Infamous "'Lamp Out" warning light/chime

[MarkEagleUSA]

It seems this is a fairly common problem especially with the early Gen 3's (I've read about everything I could find regarding this problem), and it's about the last nagging issue on my 03 QC SLT. I get the "Lamp Out" warning ONLY with the parking lights on AND using either turn signal or hazard flasher. Parking lights by themselves work with no warning. Turn signals/hazards by themselves work with no warning. It's only when they're used together that the warning appears, making it difficult to narrow down where the problem actually is.

So far I've tried 2 sets of new circuit boards in the rear lights, new bulbs all around, and even brand new headlights (old ones were severely scuffed and cloudy). In addition I replaced the headlight switch (installed fog lights) and the multi-function switch (issue with variable wipers). I even checked the G104 ground since that's seems to be where all the lights are grounded according to the service manual. Checked all the sockets, connectors, and the trailer harness. Basically everything connected to the parking lights and turn signals yet I still have the 'Lamp Out".

Can anyone suggest where to look/what to do next?

Is it possible that the Front Control Module itself is bad?

Would installing a couple of load resistors like those used with LED lights help by creating more draw on the circuit?

This one has me totally stumped...

 

[Wayne M.]

Where is G104? I know there's a ground on the left frame horn just outside of where the steering gear is. Probably one out back too.

 

[MarkEagleUSA]

Where is G104?

It's on the inner fender wall above the PDC according to the service manual.

I know there's a ground on the left frame horn just outside of where the steering gear is. Probably one out back too.

I looked for one somewhere under the bed but didn't find anything.

 

[MarkEagleUSA]

Did some more troubleshooting today. Previous owner had a headlight flasher that I removed. It was connected to the park light circuit with a button connector that I replaced. Tested everything with the headlight housings out of the truck and the warning was gone. Put everything back together and the warning was still gone... for about 10 seconds. Then it returned.

This is one of the most frustrating problems I've ever encountered in a vehicle. Really not sure what to do next.

 

[Wayne M.]

Flasher? A wigwag like the cops use to alternate the hlamps side/side?
So you tested with the lamp assemblies out and got no chime? Is that right?
I haven't looked at a schematic yet, but am thinking, these might be ground controlled and monitored circuits. Therefore whatever grounds you find may not have anything to do with the actual lamp circuit. So you saying there are no grounds near the bed harness makes sense.
I think you can activate circuits via the FCM with a DRB. Good luck finding one to use. Possible Autoenginuity might.

 

[MarkEagleUSA]

Flasher? A wigwag like the cops use to alternate the hlamps side/side?

Yup.

So you tested with the lamp assemblies out and got no chime? Is that right?

Yes... had the bulb sockets out of the headlight and everything seemed to work.

I think you can activate circuits via the FCM with a DRB. Good luck finding one to use. Possible Autoenginuity might.

Nice idea but I'm not spending that kind of money for this problem.

If I have time this weekend I may remove the Front Control Module and try cleaning the contacts. If that doesn't help I think I'll order a set of OEM circuit boards for the tail lights as that seems to be a common fix for this problem.

 

[Wayne M.]

Have you tried to get a DTC out of it? If you can get a chime on command, get it to act up and then scan it. Maybe you'll get a body code?

 

[MarkEagleUSA]

Have you tried to get a DTC out of it? If you can get a chime on command, get it to act up and then scan it. Maybe you'll get a body code?

Not getting any DTC's...

 

[Wayne M.]

A few weeks ago I had the chime and intermittent lamp out going over bumps. Then it became constant. With help, I did a lamp check and found the rh brake lamp out. So I put my snap on extension between the pedal and seat, and as soon as I touched the lens, it came back on. So now it could be a bum bulb or the circuit board. I changed the bulb since I had one handy and it's been good. Maybe you have a similar thing?

 

[MarkEagleUSA]

A few weeks ago I had the chime and intermittent lamp out going over bumps. Then it became constant. With help, I did a lamp check and found the rh brake lamp out. So I put my snap on extension between the pedal and seat, and as soon as I touched the lens, it came back on. So now it could be a bum bulb or the circuit board. I changed the bulb since I had one handy and it's been good. Maybe you have a similar thing?

Every bulb is new and all are working properly. I've swapped left-to-right as well. If it's really a bulb I have no idea which one it could be.

The weird part is that when I removed that headlight flasher yesterday and put all the wiring back the way it should be, the warning stayed off for at least 30 seconds (with the front bulbs out of the housing). When I put the housing back in the warning was off for about 10 seconds and then came back.

Again, it's only with the park lamps on and use of the left/right/hazard signals that does it. I'm using Sylvania 3157LL bulbs on all 4 corners.

 

[MarkEagleUSA]

If I have time this weekend I may remove the Front Control Module and try cleaning the contacts. If that doesn't help I think I'll order a set of OEM circuit boards for the tail lights as that seems to be a common fix for this problem.

Didn't have time to pull the FCM but I did check all 4 park lamp connectors. Wires all seem to be good and the grounds don't show any excessive resistance. I've got a set of OEM tail light circuit boards due on Tuesday... if they don't help I'll go after the FCM. Not sure what else it could be at this point.

 

[MarkEagleUSA]

I've got a set of OEM tail light circuit boards due on Tuesday... if they don't help I'll go after the FCM. Not sure what else it could be at this point.

The circuit boards showed up today. Installed them with new bulbs and still have the lamp out warning. Looks like it's time for a Front Control Module...

 

[Thump]

I found that the lamp bases and/or the spade sockets for the tail light bulbs would melt a bit on my 03.5. I just took to flipping the bulbs and shaving away any melted plastic to keep that annoying ding at bay.
Often times a quick tap of the brakes shut it p for days or weeks.
I also replaced the tail light boards l, but never went as far as the FCM. Good luck.

 

[Wayne M.]

The circuit boards showed up today. Installed them with new bulbs and still have the lamp out warning. Looks like it's time for a Front Control Module...

Do you have access to any enhanced scan tools? I'd like to see if you could command on any of these circuits before getting into the FCM.

 

[MarkEagleUSA]

Do you have access to any enhanced scan tools? I'd like to see if you could command on any of these circuits before getting into the FCM.

Sadly, no access to enhanced scan tools.

 

[6speed]

Make it simple. Check all your grounds. I had the same thing. Parking lights would work great until I needed the parking/turn lights. Fixed/cleaned/tightened and all is well now.

 

[MarkEagleUSA]

Make it simple. Check all your grounds. I had the same thing. Parking lights would work great until I needed the parking/turn lights. Fixed/cleaned/tightened and all is well now.

I have already checked the grounds and everything appears ok. I may try running a direct ground from the sockets to see if that helps.

I noticed yesterday that the park lamp relay toggles on/off with the turn signal so both filaments aren't on at the same time. Makes it even stranger that it only happens using the 2 together.

 

[Tuesdak]

I replaced the front turn signal lamp holders to solve this problem on my 2003. Had intermittent contact to the bulb that would leave a black mark on the bulb's wire contact driver side. I later replaced the tail light boards for prevention. You might inspect all the bulbs looking at the contacts for similar arcing signs. I don't know if the system triggers on headlights as well, but, if they do inspect those sockets/bulbs as well.

 

[MarkEagleUSA]

The front sockets are new. The headlights do not cause the warning.

 

[MarkEagleUSA]

I replaced the front turn signal lamp holders to solve this problem on my 2003.

I'm certain this is my problem!

Pulled the headlights tonight and started wiggling the wires thinking it might be the connector. I noticed that if I held pressure against the connector/socket just right, the warning went away. Turns out the "new" sockets all behave badly. I had one "old" socket from the old headlights that I swapped in and it worked without the warning.

I just ordered 2 OEM sockets that should hopefully fix this once and for all! I'll be sure to post my results when the new sockets get installed.