B3857

CIRCUIT DESCRIPTION
The body control module (BCM) monitors the high beam headlamp signal circuit by verifying the high beam input.

CONDITIONS FOR RUNNING THE DTC
^ Voltage supplied to the module is in the normal operating voltage range (approximately 10 - 16 volts).
^ The high beam headlamps must be ON.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to voltage, short to ground or an open in the high beam headlamp signal circuit.
^ The condition must be present for more than 3 ms.

ACTION TAKEN WHEN THE DTC SETS
^ The BCM stores DTC B3857 in memory
^ The SERVICE VEHICLE SOON telltale illuminates.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B3857 will clear if the BCM no longer detects a short to battery voltage, short to ground or an open in the high beam headlamp signal circuit.
^ A history DTC B3857 will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ A DTC B3857 will clear when commanded by a scan tool.

DIAGNOSTIC AIDS
^ If the DTC B3857 is a history DTC, the fault may be intermittent. Refer to Testing for Intermittent and Poor Connections in Diagnostic Aids.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to voltage in the high beam headlamp signal circuit.
- An intermittent short to ground in the high beam headlamp signal circuit.
- An intermittent open in the high beam headlamp signal circuit.
- An intermittent short to voltage in the BCM.

TEST DESCRIPTION

Steps 1-5:

Steps 6-7:

The numbers below refer to the step numbers on the diagnostic table.
2. Test for a short to battery positive voltage in the high beam headlamp signal circuit.
3. Test for a short to ground or an open in the high beam headlamp signal circuit.