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Discussion Starter #1
I have a 2005 MDX Touring and experiencing a strange, usually intermittent, problem in that the exterior "small lights" at the corners of the vehicle (amber at front corners, red at back corners) and license plate lights in the tailgate will NOT turn off, even with the light switch completely in the off position.

The dash indicates that lights are on, chime warns that lights are on when driver's door is open, but again ... the light switch is in the full off position.

This is usually intermittent, and sometimes open/closing the tailgate seems to shake the MDX in just the right way to get the lights to go out. At the moment, even this doesn't help and my battery is currently being drained by these lights in my driveway.

1) Is there a fuse or relay I can pull to at least cut the power to these lights so at lease the battery doesn't drain? (Dealer tech told me to pull #10 from the passenger side interior fuse box, which is marked "Small Light", but this had no effect ... lights still on).

2) Any thoughts on how I can troubleshoot/repair this problem properly?

Thanks in advance for any ideas shared.
Have a Happy New Year.
 

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If you remove fuse 10 or tail light relay you won't have any rear lights so don't drive. Fuse 10 or tail light relay removal will work to disable temporarily.

Tail light relay or faulty combination light switch are likely faults. Start w/ relay (under dash on driver's side, middle relay on front row of two rows of 3 each relays). Shop manual is suggested.

If relay is not the problem, combination light switch will have to be diagnosed (shop manual) or replaced.

good luck
 

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Discussion Starter #3
If you remove fuse 10 or tail light relay you won't have any rear lights so don't drive. Fuse 10 or tail light relay removal will work to disable temporarily.

Tail light relay or faulty combination light switch are likely faults. Start w/ relay (under dash on driver's side, middle relay on front row of two rows of 3 each relays). Shop manual is suggested.

If relay is not the problem, combination light switch will have to be diagnosed (shop manual) or replaced.

good luck
Thanks ... I've order a service manual/electronics diagnosis manual set. Hoping to receive them this week.

Pulling Fuse 10 seemed to have no connection to these lights ... they stayed on with Fuse 10 pulled. Maybe Fuse 6 "Daytime Running Lights"?

What else controls these lights? They flash when using the remote to lock/unlock, so something more than just the switch on the steering column stick could be at play?

Seems like sometimes even a slight push on the tailgate can have an affect on these lights. Really strange.

Thanks again.
 

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Discussion Starter #4
Ugh. Not fuse 6 either. Lights were still on until the battery died.
Guess I'll jump, charge and disconnect the battery while parked for now.
Nuts.

Thanks again for any ideas (would love to just know which fuse would take these lights out ... much easier than battery dealing with the battery day-to-day while waiting for these service manuals to come in.)
 

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I should have said fuse 10 in the Under-dash fuse box on pax side. Sorry:)

good luck
 

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Discussion Starter #6
Thanks TexasHonda ... yup, it was fuse 10 under passenger dash that I pulled, no effect on these lights. Same with fuse 6 under passenger dash ("Daytime Lights").

Things are getting a little more odd now.
Good news is that after a jump to get things going this morning, lights stayed off.

Strange thing...
Now the power to the GPS screen cuts out if the light switch is in "Off" or "Auto". Selecting the "parking light" or "On" positions restores power to the touch screen (and map lights, apparently they're on the same circuit?).
The GPS computer is not affected. So... with the headlights on, screen has power, I can plot a course in GPS ... but if I select "Auto" or "Off" on the light switch, the touchscreen looses power ... click back to "Parking Lights" or "On", and the Touch Screen comes back, still happily following the selected GPS path.

So ... is there a microprocessor based control unit somewhere that has influence over power to these circuits? Wondering if it's lost its marbles.

Thanks again for any ideas.
 

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padawanNick, Try pulling the rear light bulbs out one at a time untill the lights are turned off, sounds like you may have a bulb with a bad internal filament, It is probably feeding back the circuit.
 

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Fuse 10 supplies voltage to rear tail lights. If lights stay on w/ fuse 10 removed there would have to be either a short to power somewhere in wiring or possibly alternate power supply through driver's multiplex control unit (under dash on driver's side on kick panel). MUX CU ties into to tail lights power feed and may provide an alternate source of power under some circumstances.

Suggest you try removing the tail lights relay to verify presence of short or alternative power feed. This completely opens normal power supply path. Very unusual problem.

good luck
 

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Nick,
Does your MDX have an aftermarket security system or remote starter?

Typically these aftermarket systems flash or activate the parking light circuit.
 

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Discussion Starter #10
Thanks guys. Waiting on the manual and will try the relay.
Again, at this point the lights are now behaving correctly since the battery had drained, but power to the map-lights and GPS Screen is cutting out depending on the setting of the headlight switch (see post#6 above).

There is nothing after market installed in this. I'm the original owner and all service to date has been done by the original dealer. When I took these issues to them (a couple times now) they have not been able to find or correct the problem so now I'm digging in on my own for the first time.

Thanks again for all the input!
 

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So I am having the exact same problem with my 2005 MDX. Lights won't turn off/turn on randomly when the car is off and drain the battery and now the NAV screen will stay on as well sometimes. Did you ever have any luck diagnosing yours? If so what did it end up being? Thanks in advance for any help!
 

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One other thing to check is the wiring harness where the hatch wiring travels into the chassis. Over time the wires get hard and crack from opening and closing the hatch. I'm having issues on my 02 where my 3rd brake light doesn't work as well as the "hatch open" signal to the cluster or the light trigger for the dome light. I pulled back the rubber boot where the wiring goes from the hatch to the body and there were 3-4 broken wires and another 3-4 with broken sheathing about to break. I've also encountered only once my "hatch open" signal staying constantly on which went away when that same section of wiring was wiggled. Just something to check where you may be getting voltage back feeding in that spot through broken wires like I am.
 

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So I am having the exact same problem with my 2005 MDX. Lights won't turn off/turn on randomly when the car is off and drain the battery and now the NAV screen will stay on as well sometimes. Did you ever have any luck diagnosing yours? If so what did it end up being? Thanks in advance for any help!
Im having the same issues with my 2002 MDX
 

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If you remove fuse 10 or tail light relay you won't have any rear lights so don't drive. Fuse 10 or tail light relay removal will work to disable temporarily.
 
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