Exterior Lighting Systems

DETECTION CONDITION AND POSSIBLE CAUSE

22	EXTERIOR LIGHTING SYSTEMS
DESCRIPTION	Stoplamps always on. Stoplamps always off

EXTERIOR LIGHTING SYSTEMS INSPECTION

STEP	INSPECTION		ACTION
1	PRELIMINARY CHECKS Perform the following preliminary checks: Stoplamp fuse. Stoplamp switch installation. Stoplamp bulbs. Trailer tow harness and relay system (if equipped). Add on devices into brake circuit. Are all checks OK.	Yes	Go to step 2.
1		No	Service as required. Verify a symptom no longer exists.
2	CHECK LIGHTING SYSTEM Go to SYSTEM WIRING DIAGRAMS for B2500, SYSTEM WIRING DIAGRAMS for B3000, or SYSTEM WIRING DIAGRAMS for B4000 and repair as necessary. Is a fault indicated?	Yes	Repair as required.
2		No	Go to step 3.
3	CHECK THE POWERTRAIN CONTROL MODULE (PCM) Is the vehicle equipped with automatic transmission?	Yes	Go to step 4.
3		No	Verify test results. If OK See DIAGNOSTIC INDEX to repair any additional symptoms
4	PERFORM PCM QUICK TEST Are any DTCs displayed during Continuous Memory, Key ON, Engine OFF (KOEO) or Key ON, Engine Running (KOER) Self Tests?	Yes	Check for cause, See DIAGNOSTIC TROUBLE CODE NUMBERS
4		No	Go to step 5
5	Verify test results. If OK, See DIAGNOSTIC INDEX to service any additional symptoms