Yesterday the taillights wouldn't turn off after shut the truck off. Went back in truck, turned it on a couple times and wiggled the light switch. That worked. Now today, the taillights will not turn off when turn truck off. Tried wiggling light switch but nothing. Any thoughts? Other electrical issues going on with dome lights, gas gauge, and reverse camera...but I'll save that for another thread. Got 43K on her already so warranty is gone.

 

Does this happen just from starting the truck, or can you replicate the symptoms just by turning the main headlamp switch ?

If it is just from using the headlamp switch, does it happen only when turning the switch to the headlamp position, or will it do the same thing when you turn the switch to parking lamps ?

If it is from starting the truck, are you manually turning the switch on, or are you using the autolamp position.

Do you have a lamp delay set on the truck ?

Are there any aftermarket modifications ( remote start, HU, etc ) ?

What is the issue with the dome lamps ?

 

I would say it happens from just starting the truck. Today I didn't touch the light switch. I've always had it on automatic. The only change I can impact on the tail lights being on is wiggling the headlamp switch which will cause the lights for a nanosecond to blink. I've tried taking every light related fuse out but nothing has turned them off.

No aftermarket mods on my baby.

No light delay option.

Dome lamps will not turn on unless I turn the cargo light switch on. I can't turn them on either in the front lights or the rear seat.

 

Disconnected battery for an hour. Hooked it back up and the tail lights still stay on. argghhh

 

If you turn the light switch to the off position, start the truck and turn if off again, do the rear parking lamps come on ?

When you say you have pulled every light related fuse, you pull the parking lamp fuse, and they are still on ?

Are the lights on full brightness when you are seeing this ?
The only way to check is at night, have someone turn the switch from off to park, and see if the brightness increases.

The dome lamps, do they come on with the doors open ?

If so, change the interior lamp bulbs.

The elements that come on with the door are separate from the ones that come on when you push the lens.

 

I turned the lights to the off position. I hooked the battery back up, the tail lights came back on as soon as the positive terminal touched. I didn't even get to start the truck up before they came on. I turned the truck on and then off and no change.

The dome lights do come on when I open 3 of the 4 doors. The front passenger door has never activated the lights. I don't ever recall it activating an open door alarm either.

I haven't pulled fuse 42 because I can't find it on the schematic even though they list it in the manual. Is there a second fuse panel location i should look for?

Thank you for the efforts, greatly appreciated and I look forward to anything else you can suggest to try. I am wondering if I should attempt to remove the headlight switch to see if something is amiss in there but not sure if there is value in that.

 

Sorry missed one of your questions. The taillights are not at full brightness. When I step on the brake, the tail lights get brighter.

Seems the only way to shut the tail lights off is to disconnect the battery. Nothing else will shut them off

 

Dome lights - Do they work correctly except for by opening the passenger door ? You made it sounds like the only way they work is with the dimmer switch rotated all the way up.
Sounds like either the door latch is not working correctly or the ground to the door latch is broken ( or could be the wire from the door latch ).
The wires on the front right door is black w/ pink stripe to black ( gnd ).
The wires on the rear right door is Black w/ White stripe to black ( gnd )

These go to the VSM ( Vehicle Security Module ) behind the rear seat back. You can check the wire in the rubber boot between the door and the cab of the truck to make sure they switch to ground.

Fuse #42 should be shown on the lid of the fuse panel, but the 2008 Owners Manual has a typo, it is not marked for some reason. This is the fuse panel from a 2006 OM


This is for the trailer Tow left stop / turn lamp Should not have an impact on the parking lamps being on.

When I asked about the parking lamp being at full brightness, I was asking if the light was burning dim ( back feed from ground ). Stepping on the brake pedal puts on the stop/turn lamps, different element & different circuit.

If the parking lamps are not illuminating on the front of the truck, I am thinking the power is coming from ground. This is why I asked if the trailer tow adapter had something plugged into it ( recon light bar, etc ).

Are you sure this is the parking lamp element in the bulb that is on ?
You would have to pull the bulb, and meter it to make sure it is the parking lamp or the stop/ turn lamp circuit with a low voltage on it.
If the stop / turn lamps are the ones illuminated with a low voltage condition, they can look like parking lamps. This could also explain why the front parking lamps are not on at the same time.

 

The dome lights won't turn on when pressing them or sliding the rear switch to the on position. They turn on either by using the dimmer switch or opening the 3 doors. The front passenger door when opened won't turn on the lights. I will try and find its ground wire and see if it is hooked up or broken or rubbing.

Nothing has ever been hooked into the towing electrical outlets.

Had helper turn the parking lights on and saw that second element light up. So you are right on target, this seems to be the brake element and it receiving some low level power. Took out each tail light bulb but it didn't affect the other one staying on. Wiggled the harness up near the brake pedal, that made the lights shut off for a split second then came back on.

One thing came to mind, the other day I played with the pedal adjustment button. Never knew I had one. Positioned the pedals to a place that fit my long legs better. Perhaps that caused some distress to the brake assembly?
Any thoughts what else I can check?

I am going out to clean the tow wiring harness just to eliminate culprits.

 

For the dome lamps, try replacing a bulb to see if this fixes the map light function. Those bulbs are 2 element bulbs, the map light one could be out. This is from the same circuit off the battery saver relay.

Go back to what you were testing, by pulling the trailer tow stop / turn fuses. These are 42 & 36. I am taking a guess that the hot in run position trailer tow battery pin is shorted to the stop / turn lamps. Big guess, but worth a try.

The trailer stop / turn lamps are directly connected to the output side of the MFS With the brake switch open, the CHMSL would not illuminate by this feed back. Again I am taking a SWAG here.

 

Eureka! Sometime SWAGs are better than being good! Figured out the right turn signal was dead as well (no blinking) so I pulled fuse 36. Viola, the phantom power in tail lights and third light ceased and the lights went off. Lights are still fully functional through their normal control features such as right turn, stop, and park.

I crawled under the truck to look at the trailer plug connections. Did notice the protective cover to the cable no longer covers the actual electrical wires. There is a 2 inch gap now between the cover and the trailer receptacle. Perhaps there is crud now up in the connections. Once it warms up past 11 degrees outside I will take trailer receptacle out and check it over good. Thank you for the outstanding advice and expertise!

For Dome lights I replace for the map and see if that fixes it. Just odd the front and back seat lights went out together. Still wonder if there was an electrical spike that got things out of whack or all is a coincidence. Blew 3 fuses for rear and cigar power last month.

Will work on the front passenger door this week. Gotta be the ground wire or sensor is dead since it doesn't read the door is open when truck is running.

The gas gauge still reads negative gas and there is a huge sucking sound when I open the gas cap. Wonder if a pressure valve(?) is gunked up or the vent tube is clogged up. That is another adventure for another day.

I am going to go to the dealer to get some readings on the ABS.

Still loving my Ford!!!

 

Weather finally warmed up. Got under the truck to look at the tow harness. The wires were in there firmly. Didn't see anything out of the ordinary. Looked inside the plug outlet. Nothing in there touching the pin connections. Is there something I am missing to find if the hot in run position trailer tow battery pin is shorted to the stop / turn lamps. I have a voltmeter so I could hook that up if I knew what to hook to inside the trailer socket for readings.

For gas, found that if I disconnect the battery, I get about 5 seconds after start up of some form of positive reading. With a full tank, it read I had 7 miles to empty. Then after 5 seconds it reads back to negative gas. I am running BG 44k through the system now but not sure if that would clean any gunk related issues with fuel sensor. Is there something I might have in backwards??

 

With the fuses pulled, the trailer tow stop / turn lamp has ( had ? ) a high resistance to the battery tow ( big guess there ).

Quick way to confirm this is to pull the trailer tow battery charge fuse ( Fuse # F106 ) and reinstall the trailer tow stop / turn fuses, and see if the trucks tail lamps go back to dim again.

If not, it could be there was ice in the front or back of the trailer tow adapter with the protective cover pulled back, exposing the inside of the adapter.

If you do have this happen, pull the trailer tow battery charge fuse, and use a meter to check the resistance between the pins, anything more than 0 ohm is bad ( I know, thank you capt. Obvious ) :



Might not be a bad idea to unbolt it from the mount and let it hang and hose it down with WD-40 to clean it out. I would start with the socket facing up, and spray into the socket, letting it run out the back.

Check again with the meter to see if the resistance is still there.

The next place to check for resistance between the 3 circuits ( 2 Stop / turn and the battery charge ) is the connector on the frame, which is connector C411. Easy to get to if you lower the spare tire.
This is the picture from the 2001, but the connector is in the same location.





Wire colors are the same as the socket diagram above.
Check to the side of the connector going towards the truck 1st, checking resistance between Orange ( pin 8 in C411 ) and Dark Green ( pin 12 C411 ) and Orange and Yellow ( pin 11 C411 ).
If this is good, check the side towards the trailer tow adapter same way.

The fuel one had not started ( were working the map lamp thing ), but with this, there was a TSB on high sulfur content fuel that caused faulty readings.
Where do you fuel at, and is it the same brand all the time.

I got one batch ( had to use a non Mobil / Sunoco station ) and got the problem. After a full tank of Sunoco fuel ( was in MI when this happened ) it straightened right up.
The TSB is TSB 08-2-9 for this.

This is the list of the new P/N fuel sending units
PART NUMBER PART NAME
8L3Z-9A213-E Kit - Fuel Sender 2006 starting 12/8/2005 through 2008 - FFV-26 Gal Tank - 126/132 WB
8L3Z-9A213-F Kit - Fuel Sender 2006 starting 12/8/2005 through 2008 - FFV-30 Gal Tank - 139 WB
8L3Z-9A213-G Kit - Fuel Sender 2006 starting 12/8/2005 through 2008 - FFV-27 Gal Tank - 145/151/163 WB
8L3Z-9A213-H Kit - Fuel Sender 2006 starting 12/8/2005 through 2008 - FFV-36 Gal Tank - 145/151/163 WB
8L3Z-9A213-A Kit - Fuel Sender 2004 through 2008 - Gas-26 Gal Tank - 126/132 WB
8L3Z-9A213-B Kit - Fuel Sender 2004 through 2008 - Gas-30 Gal Tank - 139 WB
8L3Z-9A213-C Kit - Fuel Sender 2004 through 2008 - Gas-27 Gal Tank - 145/151/163 WB
8L3Z-9A213-D Kit - Fuel Sender 2004 through 2008 - Gas-36 Gal Tank - 145/151/163WB

Don't know if you want to just order the new one and start there, or try running a different / consistent fuel for now.
Best to get the Vin # for your truck, to get the correct revised P/N when you order it, if you go this route.

 

Wow are your hunches spot on!!!! THANK YOU!! I put fuses 42 and 36 back in, the lights didn't come back on! I will keep an eye on her tonight. Maybe some ice did get caught up on the back side. Given all the rust that has started on the inside of the chrome back bumper in just 2 yrs, I reckon there must be a lot of road spray kicked up. When it gets nicer, I am going to rewrap the wires and protect the backside of the outlet to protect it like it should have been.

Fuel I am pretty much Mobil (85%), sometimes Shell (10%) and once in awhile CostCo gas but that is rare as my MPG decreases significantly on their gas. I'll run her on Sunoco a couple times and see how that does her. I run long so I got the FFV 36 gall tank in her. Maybe after a month I will just install a new fuel sender.

Thank you again

 

I spoke to soon. After 30 minutes, I looked back out and the dim lights came back on. Very very odd they didn't come back on right away when I put 42 and 36 back in. I watched for 5 minutes and the dim lights didn't come back on. Once they were back on, I pulled 106 just to see if that made a difference. It did not. Later this week I will hook the meter to check the resistance between the pins. I just don't get why there was a seemingly time-delay to falsely energizing the circuit. I pulled 36 and the lights shut right off but I remembered last time same thing happened and then the next day the dim lights were back on until I also pulled 42.