So I've discovered another couple electrical issues with this 06 Mark LT.

I noticed that the backup beeper doesn't work.... at all, and my 7 pin trailer plug only partly works.

Today I backed the truck up to my camping trailer to check the 7 pin. I don't have a trailer with a 4 pin to test that one.

On the 7 pin, ONLY the parking lights work... I think. I did not test the brakes themselves, only lights. The left turn signal, right turn signal, and brake lights do NOT come on the trailer, but they all work just fine on the truck. I am absolutely bewildered at how only the parking lights work. The ground is on the top of the frame rail, and looks to be a bitch to even check, but it feels tight to tug on. I know a good ground test is not the "tug test", but if the park lights and the others share the same ground, then that wouldn't be my problem anyways. Where would you start looking, do the brake light and signal light pins share something that the parking lights don't?

Do the backup sensor system and the tow connector share anything in common by chance? Damn I wish I had a owners manual.

I read a thread on another guy's backup sensor problem, and the whole thing seemed like it was a complete disaster of a system. Maybe I'm overthinking it, and my problem is simple... but that's not usually how things work out in my life. I can tell you that the truck has nearly a quarter million km on it, and the sensors in the bumper have taken some abuse over the years. They all seem to have little chips out of them or some defect, as if the truck did a lot of gravel road towing in its life. Who knows.

How do you test individual sensors for function? How can you test the beeper to see if it actually makes noise? Where to start......

 

you can download your manual right here:

https://owner.lincoln.com/tools/acco...coln/Mark%20LT

As for the lighting problem, there are some fuses related to tow lighting. You'll find their locations in the manual. Otherwise it's likely some bad wiring.
Good luck,
Gene

 

By "backup beeper" do you mean Park Aid module ?
- Do you know that the truck came with one from the factory ? I think the PAM button is in the center trim panel by the cigar lighter, to turn it on & off; at least on a F150 that is where it is.

The truck's reverse lamps, PAM and electrochromatic mirror are all from the Dark Green w/ Yellow stripe wire from the DTR ( Digital Transmission Range ) sensor on the side of the transmission. This is what turns the PAM on, there is also power to the PAM as well as the sensors on the back of the truck.
- You will need to watch if the PAM turns on and then off straight away, as this is a sign of the PAM sensors having failed, not an issue with the PAM itself.

Do the truck's reverse lamps work ?

On the 7 pin, time to get a meter and check what does and does not work.
- Keep in mind, some of the functions are only hot in the run position on the key.

The Stop / Turn on the trailer are 2 fuses ( one left, one right ).
On the F150 they are F36 & F42; this is a fuse that is off the truck's stop / turn circuit ( no relay ).

Parking lamps is a relay and Fuse F10.

You will need to get a meter and check each of the 7 pins, to see what is and is not working on it.

 

Sometimes the simplest answer is the right one. The left and right sides for the trailer harness have their own fuse. Both were blown, probably related to the bent mounting bracket under the bumper and the mashed up 4 pin. I replaced the fuses and all tail lights work on the trailer. Go figure.

I haven't gotten into the backup sensor issue yet. As soon as I put it in reverse, the little switch on the dash above the ash tray switches off after one steamboat. (ya this thing has an ash tray... Need a mod for this space)

 

Yes it has a button, and yes it turns on and then off after a second, if that. The auto darkening mirror works. I tested it with a flashlight at night, and it works perfectly. The reverse lights also both work.

If this all means that I have a bum sensor... how do I go about testing them individually to see which, or how many are toast? Is there a way to bench test them at all? If I am going to a wrecking yard to scrape one up on the cheap, it is nice to know its a good sensor before I leave....

 

That is 90% a sensor issue.

Don't try to bone yard them, you will not have any long term luck with that.

Go buy a set from Tasca or one of the other online Ford dealers that sell parts online.

 

Tasca lists them at 110 each.... Ebay or amazon has aftermarket ones for 30 to 40 for a set of 4. Any horror stories on the cheap knockoffs vs OEM?

 

I've ordered the ebay cheapo's. Lets give er a whirl...

 

Well..... That didn't appear to work. I ordered 4 sensors off ebay, and also discovered that the connector on the left outboard sensor was destroyed by green death. I picked up a connector from a boneyard and soldered it in. No change. Im not totally convinced that the ebay sensors are working, but the seller has had nothing but positive reviews on the sensors.

I readseveral comments on here about listening to the sensors tick rapidly from a close distance to yoyr ear to isolate a bad sensor. None of mine tick.... Not before and not now.

Start truck and the switch on dash is fine. Drop it in reverse and within a second the switch turns off.... It did this both before and after the splice and sensor replacement.

Thoughts?