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Doug, ASE Certified Technician
Category: Mitsubishi
Satisfied Customers: 8536
Experience:  Mitsubishi employed and Factory trained ASE certified technician
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My 2006 Eclipse GT has the headlights stuck on all the

Customer Question

My 2006 Eclipse GT has the headlights stuck on all the time... even when the key is out. I've checked all the fuses under the dash, and under the hood - all good. Removed the relays under the hood, won't switch the headlights out. The only way to shut them off is to remove the battery or take the headlight bulbs out. Alternator fuse under the hood is good. Any suggestions? I am a GM mechanic, but before I go hunting for shorts to power, I thought I'd ask you guys as you'r
Submitted: 2 months ago.
Category: Mitsubishi
Expert:  Doug replied 2 months ago.


It sounds like your front ecu is stuck. The headlight switch sends a signal to the front ecu, which is more or less a glorified relay pack, which then delivers power to the appropriate lighting fuses in the fuse panel to turn the lights on.
Basically your only likely scenarios here are going to be a faulty front ecu, or damage to the wiring between the front ecu and the switch (giving it an erroneous "on" signal). The latter is not likely however, because if this were the case the lights would still time out like they do when you leave the headlight switch on/key off and open the door. The front ecu wouldn't know the difference and would still turn the lights off. Technically there is an ETACS in the middle (Which is what controls the auto-off), however if that were the problem, we would expect the headlight switch being turned off to still turn the lights off, since the switch over-rides the ETACS.
Since you are seeing the lights on at all times no matter what, I'd say it is super strong for the front ecu.

I would go to the under hood fuse panel and pull the front ecu (the big ~3"x2" "brick" device in the fuse panel... usually black or red). Confirm the lights go out. If they do not... then there is a short to voltage most likely in the fuse panel itself.
If the lights go out, make sure the headlight switch is off, and then plug the front ecu back in and see if the lights turn on. If they do not, then try manually turning them on and see if they get stuck again etc... if they do turn on, pay attention to if you hear the relay inside it click when you plug it in. If the front ecu clicks and the headlights turn on, anticipate a short between the switch and the front ecu. If the front ecu does not click, but the headlights turn on when you plug it back in, expect the relay inside the ecu is stuck/shorted.

Customer: replied 2 months ago.
Thanks for your reply. The lights remain on when I pull our the front ECU. I also did the DRL delete during the diagnosis to rule out that function. I also replaced the switch on the column.
Expert:  Doug replied 2 months ago.

No problem..... if you pull that front ecu out and the lights stay on, there is something amiss in the fuse box or from there outward. No exceptions on that one, since the front ecu is what delivers the power to the headlight fuses to turn the lights on. If the front ecu is missing, those fuses should never get any power.

There aren't any other modifications to be aware of right, no HID conversions, no front end damage recently repaired etc?

Expert:  Doug replied 2 months ago.

For reference, I'm attaching the relevant portion of the schematic so you can see what I'm talking about.... if that front ecu is out, there is no natural way (like component failures) for the headlights to get voltage. It would have to be something in the fuse box forward.

Customer: replied 2 months ago.
No mods, no accidents. I notice the 7.5 amp fuse for low beams has power on both sides with the ECU out and the column light switch in the off position. There should only be power there with the switch on - correct?
Expert:  Doug replied 2 months ago.

There should only be power there with the front ecu installed for starters... but yes under normal conditions the headlight switch being on would tell the front ecu to power the fuses. If you look at the schematic you'll see those fuses are fed directly off the front ecu... if that front ecu is removed and there is still voltage on those fuses, the problem is from there forward (zero concern over switches, ETACS, etc).

Take one of the low beam fuses and remove it and see if the headlight goes off... if it does, then you know the short is definitely in the fuse box. If the headlight does not go out, then the short is somewhere after the fuse (possibly fuse box, but also possible to be anywhere from there to the bulb, backfeeding to the fuse).

Customer: replied 2 months ago.
If I pull out all the headlight fuses and the ECU they still remain on! Only way to turn them out is to disconnect the battery or pull the headlight bulbs There's a couple of threads on Club 4G pertaining to this issue, so it's not a totally unheard of problem. One Just Answer technician answered that there is a recall on the headlight switches on these cars, take it to the dealer for that recall. But I tried a new switch. I was hoping that you guys new more than I did. I already suspected a short to power as you can see in my original question.
Expert:  Doug replied 2 months ago.

Yeah if the fuses are out and they are still on, you have wiring damage, short to B+ somewhere there.
There isn't really any specific areas of concern on this model for that (why I asked about accident repairs). This model/year is not known for really any wiring issues in general, let alone headlights. At this point you are going to need to start tracing your wiring either inside the fuse box and forward or backward from the headlights until you find damage.

Expert:  Doug replied 2 months ago.

I'm not sure about any forum issues.... its certainly possible, but that would be a small percentage of the whole. As for the erroneous post about a recall, I'm sorry you got that message. We have had some issues with expert quality in the past few months, hopefully that will be corrected soon. (That recall is for Lancers and doesn't even apply to North American markets).

Customer: replied 2 months ago.
Ok thanks. I'll start pulling wires from the fuse box forward.
Expert:  Doug replied 2 months ago.

You're very welcome, good luck!

Expert:  Doug replied 2 months ago.

And yeah... I would do the same with starting at the fuse box; while I know it isn't any fun opening that up, it is much easier to have a short to voltage in there than having harness chaffing-type short and affect both sides etc.

Customer: replied 2 months ago.
Do I pay for getting what I already knew reiterated?
Expert:  Doug replied 2 months ago.

That's your call; I have no way of know what you (or anyone) has determined on their own prior to getting here, I can only address the facts as presented to me. I'm here to answer your questions and help in any way I can. If you don't feel I did that, and you don't want to pay, that is your choice. We do not get paid at all for our time if you do not give a rating. If you feel that I was honest and helpful with the situation and answered your questions accurately and timely, then a rating would be appreciated.

Customer: replied 2 months ago.
Gotcha. So the service collects it's money regardless of rating?
Expert:  Doug replied 2 months ago.

The way the site works on per-question accounts is they take a deposit when you open a question, then when you issue a rating the money is distributed. If you do not issue a rating, the money remains in your deposit for future use, or can be refunded if you contact customer service.

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