450,000 miles and the driver said that he had the light switch on all day (Were the headlights actually on? I don't know and neither does he) It was getting dark and he noticed that the headlights weren't on. Parking lights work. Everything else works to my knowledge.

I can't find a fuse to check, but with my scanner hooked up, I can see the headlight signal switch from off to on and back to off. This means the switch is good, right?

So are there fuses? I can't find a definite wiring diagram. It seems the closest I can find is one for Export.

One diagram that I found with the headlights shows BATT A1 going into the Front Control Module of the IPM then it shows twisted circuits output to the headlights.

Am I due for a Front Control Module? Is that the thing screwed to the front of the fuse box or is that the IPM? How can I test this beyond here? I have a Snap On Solus Pro scanner. I know I don't have power at the bulbs and the bulbs have been changed.

 

No there's no fuses. Yup, asinine. Which model year? The following is based on a 2002 diagram.

Looking at the diagram I have the diagnostic port is downstream of not only the switch but also the BCM so yes, it looks like an FCM may be in your future. Just to clarify, the IPM is the combination of the PDC (fuse box) and the FCM (that silver box) bolted to it. Many still refer to the IPM as the fuse box and most understand what is being said.

Might try removing the FCM and verifying the contacts are free of corrosion - a known problem. Who knows. Maybe just disconnecting and reconnecting the FCM may help. Always disconnect the negative battery lead before disconnecting/reconnecting any module. That will also reset the PCI data bus that controls the headlights among many other systems.

Might also inspect contact 3 on connector C7 on the bottom of the PDC/IPM. It's a white/violet wire and is the data bus input to the FCM (pin 22). You could also check for 12vdc B+ power at pins 1,2,9,36 of the FCM though I would think much more than the headlights would be dead if one was missing.

 

D'oh. I forgot to mention it's a 2005. I looked at the contacts on the FCM (thank you for the clarification) and they looked fine. I didn't disconnect the battery, (oops) but I will for a bit just to see.

I have cleared codes in the modules, even though there weren't any - sometimes on VWs, you need to read the codes, then clear that module even if there weren't any then read other stuff to reset it.

I recall a 2010 Dodge Ram with a headlight out that had a code and after I cleared the code, the headlight worked. But that seemed to be a little different system maybe.

Anyway. If I have power at those points and that connection on #3 is clean, then we need a FCM. Is there any coding that will need to be done? It seems that if I buy a computer from a dealer, they always say that it needs to be coded to the rig, regardless of if it does or not.

 

HAHAHAHAHAHAH

I just went out to try the lights since I hadn't done that after I R&Rd the FCM and they work.

Maybe that was all it needed. I think I will take it for a drive. Fortunately with the condition of the roads, I will get lots of bumps and jarring to see if that changes anything.

 

Well, crap. They went out again today. I unhooked the negative cable and pulled the FCM , checked it again and plugged it back in. Hooked up the Neg cable and now they work again.

So, did the FCM cool down enough to work? Did I jiggle something in the FCM that made it work? Did having the negative cable off reset it so it would work? And how do I determine if it will continue to work? $375 for a FCM at the dealer. I have a call in to the wrecking yard to see if they have one.

If they have one, will it need to be coded or is it plug and play?

 

So I pulled it into the shop and the lights were not working. I disconnected the negative cable and hooked it to the positive for 30 seconds and the lights worked. This was without disconnecting the FCM. Is this any help?

I have not checked the wire underneath on the fuse block connector.

 

Lights have been on with me driving it and stopping and going. This sucks. Even after I put in the wrecking yard FCM, I won't know if that is the problem until the driver takes it out.

 

Sounds like a microprocessor is resetting when you disconnect the battery. That would be the BCM or FCM. Your scanner is seeing the BCM do it's job. You've eliminated the FCM. All I can see now is a poor connection somewhere is the system and I would guess entering/exiting the IPM or internal to it. Would you like the wire diagram? Send me a private message and include an email address to send it to.

 

Hmmm. I thought I replied, but maybe the system logged me out.

Anyway, You said that I eliminated the FCM. I don't think I did. This thing is erratic and I'm not even sure my testing was accurate. I think that I had left the lights on and they timed out and went off. I came out and looked and assumed that they had shut off due to this problem and tested from there.

Well, the JY FCM is in, but I guess he will have to drive it and see if it works. I can't make it fail.

 

I know you said you checked the switch, but the NHTSA did an investigation regarding "Loss of headlight illumination" on Model Year 2005 and early 2006 Chrysler Minivans. The problem description was: "Complainants allege that the headlights will not illuminate (turn on) or will extinguish (go out) after being turned on. This can occur while the vehicle is at rest, or while it is being driven."

As a result of the investigation Chrysler instituted a lifetime warranty for the affected switches, it may be worth double checking your switch.

And here a link to the NHTSA findings:
http://www-odi.nhtsa.dot.gov/acms/cs...11010-4398.PDF

Here is the relevant quote from that document:
George