Turn Signal Problem

[davintosh]

Fixing a non-operative corner light shouldn't be this difficult...

Last weekend I noticed the left turn signal was blinking far too rapidly, so I figured a lamp was out. Sure enough, the front-left lamp was not working in both blinker and running light modes. Figuring it was a bad lamp, I removed the headlamp assembly to get at the lamp, but doggone if the filaments in the lamp don't look ok (but I can't check it because my multimeter is on the blink.) I picked up a two-pack of replacement bulbs, but when pop it in, it still doesn't work.

The lamp socket has two wires and a female socket, and since the right side is working fine, and the connector on the lamp socket is accessible without pulling the headlight assembly, I plugged in the left side socket in place of the right side socket, and it worked! I popped the original lamp back in the socket, and it worked too. Great. I guessed that meant it's either not getting any voltage/current to the left socket in either blinker or running light modes, or there is a faulty ground...

So, I plug the right turn signal back in, but now it doesn't work either. Crap. I go to the fusebox to see if maybe something is blown, and durned if I can find a fuse for the turn signals at all. So, I crack open the Bentley and read that, "The LCM contains transistor power output stages for activating exterior lights. This eliminates the need for separate lighting fuses and relays." Great, but the Bentley only has instructions on replacing lamps, and says nothing about what to do when things don't work.

I'm guessing that unplugging and plugging the turn signal socket with the parking lights on activated some kind of safety mechanism in the LCM. So the question now is, what do I do now? The Bentley sure doesn't seem to have any information on this. Is there something that can be done to reset the LCM, or does it have to happen through a diagnostic unit of some kind?

Thanks for any help you all can offer.

[davintosh]

I guess we can close this one with a great big NEVER MIND; after having the trouble described above, I left things slightly disassembled in the garage to come in & check the Bentley and write out what's posted above. Went back out just now to button things up so my wife can drive it to work tomorrow, and find that the right front corner light was working again! Cool! So just for giggles, I plugged the left side back in, turn on the lights, and guess what; it works too! So I guess I answered my own question; the system must reset itself after a time with the ignition turned off. Switching it back on just now seems to have brought it back to full function. Go figure.

[Ricky Bobby]

good to hear it was an easy fix!

[Qsilver7]

The LCM does monitor the exterior bulbs around the vehicle and runs hot & cold checks...so in essence...it does "check" itself.

LM = lamp module (aka lamp/light control module