Circuit Description
When the electronic brake control relay is activated (turned ON), voltage is supplied to the valve solenoids and pump motor. This DTC will set if the EBCM looses ground or battery voltage, or if the battery is disconnected while running.
Conditions for Running the DTC
ABS conditions are normal.
Conditions for Setting the DTC
DTC C1254 is set when a running reset occurs. A running reset occurs when the vehicle is running and functions are normal then suddenly a loss of power or ground connection occurs to the EBCM.
Action Taken When the DTC Sets
| • | ABS is disabled. |
| • | The ABS warning 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 C1254 to set are: |
| - | Running reset occurred. |
| - | Loss of EBCM ground. |
| - | Sudden drop in voltage. |
| - | Poor or loose ground connections. |
| - | Poor or loose power connections. |
| - | Battery disconnected due to corrosion or loose battery terminals. |
| - | Internal EBCM malfunction. |
| • | It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in a misdiagnosis, causing a part replacement with a reappearance of the malfunction. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step ensures that ignition positive voltage is being received by the EBCM.
-
This step ensures that battery positive voltage is being received by the EBCM.
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 | |
Does the scan tool indicate that the Ignition Voltage parameter is greater than the specified value? | 10.5 V | Go to Step 3 | Go to Step 5 | |
With the scan tool, observe the Switched Battery Voltage parameter in the ABS data list. Does the scan tool indicate that the Switched Battery Voltage parameter is greater than the specified value? | 10.5 V | Go to Step 4 | Go to Step 6 | |
4 | Test the charging system. Refer to Symptoms - Engine Electrical in Engine Electrical. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
5 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
6 |
Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 7 |
7 | Test the ground circuit of the EBCM for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 10 | Go to Step 8 |
8 | Inspect for poor connections/terminal tension at the EBCM harness connector. 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 9 |
9 | Replace the EBCM. Refer to Electronic Brake Control Module Replacement . Did you complete the replacement? | -- | Go to Step 10 | -- |
10 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
