.0 V | Go to Step 10 | Go to Step 9 | |
9 | Inspect the 10-amp BRAKE fuse. Is the fuse open? | -- | Go to Step 17 | Go to Step 18 |
10 |
Does the DTC set as a current DTC? | -- | Go to Step 19 | Malfunction is intermittent. Go to Diagnostic Aids |
11 | Repair the 2-way EBCM harness connector. Is the repair complete? | -- | -- | |
12 | Repair the open or the high resistance in the CKT 2150 (power ground). Is the repair complete? | -- | -- | |
13 | Repair the short to ground in the CKT 442. Is the repair complete? | -- | -- | |
14 | Repair the open or the high resistance in the CKT 442. Is the repair complete? | -- | -- | |
15 | Repair the 16-way EBCM harness connector. Refer to Repairing Connector Terminals . Is the repair complete? | -- | -- | |
16 | Repair the open or the high resistance in the CKT 2150 (signal ground). Is the repair complete? | -- | -- | |
17 | Repair the short to ground in the CKT 441. Is the repair complete? | -- | -- | |
18 | Repair the open or the high resistance in the CKT 441. Is the repair complete? | -- | -- | |
19 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Is the repair complete? | -- | -- |
