C1236

DTC C1236 Low System Supply Voltage (Part 1 Of 2):

DTC C1236 Low System Supply Voltage (Part 2 Of 2):

Voltage Supply System Schematic:

CIRCUIT DESCRIPTION
This DTC is used to monitor the voltage level available to the EBCM controller. If the battery or ignition voltage drops below the preset voltage, full performance of the ABS system cannot be guaranteed. During ABS operation, there are several current requirements that will cause battery voltage at the EBCM to drop. Because of this, voltage is monitored prior to an ABS event to indicate good charging system condition and also during an ABS event when voltage may drop significantly.

CONDITIONS FOR SETTING THE DIAGNOSTIC TROUBLE CODE (DTC)
DTC C1236 can only be set if the vehicle's speed is greater than 5 km/h (3 mph). If the switched battery voltage or ignition voltage is less than 11.5 volts non-ABS event or the battery voltage is less than 9 volts during a ABS event, a malfunction exists.

ACTION TAKEN WHEN THE DTC SETS
A malfunction DTC is stored, ABS is disabled and the amber ABS warning indicator is fumed on. The red BRAKE warning indicator is turned on if the rear piston in the ABS brake motor pack is not in the home position.

DIAGNOSTIC AIDS
An intermittent malfunction may be caused by a poor connection, rubbed through wire insulation, or a wire that is broken inside the insulation. The frequency of the malfunction can be checked by using the enhanced diagnostic function of the scan tool, as described in Scan Tool Diagnostics in the scan tool manual. Any circuitry that is suspected of causing the intermittent complaint should be thoroughly checked for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wiring connections or physical damage to the wiring harness. While performing a voltage load test, if it is noted that only the ignition voltage drops below acceptable voltage levels, CKT 641 should be checked for high resistance or an open condition.

NOTE: J 39200 test leads must be zeroed prior to making any resistance measurements. Refer to J 39200 user's manual.