I have a 1999 Century. The left side amber running light is not working when it’s daylight. The right side works fine. It seemed to be an intermittent issue that’s now apparently become permanent. Below are all the details I can provide from trying to trouble shoot the problem. I hope someone has solved the same problem.
- When you activate the left turn signal in daylight, that light flashes fine. Turn off the turn signal and it goes out and stays out.
- When you manually turn on the headlights, the amber running light comes on (That appeared to be a different wire that provide that power)
- When it gets dark enough for the automatic headlight sensor, headlights and running lights come on
- From my diagram, the wire that controls the driver side amber daytime running light is light blue.
- I did get.3 volts to the multi-meter on that wire. The drivers side that’s working is getting 12 + volts when the car is running
- I have continuity on the light blue wire all the back to the point where the harness dives under the under-hood fuse block. Chasing the issue further will become major surgery.
If it was a DRL sensor it would effect both amber daytime running lights... right?
Any ides and help would be greatly appreciated. It will not pass VA state inspection with the drivers side amber light out.
And yes... the bulb is confirmed good.
Thanks!

 

Checking power to a component is only half the job.
The other half is the ground circuit.
Brush up a little on voltage drop testing and you should find the problem.

 

Yep. That’s was part of the process. There’s ground for the socket which checked out good. The turn signal shares the same hot wire as the problematic amber running light and shares the ground at the DRL module (which I can’t find under the dash) – so I’m making the assumption that ground is good. I won’t really know that until I can confirm continuity all the way back to the DRL.

I’ve spoken with a parts guy at Buick and they don’t make a replacement and don’t list any sources for aftermarket. He didn’t have a picture or illustration that would give me a clue to what I’m looking for or where to even start looking.

I’m sure a good GM wiring diagram exists that could guide me better than the one in my Chilton’s manual.

Appreciate your thoughts.

 

I would hope that I might be able to offer some useful assistance, but I need some help too.
When you say running light do you mean front parking lamp left side or left front side marker lamp?
This takes me back a little, some vehicles had what were called "Cornering lamps". Does your vehicle have this feature up front?

If I understand your vehicle's problem correctly the left front signal lamp will work when selected, but the running ?? parking /side marker light does or does not work when it is supposed to.

 

Hey Hanky,
I apologize if I’m not being clear. Attached is a picture of my car with the light in question outlined in red. During the day, the amber light supposed to be on... and its not. The other side works correctly. At night, it works fine when the headlight comes one. It also works as the turn signal. It’s just during the day when it has an issue. The light blue wire that operates the daytime running side of the build also carries the flasher signal. That’s why I’m suspecting the DRL module... but don’t know where it is under the dash or what it looks like.

My son’s buddy is going to try and grab me a wiring diagram at work through All Data. Hopefully that will have more info than the Chilton’s wiring diagram.

Hope that helps. Appreciate any additional thoughts.

 

The Chilton’s diagram show the wire running to the DRL - light blue is the left and dark blue is the right. That’s why I”m making the assumption that it’s controlled by the DRL module. The owner’s manual explains how to operate the lights... that’s about it.

I have eliminated the bulb as an issue.

The right side works correctly... the amber light come on during daytime driving. and works as the flasher on that side.

The Chilton’s manual wiring diagram aren’t very detailed. That’s why I’m trying to get one from All Data. The Chilton’s diagram didn’t make it clear that the turn signal peer came down the same wire – I know this because in the trouble shooting process, I jumped the right side over to the left. The amber daytime running light worked fine on both side, but left and right lights both flashed when the right turn signal was applied – I can hear you laughing. Had to try it though... it’s a process... right?

I’m pretty good at finding gremlins like thus, but his has been a real head scratcher. The local Buick dealership said they didn’t have a GM manual I could look at. I think that was a nice way of asking me to open up my checkbook and bend over.

Thanks!

 

I have to apologize for not coming up with a logical answer sooner. The diagram I found was somewhat difficult to read, but going on what I can discern from the diagram,
If the light works fine with the automatic headlight sensor , but not otherwise,it appears the BCM (Body Control Module) supplies the power to those lamps in the normal positions . The automatic portion is a duplicate power path. The only way to prove this would be to verify 12 volts is coming out of the BCM from terminal "E" which also is a lt blue wire. The fact that the signal lamp works tells us the wiring all the way to the lamp is good.

I think you might be looking for a new BCM.

 

THANKS!!!! Now I know where to pick up the process. I’ll let you know what I find.
Just out of curiosity... would a faulty BCM trip a code?

 

Some malfunctions will and some don't.