Circuit Description
The electronic brake control module (EBCM) monitors the voltage level available for system operation. A low voltage condition prevents the system from operating properly.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C1236 Low System Supply Voltage
Conditions for Running the DTC
| • | The vehicle speed is greater than 8 km/h (5 mph). |
| • | The ignition voltage is less than 10.8 volts. |
| • | The system relay is commanded ON. |
Conditions for Setting the DTC
One of the following conditions exists for 0.72 seconds:
| • | During initialization or when the system is inactive, the system voltage is less than 10.8 volts. |
| • | During the system operation, the system voltage is less than 9.36 volts. |
Action Taken When the DTC Sets
If equipped, the following actions occur:
| • | The EBCM disables the ABS/TCS until the DTC becomes a history DTC. |
| • | The DRP does not function optimally, or with system voltage less than 8.5 volts, the EBCM disables the DRP for the duration of the ignition cycle. |
| • | The ABS indicator turns ON. |
| • | The Traction Off indicator turns ON. |
| • | The message center displays the Service Traction System message. |
Conditions for Clearing the DTC
| • | The condition for the DTC is no longer present and the DTC is cleared with a scan tool. |
| • | The electronic brake control module (EBCM) automatically clears the history DTC when a current DTC is not detected in 100 consecutive drive cycles. |
Diagnostic Aids
| • | Test the charging system. Refer to Charging System Test in Engine Electrical. |
| • | Possible causes of this DTC are the following conditions: |
| - | A charging system malfunction |
| - | An excessive battery draw |
| - | A weak battery |
| - | A faulty system ground |
Test Description
-
Use the scan tool in order to inspect the voltage to the EBCM.
-
Use the scan tool in order to inspect the voltage to the body control module. A low voltage value in multiple modules indicates a concern in the charging system.
-
Verifies that the condition is still present.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Schematic Reference: Antilock Brake System Schematics | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
Does the scan tool indicate the voltage is greater than the specified value? | 10.8 V | Go to Diagnostic Aids | Go to Step 3 | |
With a scan tool, observe the Battery Voltage parameter in the Body Control Module data list. Does the scan tool indicate the voltage is greater than the specified value? | 10.8 V | Go to Step 4 | Go to Charging System Test in Engine Electrical | |
4 |
Did you find and correct the condition? | Go to Step 7 | Go to Step 5 | |
Does the DTC reset? | -- | Go to Step 6 | Go to Diagnostic Aids | |
6 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the repair? | -- | Go to Step 7 | -- |
7 |
Does the DTC reset? | -- | Go to Step 2 | System OK |
