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2002 Sonata Trunk Thinks It's Open

Hi, I’m having a bit of a problem. My trunk light on the cluster gauge will not turn off. I removed the trunk light bulb so it wouldn’t drain the battery but over the span of about a month the battery gets low enough not to start, so I’m assuming its keeping something else on in addition to the light. I only drive about 150 miles a month so it doesn’t have much time to recharge even if it is a small draw. I disconnected the sensor in the trunk but the light is still on, The odd thing is that if I apply high G’s from breaking or accelerating quickly, the light will turn off till I stop accelerating/decelerating (normal driving does not effect it). I’m thinking its probably a short from an aftermarket remote start/security system that was removed. I do not use the factory alarm so I do not care about the trunk sensor being disabled but I cant seem to figure out where to disconnect it from (pulling the fuse did nothing)

I found this website: and I assume I need to find the trunk/hatch pin wire that it is referring to. Or am I going about this all wrong?

Thank you for your help.

The sensor in the trunk is the problem. Replace the sensor.


You could just disconnect the trunk switch and this would fix it unless a wire is grounding out.

Maybe that car uses a mercury switch? If so it may have been knocked out of place. That would explain the braking and accelerating actuating the dash warning light.

I’m not overly familiar with electrical diagrams but if I understand correctly,
When I disconnected the trunk room lamp switch the reason it likely did nothing was because the circuit was still being completed somewhere else since it is not an in line switch.

So by the looks of it I need to cut the wire at the instrument cluster? Im not sure what the ETACM that it links to is but I assume it shouldn’t effect anything if its disconnected as well. Is there any way to tell which wire it is without an ohm meter and a really long wire going to the trunk?

Do NOT cut any wires at the instrument panel!

Disconnecting the switch removing the ground that turns on the light.

I disconnected the switch a few days ago, it is no longer plugged in. The light on the cluster gauge however still shows that the trunk is open. Unless there is a second switch, The one I unplugged was near the latch on the bumper not on the lid.

Im wondering if it might be the light on the instrument panel itself draining the power, I could just remove the light bulb, unless you think there is something else which would still be powered on because of it

Listen to NYBo and stay away from the instrument panel. Is there a chance that you messed with the trunk release instead of the trunk open warning switch ? This might be a case where you should pay someone to fix this problem instead of cutting wires and removing switches and possibly frying your electronics.

I did unplug the trunk release motor and the sensor on the trunk key lock but the issue started before I tried unplugging them and neither effected the light.
I hadn’t thought of it till you just said that but the button on the driver door panel that opens the trunk stopped working about a year ago, I did not think it was related because it was broken in the off position but I could try disconnecting that if you think it might be related.

ATM I have not cut any wires or done anything to the vehicle other than unplugging the trunk sensor by the bottom latch

There is a separate connector for the trunk ajar switch near the solenoid connector.

I looked inside the wire weather casing that goes from the car to the trunk lid and noticed that there are 8 wires in it. As far as I can tell there are only 3 items in the lid, two license plate lights and the trunk release motor which doesn’t add up. I am wondering if Rod might have been right about the possibility of a mercury switch.

It has a common mechanical switch inside the latch, mercury switches were used in the 1960’s.

Just got back from O’reilys (What I should have done to start with), Turns out my alternator is putting out about 11.4V. So a bit of good news bad new, The trunk light isn’t draining the battery but I need a new alternator.

Still doesn’t fix the trunk light but im not concerned about it so long as it isn’t killing the battery. My guess is that when the trunk light drained the battery originally it wore out the alternator.

Thought about it and the trunk switch needs to be made to turn off light. You could put a wire between the 2 pins of the switch connector and prove that’s the problem.

Not according to the wiring diagram. The switch closes to ground both the trunk light and trunk ajar light.

You say you are not worried about the trunk light now. Replacing the alternator, battery and not fixing the light staying on will have you right back where you were. At least take the trunk light bulb out.

I took the trunk light bulb out a few weeks ago, as of right now the only thing (as far as I know) consuming power due to the trunk is the LED in the dashboard which should be taking up less power than the radio clock.
From what I can figure, when the trunk issue first started and I had not considered taking the trunk bulb out (I forgot I had one because it was hidden under an amp), It put constant strain on the alternator, forcing it to recharge the battery which it is not designed to do. which likely caused the alternator to die (it was a cheap unit I installed a few years back).
If you know of any other system which would still be a parasitic draw I will definitely need to fix it, but so far as I’m aware its currently just the annoyance of having the cluster gauge showing the trunk is open.
Part of me kind of hopes the alternator problem came first and caused the trunk light issue since weird things can happen when the cars voltage is low, but I’m fairly sure its the prior hypothesis.

@insightful your right. Switch provides ground for light. It must be getting a ground from a short.

Is there a wiring diagram that shows how the wire travels from the back of the car to the front? I could find the short If I knew where to look