B2647

Diagnostic Chart:

Schematics:

CIRCUIT DESCRIPTION
The ambient light sensor senses the light level to control the automatic headlamps and parklamps. The body control module (BCM) provides a 5 volt reference signal to the light sensor through CKT 1137. The BCM receives the modified voltage from the light sensor through CKT 1138. A low voltage (under 1.5V) signals a dark condition to the BCM and vice-versa.

CONDITIONS FOR RUNNING THE DTC
The ignition switch is on.

CONDITIONS FOR SETTING THE DTC
Any of the following conditions will set this DTC:
^ CKT 1137 is open for 5 seconds.
^ CKT 1137 is shorted to ground for 5 seconds.
^ CKT 1138 is open for 5 seconds.
^ CKT 1138 is shorted to ground for 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
The headlamps and parklamps are always on with the ignition on.

CONDITIONS FOR CLEARING THE DTC
^ A current DTC B2647 will clear when the malfunction is no longer present and the ignition switch is cycled.
^ All BCM history codes clear after 00 ignition cycles (from OFF to ON) with no current codes active.

DIAGNOSTIC AIDS
^ If the DTC is a history DTC the problem may be intermittent. Perform the tests while wiggling the wiring and connectors. This may often cause the malfunction to appear.

TEST DESCRIPTION
The number(s) below refer to the step number(s) on the diagnostic table.
2. The normal operating voltage of the ambient light sensor (photocell) is 0.5-4.5 volts.
3. If the value is above 0.5 volts, with the sensor disconnected, a short to voltage exists. If the value is below 0.5 volts, a short to ground exists.