'94 GMC C1500 --tail lamps/rear parking lamps not working
I just purchased a '94 C1500 and am trying to fix an issue with the rear tail lamps, which do not come on with the headlamps or parking lights (the license plate lamp also fails to come on). The brake lights operate fine, as do the turn signals, hazard lights, and reverse lights.
The first thought that came to mind was a blown fuse. When I checked the panel beneath the dash, I was surprised to see hardly any fuses in the block. The manual I have been using (Haynes manual #24065, Chev. & GMC pick-ups, '88-'98 all models, '99-'00 C/K Classic)) to diagnose the problem shows a picture of a panel very similar to this, so at present I'm assuming this is normal(?) This manual also mentions an 'underhood fuse relay center' which I haven't located.
Unable to locate a fuse (and considering that the other lights are working, which seem to run off the same fuse) I replaced the bulbs, and also the tail light circuit boards, which I've heard are prone to failure. The tail lamps are still not functioning.
I have not found any breaks in the wiring from the T connection at the rear of the truck up to the front. The ground also seems solid. Are there any other components which could have failed? Please help!
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What fuse is good ? Did you check fuse in rear fuse box ? Also did you check park lamp relay .
Park, Tail and Marker Lamps
The park, tail, and marker lamps, including the license lamps, are turned ON when the headlamp switch is placed in the PARK or HEADLAMP position, or anytime the headlights are requested. The PARK LAMPS fuse in the rear fuse block supplies battery positive voltage to the PARK LAMP relay switch contacts. The PARK LAMPS fuse in the rear fuse block also supplies battery positive voltage to the PARK LAMP relay coil. When the park lamps are turned ON, the body control module (BCM) energizes the park lamp relay. Current flow is from the PARK LAMP relay to their respective park and marker lamps and to ground. Ground is provided at G101, G102, G401, and G403.
Fuse Block - Rear
Left side of the rear compartment, behind the left rear wheel well
There is an issue, you have a dead short in the circuit, no quick fix for this. You must first get a wiring diagram of the entire circuit and then follow it until you locate the shorted wire or component.
Check fuse's #19 ,# 6 #4 check grounds 105 & 107
G107 In the left rear of the engine block next to the knock sensor. G105 In the thermostat housing
The park, tail, marker and license lamps are turned on when the headlamp switch is placed in the PARK or ON position or anytime the headlights are requested. The PK LPS fuse in the IP fuse block supplies battery positive voltage to the park lamp relay and the headlamp switch. The body control module (BCM) provides a ground, or control circuit, to the park lamp relay coil circuit during ALC operation. When the park lamps are turned on during ALC, the BCM energizes the park lamp relay. The park lamps can also be supplied battery positive voltage directly from the headlamp switch. Current flow is to the park, tail, marker and license lamps. The front park and marker lamps are grounded at G100 and G101. The rear park, tail, marker and license lamps are grounded at G400 and G401. If the headlight switch is left in the ON position, the park, tail and marker lamps will remain on until turned off or the battery runs dead.
Check the headlamp switch !
Check fuse's in the rear fuse box. LR PARK fuse #14 10A - RR PARK #17 10A -
Fuse Block - Rear Beneath the left rear seat
An the park lamp relay #30 in same rear fuse box , Do you know what a BCM - body control module is ?
The body control module (BCM) provides a ground or control circuit to the park lamp relay coil circuit. When the park lamps are turned on, the BCM energizes the park lamp relay. Current flow is from the park lamp relay to the individual park lamp circuit fuses and to their respective park, tail, marker, and license lamps. The front park and marker lamps are grounded at G107 and G103. The tail lamps are grounded at G401 and G402
I won't insult you by asking if you've changed the bulbs in the rear sockets with the proper GM-numbered bulbs (no "Made in China" junk substitutes).
Identify the tail-lamp wire from the tail-lamp sockets, and trace it back to fuse block. Truck this age, my guess is you may have rat/squirrel damage to a wire. Don't know why, but varmints love to chew wires. IF the parking lamps up front work, it isn't a fuse, is why I suggest looking for a broken wire--chances are poor that you have 2 bad lamp sockets in rear.
no (park -tail-running lights) is dash parking lamps glowing?
check the tail fuse yet?
this circuit is huge, park/tail, up to 20 lamps. are all dead>?
front park, side park, tail park and dash lamps all out.
this i the red-blk feed. all comments , USA, as lighting varies by country. (laws)
license plate light dead too????????? that too is park
there is NO RELAY.
the fuse 32 feeds the HL (head light) switch and in PARK posistion
it feeds 12vdc raw power to all 38 lamps. (side corning lamps,etc)
the license plate lamp is key, there are 2 lamps.
and both probably are not out.
so if they are good lamps and both tail lamps are good and fuse
then they must glow, if one lamp shorts as 1156 or the like love to do
then it blows the fuse. as does the trailer jack (option) .
so fuse 32 park/tail blown
or HL park switch bad, if all 20 odd lamps dead. and fuse holds.
that simple, and this cars wiring is very simple and nice.
Click on the link. I tried to get whole picture, didn't make it. This is for tail lamps. Is it the tail lamps or stop lamps, I mainly looked at the tail lamps. Do the front park lamps work? If so, but not at the rear, I think there is a wiring circuit problem? At the rear, brown wire is voltage for tail lamps. Black wire is ground. The front park lamps--rear tail lamps and tag lamp all get voltage from the same source. I need to add, if you can't click on the link, type into your address box.
Park, Tail, Marker Lamps, and License
The park, tail and marker lamps, including the license lamps, turn on when the headlamp switch is placed in either the PARK or the HEAD position, or anytime the headlamps are requested. The RT I/P #1 fuse in the RH I/P fuse block supplies battery positive voltage to both the park lamp relay switch contacts and to the park lamp relay coil circuit. The park lamp relay coil is controlled by the body control module (BCM). When the headlamp switch is placed in the PARK position, the BCM energizes the park lamp relay coil control circuit.
Current flows from the park lamp relay switch to both front and rear park lamp fuses and to their respective park/tail lamps. The front park lamps are grounded at G101. The rear park lamps are grounded at G302. The license plate lamps are a part of the rear park lamp circuit and are grounded at G302. The inadvertent power control feature prevents the park lamps from remaining on more than 10 minutes if left on. If the park lamps are turned on after the ignition switch has been turned OFF, or is in the ACCY position, they will remain on until turned off or until the battery runs dead.
Did you the REAR PARK LP fuse 15 amp in the right insturment panel fuse box.