DRL module

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?

What year?

Sorry. It's a '99.

Usually the diode is what goes bad on these..

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)?

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

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

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

:naughty:

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.

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 :iceslolan

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

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.

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

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.

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!

I'm also chasing a DRL non-working situation on a 99 suburban & would appreciate help / suggestions.
The summary of my situation is:
I've found my diode is bad, but with the contacts at the Diode connector lead shorted, still can't get the DRL's to work with the relay in place. With the relay removed, I can get the DRL's to work by shorting the contacts on the module (pin 87 - which goes to the DRL/fog light fuse & pin 30 which goes to the headlights)
The parking brake relay is OK.
I've bought a new DRL relay but it doesn't change the operation. Headlights work OK, but not the DRL's. Both the old and new relays give the same resistance across the contacts (approx 80 ohms) that should pull up the DRL relay (Pins 85 & 86) when voltage is applied. I see the voltage to the relay contacts when the ignition is in the run position, so know that the wring is good, but can't figure why it's not pulling up the DRL relay. Other than measuring the resistance across the relay contacts I don't know how else to prove the relay.
My DRL lamp on the dash isn't working. It was OK when I started the process, but in my fooling around has stopped functioning. I figured I had blown it while removing & replacing the relay or making shorts across contacts, but now I'm wondering if I've done something to the DRL module itself..........(All other functions I see going thru the DRL module per the wiring diagram are working OK)While losing DRL's isn't the end of the world, I'd still like to have all systems functioning properly. Any thoughts or suggestions appreciated.


Scott

Scott: Before we get too deep into this I (we) need to know what body style you have. '99 was a "carryover'"year, old vs new body style. Old style has the DRL's working the regular low beam lamps and new style has independent DRL lamps. If you have the "old" style I maybe able to help you out.........Steve