Make sure to try a working head light bulb first. You don't want to buy a new PDC which costs over $300 and have it not be the problem. Chances are the dealership will not let you return electronics. If you do buy a new PDC, compare all of the fuses and realaylocations from the old PDC to the new PDC. If there are any missing fusses or relay's on the new one then just transfer those specific ones from the old one. I had to transfer at least 3. You can also save all of the old fuses and relays from the old PDC to keep as spares.

Its actually very easy. Took me only 30 min to swap.

 

Just an update:
Installed the new PDC and TA-DA! All lighting faults disappeared. Just in time for inspection. Thanks for your help.

 

The factory default for the PDC is to have the airbag fuses in the "up" position. If you connected the PDC and the airbag light is on then just open the PDC cover and push down both fuses (obviously while negative battery terminal is disconnected).

 

I have the same FMC/ICM problem that others are having. My problem is that one of my headlights work and the other doesn't. The light that doesn't work is getting 12 volts at the plug, but the light isn't turning on. This is likely because of the weak ground.

I have replaced my FMC three times and it will work for a year and then one of the headlights will fail. This leads me to believe that I am having corrosion inside the fuse box that you can't see. People have mentioned two options on how to fix the corrosion problem in the fuse box. Option one is to replace the fuse box (expensive option) and option two is to run a seperate ground within the fuse box (cheap option). I can't figure out how to run the new ground wire though. Where does it tie into within the fuse box? Someone mentioned a relay, but which relay and to which prong? There isn't a relay for the headlights? Any help someone could give me would be very helpful. With so many people having the same issues with the FMC/ICM I thought the solution would be easier to find then it has been.

 

When you use the meter to test the 12 volts, is the negative of the meter connected to the negative wire of the headlight harness or do you connect it to the chassis of the truck? If you are getting 12 volts through the wires then the bulb is clearly the problem. If you are using the meter with the negative touching the chassis and getting 12 volts then the easiest way would to be just splice the negative wire coming for the headlight harness and connect the other end under any bolt that is connected to the chassy.

When I used the meter to test the headlight power wires, it was varying continuously between 3 and 9 volts constantly. It was all over the place. Also 3 of the 4 signal lights were not working. So my only option was to change the fuse box

 

This is all very interesting stuff and takes me back to my old electrical college days.

Personally, I would not use a modern day digital multimeter to chase these transient voltages and current around.
I'd use a quality moving coil, needle style multimeter.
This way, when the meter needle swings either to the right or left, you can easily see a transient. A digital meter cannot display this as easily or readily as a moving coil meter.
As for all the problems with the PDC. I opened one up and found corrosion, all over the place. This corrosion causes a high resistance, stopping the earth return path which the FCM uses to activate/switch on the lights etc.
Hope this helps?
Al.

 

When I measured the 12 volts, I put my digital meter between the positive and the negative on the plug. I didn't ground it to anything else. I know the ground wire on the headlight is good because the same ground wire is used for both the high and low beams. The high beam works and the low beam doesn't. This basically means that when the FCM goes to try and switch the ground it can't do it.

I pulled the other working headlight (both high and low) and got 12 volts on both high and low beam wires. So on both headlights I got the same voltage.

It just sounds like this corrosion problem. Is there a way to run another ground without tearing appart the fuse box?

 

All right. I took out my existing fuse box (after disconnecting the negative terminal on battery) and cleaned all the connections. There were something like 7 plugs that connect into the bottom of the fuse box. I took out all 7 and blew out the connections. Sprayed a little WD40 (very little) on the connections and put everything back together. I also took the FCM off the side of the box. I didn't put any WD40 on this connection. I didn't put any di-electric grease or other Silcone grease because I didn't have any and I didn't think I would actually accomplish anything.

After putting everthing back together and turning on the truck, my headlights are all now on. I think this is just a temporary and there is still the corrosion inside the fuse box. This will hopefully buy me some time before I have to shell out the $450 to get a new one. I will probably have to get one adventually, but at least I know for sure my problem is the fuse box and I don't have to drop a couple hundred for the local dealership to tell me they think it is the fuse box.

 

I am having similiar problems also but it is my park lights on the drivers side both front and back flash when turn signals are on but don't burn steady. Could problem be the same

 

Sounds like a weak ground. Since the font and back park lights don't use the same ground wire from the socket, it is likely the ground within the fuse box. Your FCM would seem to be working, or else it wouldn't ever work. It sucks there isn't a way to really know for sure the fuse box is the problem. You can always try disconnecting the battery and blowing out the plugs going into the fuse box. Worked for me. Likely a temporary fix though until the corrision within the box gets worse.