Diagnosis Of Front Parking Lamps; Diagnosis Of Front Side Marker Lamps - GMC G Service Manual

DIAGNOSIS OF FRONT PARKING LAMPS

PROBLEM
One Side Not 1.
Working.
2.
Both Sides Not 1.
Working.
2.
3.
4.
5.

DIAGNOSIS OF FRONT SIDE MARKER LAMPS

Problem
One Lamp Won't 1.
Work
2.
3.
Front or Rear Lamps 1.
Won't Work
2.
All Lamps Won't 1.
Work
2.
3.
4.
POSSIBLE CAUSE
Bulb burned out.
Open connection at the bulb socket or the
ground wire terminal.
Fuse blown.
Loose connection.
Open wiring.
Multiple bulb burnout.
Defective lamp switch.
Possible Cause
Turn signal bulb burnt out (front lamp).
Side marker bulb burnt out.
Loose connection or open in wiring.
Loose connection or open ground circuit.
Multiple bulbs burnt out.
Blown fuse.
Loose connection.
Open in wiring.
Defective lamp switch.
CHASSIS ELECTRICAL 8B-3
CORRECTION
1. Replace the bulb.
2. Jumper the bulb base socket connection to
ground. If the bulb lights, repair the open
ground circuit.
1. Replace the fuse. If the new fuse blows, re­
pair the short to ground in the brown wire
circuit between the fuse panel through the
lamp switch to the lamps.
2. Secure the connector at the lamp switch.
3. Using a test lamp, check the circuit on both
sides of the fuse. If the test bulb does not light
on either side, repair the open circuit be­
tween the fuse panel and the battery (possi­
ble open fusible link). If the test bulb lights at
the lamp switch brown wire terminal, repair
the open wiring between the lamp switch and
the lamps.
4. If the test bulb lights at the lamp socket brown
wire terminal, replace the bulb(s).
5. If the test bulb lights at the lamp switch
orange wire but not at the brown wire, re­
place the defective lamp switch.
Correction
1. Switch turn signals on. If the signal bulb does
not light, replace the bulb. (Bulb filament pro­
vides ground path for marker lamp bulb
through the dark blue or brown wires.)
2. Replace the bulb.
3. Using a test lamp, check the brown wire ter­
minal at the bulb socket. If the test bulb lights,
repair the open ground circuit. If the bulb
does not light, repair the open in the brown
wire circuit.
1. If the associated tail or park lamps do not
operate, check all the connectors in the
brown wire circuit. If the park and turn lamps
are not working, repair the open ground
connections.
2. Replace the burnt out bulbs.
1. If the park and tail lamps do not operate,
replace the blown fuse. If the new fuse blows,
check for a short to ground between the fuse
panel and the lamps.
2. Secure the connector to the lamp switch.
3. Check the tail lamp fuse with a test lamp. If
the test bulb lights, repair the open wiring
between the fuse and the light switch. If not,
repair the open wiring between the fuse and
the battery. (Possible open fusible link.)
4. Check the lamp switch with a test light. If the
test bulb lights at the orange wire but not at
the brown wire, replace the lamp switch.
GMTB-0160-2L
GMTB-0846-2L