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Dodgerench
Dodgerench, ASE Certified Technician
Category: Chrysler
Satisfied Customers: 3385
Experience:  30+ years Dodge/ Chrysler exp., ASE Master with L1 certification. Driveability/ combustion specialist
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I have a 2004 town and country van. My tail lights will not

Customer Question

I have a 2004 town and country van. My tail lights will not go off. I've replaced the brake switch, checked relays and fuses and still no help. Even if I push the switch all the way in with my finger they still stay on. Initially when this happened I disconnected the battery. When I reconnected the battery the next morning everything seemed to work fine. I replaced the switch anyways. Worked fine for about 20 min then the tail lights came back on. Disconnecting the battery does nothing now. Any suggestions?
Submitted: 1 year ago.
Category: Chrysler
Customer: replied 1 year ago.
I can also shift into gear from park w/o pushing on the brake pedal and my cruise won't work, as if the car thinks I'm pushing the brake
Expert:  Dodgerench replied 1 year ago.

Goood morning, welcome to JustAnswer!. This is Ed.

I'd be interested to see if your van has a towing electrical converter for brakes and signals. They sometimes use common relays, but sometimes you'll have a converter box that's used to separate or combine signals and brakes into a single or multiple bulb network. These boxes often have diodes within them that should keep the circuits separate, but sometimes they go bad and short power into circuits that shouldn't be. In your case -- with the shift interlock and speed control symptoms -- a backfeed on the brake circuit would probably be interpreted the same as if you were actually pushing the brake.

Look first for a trailer connector at the rear of the van (in case you don't know or use such a thing). My guess is a 4-pin trailer connector would be the one more likely to be involved, but if you have a 7-pin, it still qualifies. 4-pin (U-Haul) converters are sometimes wire tied in the underbody or it might be stuffed down inside a brake lamp cavity, so you might have to do some digging. The converter will often become warm to the touch if it's flowing current, which is one of the ways you can use for diagnosis that's short of cutting wires. It'll take a little while to heat up, so plug everything in and let the lights burn for 15 minutes or more.

This is just my first guess, so let me know if we need to keep looking.

Good luck!

Ed

Customer: replied 1 year ago.
It does have a four way trailer plug with a u-haul stamp on it. They were just connected at the rear of the the vehicle under the far back kick panel. The ground was self tapped into the body and the turns an brake were just tapped into the factory wires. There was no box or anything like that. This is now disconnected.
Customer: replied 1 year ago.
Doing this did nothing for the problem. Any other suggestions?
Expert:  Dodgerench replied 1 year ago.

Thanks. Would you try completely disconnecting the brake switch for me? I've been assuming the brake lamp circuit was involved here, but it might be the signal or park lamps. If it affects only the rear lamps, it's likely to be the brake circuit, but you know how that goes. If it's a brake circuit, your center high-mount stop lamp (the one in the liftgate) should also be lit.

If the circuit remains hot, we've definitely got something leaking into the stop lamp wiring somehow. Wire color for the stop lamps is white/ tan and it should have no power at rest, of course. The input power source to the stop lamp switch is colored grey/ red.

Customer: replied 1 year ago.
I checked that out and yes the center light is on too. Yes the lights stay on when the brake switch is removed. (They'll even stay on if I pull the fuse under the hood.) With the switch removed, or with the switch plugged in to wire harness I have positive power at both wires at the plug in for the switch whether the switch is resting or being pushed. It seems like my test light gets just a hair brighter when on the white/tan when I push the brake pedal. HELP!!!
Expert:  Dodgerench replied 1 year ago.

Unplugging the switch does prove that the brake lamp circuit is getting an outside feed.

I see in the wiring diagram that the L50 (white/ tan) feed splices and runs to the Front Control Module and ABS, but those are inputs to the FCM and ABS, not outputs to the L50 circuit. It's possible that something is backfeeding power into the L50 from either of those sources, but I really doubt it. This almost has to be an aftermarket backfeed. Did you remove the U-Haul converter completely from the van? Or at least from the L50 white/ tank wire?

Customer: replied 1 year ago.
I removed the four way connector and wiring. When installed they rest in the trunk of the van. When I follow the four wires they went under the furthest rear plastic floor cover. With cover removed I noticed factory wiring with three trailer connector wires soldiered together and a ground install on the metal floor with a self tapping screw. There wasn't any box or additional wiring needed for trailer plug. The plug was just extended wires to a four way connector, no extra fuses or wiring. I've owned this vehicle for about 4 years and I haven't had anything installed, nor does it appear anything else was installed beyond the trailer wiring. I have issues with both sliding doors not working, but they never have. My trunk quit working to where I had to open it with a key but when I disconnected my battery, I can use the rear handle to open it now and it will try to raise the hatch. Not sure if that has anything to do with this. It's weird that the first time it happened, disconnecting the battery fixed it. I kinda wish I never replaced the switch as that seems to be what caused this. When I did do this as soon as I plugged in the new brake switch I could hear clicking left of the brake pedal. When I moved that black tap vertical it clicked faster then stopped. Then it worked. 20 min later I came out and the lights were on. I messed with the brake pedal and switch for a couple min and the lights went out. Came out later, back on...
Expert:  Dodgerench replied 1 year ago.

Nah, replacing the switch couldn't have made things worse and while I can't imagine a link to the sliding doors (or liftgate), I do thank you for the extra info. You never can tell.

I figure the clicking noise you heard was from the shift interlock solenoid, which does live in the general brake pedal/ steering column area.

My diagrams suggest there may be something tucked down in the well of the left side brake lamp unit that has to do with trailer wiring. Sorry to keep beating that poor horse, but this seems to be the best chance for finding a backfeed of some sort, so if you wouldn't mind... pull that lamp unit out and check for relays or connectors that you can disconnect. The only "trailer tow" connector on the van is a 6-way unit that lives inside the left quarter panel somewhere that isn't pictured. I figure that all you'd gain by disconnecting it would be to separate the front from the rear of the van, so you could tell which end the power source was coming from, but those quarter panel covers are NOT handy to remove. Not sure if it would be worth it and it would probably apply more to a van with factory tow wiring. Let's see what's in that lamp well next.

Customer: replied 1 year ago.
Nothing behind the left tail light. I pulled off the rear panel and pulled up some of the carpet. Nothing found.
Expert:  Dodgerench replied 1 year ago.

Shoot. We might have to locate the L50 someplace mid-ship and just cut it so we can tell which end of the van power is coming from.

Well, that's interesting. I was looking up operation of the Brake/ Transmission Shift Interlock (BTSI) solenoid... the thing that requires your foot to be on the brake before you can shift out of park... and found that power isn't supplied in the LOCK position. It gets power from the ignition switch in the start, run and off positions (all forward of the LOCK position) and then the FCM underhood supplies grounding to close the circuit. If you had the switch in the LOCK position (or key out) the BTSI shouldn't have been capable of clicking. Was the key turned all the way to lock?

Expert:  Dodgerench replied 1 year ago.

You know what? We could almost certainly find the backfeed source by pulling fuses one at a time under the hood. Everything outside of the Power Distribution Center is fused, so the lights should go out when we find the right fuse. It might help narrow the search down.

Expert:  Dodgerench replied 1 year ago.

And it's got to be a B+ always-hot source.

Expert:  Dodgerench replied 1 year ago.

Just leave that left side brake lamp hanging where you can see it and grab some pliers.

Customer: replied 1 year ago.
That would be correct. I can't shift into gear unless the keys are forward. If the vehicle is running though, I can just grab the shifter and throw it into gears without touching the brake pedal. When my lights stayed on the first time I tried pulling the fuses for the tea lights
Customer: replied 1 year ago.
Tail lights and they all stayed on.
Expert:  Dodgerench replied 1 year ago.

That's a start. Let's see which fuse turns the brake lights out.

Customer: replied 1 year ago.
it's the 20 amp IOD fuse that's supplying power. What's next?
Expert:  Dodgerench replied 1 year ago.

Dang. That sucker goes a lot of places. I'll need to look through the list and see where we go from here.

Wait. Let's take the Front Control Module off. It's the silver box on the front of your PDC, held on with four #20 Torx screws. You may need to lift the PDC off its mounts to get one of the screws, then pry the FCM forward and it'll come off with some difficulty. The FCM is one of the stops for the brake lamp circuit and also makes much use of the IOD, so maybe it's got an internal failure. If the lights go out as the FCM falls off, I think we have our boy.

Expert:  Dodgerench replied 1 year ago.

In the meantime I'll head back to the diagrams to get some more info.

Expert:  Dodgerench replied 1 year ago.

Besides the FCM, the IOD fuse goes to the HVAC control head, audio system (includes optional DVD/ CD changer), Body Control Module, adjustable pedals, overhead console and the SKIM module (immobilizer). There really isn't a good physical connection to the brake lamp circuit on the IOD feed outside of the FCM. With the three bulbs pulling close to 3 amps, I can't quite imagine an accidental harness short between the L50 and IOD because chances are good there would be some heating and maybe fire involved. This problem suggests a diode failure and that would be a good match for the FCM (famous last words).

Customer: replied 1 year ago.
a FCM is around $60 at a junk yard, if that doesn't fix it then what? Am I just gonna have to replace parts till its fixed? Is this something a dealership can plug into and find what exactly is going on?
Expert:  Dodgerench replied 1 year ago.

Did the brake lights go out when you pulled the FCM off? If it did, I'm pretty confident that it would fix your problem. There isn't a good circuit connection anywhere else that I can find.

Customer: replied 1 year ago.
I'll give that a shot tomorrow and get back to you. Thanks for all the help, it's much appreciated!!
Expert:  Dodgerench replied 1 year ago.

OK. You're welcome!

Expert:  Dodgerench replied 1 year ago.

A last test would be to remove or cut the L50 wire where it connects to the big PDC fuse box. Information on the connector colors and shapes are sketchy, but it shows your L50 entering the PDC on a 20-way oval shaped connector in the #17 slot. For lack of a better description, if you were to hold the connector up and look down the barrel (release clasp facing UP), your terminals are numbered from the top row-right to left. Thus, #1 is top-right, #10 is top row left. Pin 17 would be in the bottom row, 7 spaces from the right. If removing the wire from the PDC does it (FCM connected still), it shows that's the place where the feed is originating.

There are 2 other 20-way connectors on the PDC, but only one of them will have a white/ tan wire in that position (I checked).

Customer: replied 1 year ago.
Ok I'll try that. I didn't realize how easy that FCM was to remove, unfortunately that didn't help. I did notice that when I reinstalled the IOD fuse, it took a few seconds for the lights to come on, and when I remove the fuse it took a second for them to shut off.
Expert:  Dodgerench replied 1 year ago.

Rrrrrrrrrrealllly. Like it was being switched on and off.

Expert:  Dodgerench replied 1 year ago.

Did the intensity of the brake lights ramp up quickly, like a switch was thrown? Or did it fade in and out like full voltage wasn't applied immediately?

Expert:  Dodgerench replied 1 year ago.

I've got to go now, but one last thing. Try pulling the IOD fuse with the FCM unplugged to see if it makes any difference at all in timing/ intensity or anything and I'll catch up with you tomorrow.

Customer: replied 1 year ago.
I tried doing that and I couldn't notice a difference. When the lights go on and off it is as if someone is flicking switch.
Expert:  Dodgerench replied 1 year ago.

Well, shoot. The only other hard connections to the brake circuit L50 are the ABS controller and the Body Control Module. Once again, the L50 is used as an input to those controllers, so there shouldn't be any kind of output to the circuit. I think your best chance of a match would be the BCM because it does get an IOD input and you've already got sliding door madness of some sort. The timed nature and flick-of-a-switch nature of the condition would fit the BCM pretty well, but I still can't see how it could accomplish something like this. We'll see.

The L50 enters the BCM at the C3 connector, which is colored black/ white. I think the BCM is mounted with the connectors vertical, but color will be your best reference in case there's a question.

You'll find the BCM mounted up (WAY up) under the driver's side dash, a little left of the brake pedal I believe. You could always disconnect all 6 connectors, but just taking the C3 off should tell us what we need. The vehicle odometer reading and much of the build info is stored in the BCM, which makes it a poor candidate for adoption. A mismatch between two vehicles with dissimilar builds can actually render the van dead -- unstartable. Info only.

Carry on!

Customer: replied 1 year ago.
What I'm thinking is from what I understand the L50 wire coming off the brake switch plug should only be hot when the brake is pressed?. If true, can I cut that L50 at the plug and run my own wires back to the tail lights to power the brake lights? I know I'll have to probably cut the wire behind the bulb also, and I'll lose cruise control, but for an easy fix and needing my brake lights to work, is this something that seems manageable? My concern is that it'll cause a bigger problem, or won't make me aware of another future problem.
Expert:  Dodgerench replied 1 year ago.

Yup, it'll be a bigger problem. The speed control, FCM (for BTSI operation) and ABS need to know when true brake application occurs, so if the rest of the harness stays hot, you'll have problems. It's always tempting to bypass a wire, but I think we need to sort this one out completely.

Expert:  Dodgerench replied 1 year ago.

And keep your eyes peeled for any kind of aftermarket wiring -- anything that looks henky and is tapped into a factory wire. I might not have spelled henky wrong.

Even though you've had the van forever, the dealer will sometimes do kinky stuff with their stock units in hopes of selling a system for extra profit. Then if it's not sold, they either just leave it on the vehicle (shows their total cost investment is pretty low) or they'll stuff a blocker chip into the place where the module (for whatever purpose) was originally. You could drive for years before things go south, but it does happen.

Expert:  Dodgerench replied 1 year ago.

I've got an appointment this afternoon so there will be a few hours where I'm gone... just to let you know.

Expert:  Dodgerench replied 1 year ago.

Back now! Did you try unplugging the BCM?