DRL module

[tgwright]

My DRL's have been inop for a year or so now, and I recently went through the troubleshooting procedure in the GM shop manual. It appears that I need a new DRL module, which is simply a circuit board. Has anyone else found that this is the reason for the DRL's to fail?

[GMMerlin]

What year?

[tgwright]

Sorry. It's a '99.

[GMMerlin]

Usually the diode is what goes bad on these..

[tgwright]

I assume you mean D203? That's what I first suspected, but I'm getting power to the DRL relay terminals which supply the voltage to the DRL's, and the relay is downstream of the diode. If the diode has failed will it still allow voltage to the relay terminals (G6)?

[Jeremy-WI]

My truck showed voltage at the relay terminal(about 9 volts) when the diode was bad, never did bother to check voltage again after diode was replaced and my DRL's worked again

[777stickman]

Originally Posted by tgwright

I assume you mean D203? That's what I first suspected, but I'm getting power to the DRL relay terminals which supply the voltage to the DRL's, and the relay is downstream of the diode. If the diode has failed will it still allow voltage to the relay terminals (G6)?

D203 is correct. When the diode fails it "usually" stops all voltage feed to the relay. Is the DRL indicator lamp in the instrument panel on with the key in the "run" position and the light switch off and the parking brake released? If is "not" on then suspect the module, light switch or parking brake switch. If it's "on" and you've determined the diode is ok, then suspect the relay. It's a cheap and easy trouble shooting replacement. Let us know............Steve

[wonder squirrel]

Bringing this thread back for a question.

How do you remove the diode assembly from under the dash? Does it require taking the dash apart? I can see the piece, but can't feel any bolts/ screws holding on

[tgwright]

On my '99 I found that the easiest thing for me to do was to simply bend down the two tabs on the mounting bracket and slide the diode out the bottom. I had to flex the bracket a little to get the diode to clear some of the structure there, but the diode slid right out. Then unplug the old, plug in the new, and slide it back into place in the bracket. Then bend the tabs back over so the new diode won't slide out.

[wonder squirrel]

Originally Posted by tgwright

On my '99 I found that the easiest thing for me to do was to simply bend down the two tabs on the mounting bracket and slide the diode out the bottom. I had to flex the bracket a little to get the diode to clear some of the structure there, but the diode slid right out. Then unplug the old, plug in the new, and slide it back into place in the bracket. Then bend the tabs back over so the new diode won't slide out.

So theres no bolts or screws holding it into place? Only the bracket? I'll have to go give it a shot and see if I can get it out that way, thanks for the help

[bigrockk]

Hello,
I know this thread is old but I was hoping someone could tell what the diode looks like.
Does it have fairly large heat sinks (fins) on it?

Thanks in advance

[tgwright]

The diode is roughly the size and shape of a pack of cigarettes and is located to the right of the steering column just under the dash. I found it necessary to remove the lower dash to access the diode.

[tgwright]

And yes, it does have heat sink fins around it. In fact it is mostly fins.

[bigrockk]

Thank you for the info and a quick reply.
At least now I know I am looking at the correct component.

I can see the diode with the lower dash in place but it will have to be removed to do the replacment. I will tackle today and see how it goes.
Thanks again.

[bigrockk]

Hey I just thought I would let you know that I did get the Diode changed and the DRL'S are back to normal.
I used "tgwright's" method for replacing it and it worked great.
Thanks again!