C1236

DTC C1236 Low System Supply Voltage:

DTC C1236 Low System Supply Voltage 1 Of 2:

DTC C1236 Low System Supply Voltage 2 Of 2:

CIRCUIT DESCRIPTION
DTC C1236 monitors the voltage level available to the Electronic Brake Control Module (EBCM) controller. If the voltage drops below 11.2 volts, full performance of the ABS system is not guaranteed. During ABS operation, there are several current requirements that will cause battery voltage at the EBCM to drop. As a result, voltage is monitored prior to an ABS event to indicate good charging system condition. Voltage is also monitored during an ABS event when voltage may drop significantly.

CONDITIONS FOR SETTING THE DTC
DTC C1236 can set only if the vehicle's speed is greater than 5 km/h (3 mph).

A malfunction exists if the switched battery voltage is less than 11.4 volts without ABS being active or less than 8.4 volts during an ABS event.

ACTION TAKEN WHEN THE DTC SETS
^ A malfunction Diagnostic Trouble Code (DTC) stores.
^ The ABS disables.
^ 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 DTC(s) 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
The following conditions may cause an intermittent malfunction:
^ A poor connection
^ Rubbed-through wire insulation
^ A broken wire inside the insulation

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

Thoroughly inspect any circuitry that may be causing the intermittent complaint for the following conditions:
^ Backed out terminals
^ Improper mating
^ Broken locks
^ Improperly formed or damaged terminals
^ Poor terminal-to-wiring connections
^ Physical damage to the wiring harness

While performing a Voltage Load test, CKT 439 should be measured for high resistance or an open condition if it is noted that only the ignition voltage drops below acceptable voltage levels.

Ensure the starting and charging systems are in proper working order. The battery should be fully charged and in good condition before beginning the diagnostic table.

Important: Zero the J 39200 test leads before making any resistance measurements. Refer to the J 39200 user's manual.