I've been through this and other forums pretty thoroughly and can't *quite* find the situation I'm facing.



This is a 2002 Honda Accord my partner has had since it was new. The main symptom is running lights (amber front/side red/rear) won't turn off and remain on with the vehicle off.

Recently the battery was dead (dead-dead 0 volts, wouldn't take a charge), it was about 7 years old, so I bought a new battery @ Autozone. For whatever reason, they cross-referenced it wrong (I didn't bring in the core at that point) and they sold me a battery that was almost precisely the same dimensions but the poles were reversed and I didn't pay enough attention to the embossed + / - symbols. When I hooked up the cables there was a bit of an arc and the horn blared. It was a fairly short contact but I did "try" it a few times, thinking it was the factory alarm triggering... eventually I figured out the reverse polarity and looked up the fitment guide, took the battery back (with the core) and got the right one this time. Hooked it up with no problems but got no power at the ignition key... pretty quickly determined that the 100A fusible link in the main fusebox (under hood) was fried) and replaced that. At that point we were back in business (or so it seemed).

Unfortunately the parking lights now remain on. I went through everything I could think of as optimistically as possible.

1. My first hope was the multifunction switch which I disconnected (lights still on) and checked for continuity/shorts (all working correctly).
2. Checked power/fuse continuity at the fuse (passenger side 8 or 10 I think) finding that there was *power* on both sides of the fuse, consistent with another circuit feeding the lights in parallel to the multifunction switch.
3. pulled the radio/console to see if the aftermarket stereo in it was wired wrong or shorting (as per many reports) the illumination wire. The radio *had* failed at the point of dead battery/reverse polarity??? which was resolved with a 20A fuse in the back of the stereo head unit. I assume blown by the reverse polarity?
4. Read every wiring diagram in the online repair manual I could find...
   1. Determined this model is not CA with DRLs
   2. Determined this model did not have the auto-off (therefore no relay). Could have been a stuck-on relay?!!
   3. Determined that the offending extra power will almost surely be on a red/black wire, probably leaving the drivers multiplex to a front and back harness connector... connected where/how I can't guess.
5. There is a red/blk wire coming out of one of the easy-accessible connectors on the Drivers side fuse box where the multiplex piggybacks, but disconnecting that connector did not resolve the problem, nor was there power to that pin even while the parking lights are on... so a completely different Red/Black it seems.
6. I've taken pictures under the dash as well as looked at these modules for sale on E-bay with the wires cut, connectors in place to try to find a red/blk wire to probe... not obvious!

What I'm hoping for is:

1. Someone else has been through this and has more hints for what to check
2. Someone is better at deciphering the circuit/wiring/pin diagrams and can maybe tell me where that Red/Blk wire might be leaving the fuse-block/multiplexer.
3. Someone could help me guess how to A) find this wire and B) if there is any good reason that cutting it would have other side-effects.

Here is my logic:
Either before the reverse polarity incident or because of it, the multiplex unit got slightly scrambled. I believe that it's only "play" in the parking lights is probably to flash the lights when alarming or when arming/disarming the alarm? And maybe to detect "lights on" so it can beep the chimes at you.

This is supported by the fact that when I turn off the car and remove the keys, the "lights on" chime is going (as it would since the lights are on!).

Another hint might be that now the SRS warning light is on... which suggests to me that either that the multiplexer is fried enough to light that when not needed, or more likely my polarity reversal triggered something with it. I will go through the steps to reset that SRS (the fancy pull the connector, short the pins, turn it on, unshort, turn off reshort, blink twice... etc. thingy).

I *have* found a used drivers side multiplexer (38800-s82-a03) on e-bay for under $30 which I may order to have in hand if/when I get the guts to tear out the whole thing. I hate "trouble-shooting by arbitrary replacement"... but I'm pretty much at wits end.

To add insult to injury, we are ready to replace this car with something new(er) but I am loathe to hand off anything with known or potential problems even at a huge bargain unless it is to someone with more troubleshooting skills than *I* have... so I'm still banging away a this *even* if I end up donating the car to someone in need. It has nearly 200k on it and except for faded paint and this weird electrical anomaly it is going strong and has *brand new tires* (unless what we upgrade to takes the same size wheels and then we may swap them over). In it's whole life it has had nothing but fluid changes, tires, brakes and the 100k mile timing belt (probably overdue for another?).

Right now, I have a battery disconnect switch under the hood so we can avoid running down the battery anytime it sits for more than 10-20 minutes. I made it in/out grocery shopping this evening without running the battery down... but had to fend off good samaratens telling me "hey, you left your parking lights on!"... not a good long-term solution for me or the next victim-owner.

Any thoughts/ feedback/advice, links to better pinout specs (esp. for the multiplexer) would be very welcome.

 

Hooking up the battery backwards either damaged a component or melted/shorted two wires together. You may also have multiple blown fuses.

Search youtube for how to quickly test for fuses. A test light makes quick work for testing fuses. Replace any that are blown. Check that they remain intact. Post any fuses that were blown and also any fuses that continuously blow.

I'd probably hook up the battery, then pull fuses one by one until your parking lights turn off. Pulling the #10 fuse in the passenger's fuse box should shut off the parking lights.

 

PAhonda -
Thanks... I *have* been through every fuse in the fuse-boxes and the only one that was blown was the main 100A under-hood, though I understand other things could have fried before *that* went out. The radio internal fuse was blown as well, I don't know what that might imply... it is replaced and now working. I've gone through all the vehicle electrically operated items and can't find anything not working... the only malfunctions I can find are the parking lights not turning off and SRS warning light on.

#10 has power on both sides of the fuse... indicating to me that "yet another circuit" is feeding the wire-harness downstream. The only things I find in the wiring diagrams that *should* be able to do this are:

1. Automatic Lights off Circuit
2. Daytime Running Lights Circuit
3. Alarm system (via Drivers multiplex)

1. is supposedly only on the EX model and in fact, I have no relay. Otherwise *it* might have been fused closed?
2. only on the Canadian model and the parts that go with it are not present.
3. this may not be my last hope but it is the last one I have identified.

Another hint as to the source of the problem is that the dashboard/gauge illumination does NOT stay on with the running lights as it does when the switch is on.

I also have been wracking my brain (and searching the wiring diagrams) for any "always on" source of power the parking light circuit could possibly be shorted/fused to.... if I can find the parking light harness(es) (front/back) and disconnect them independently I think I can eliminate that one or the other is shorted to always on power? That leaves shorts in the fusebox itself (and of course the dastardly multiplexer).

I'm about 3 weeks in on this circuit tracing adventure... I started driving it again yesterday just to see if I can notice any hidden or cryptic problems.

Any help on finding the pinout descriptions on the multiplexer, the harness connector IDs for the rear harness would be helpful... I doubt it will change things but once I go through the SRS reset operation I may get some more hints of what it is(n't)!

 

Looking at the wiring diagram, the #10 fuse will always have power. If you unplug the #10 fuse in the passenger side box, do the taillights turn off? This test can eliminate half of the circuit/wiring.

 

I have iteratively removed each L/R under-dash fuse, including the #10 (my first hope!). The lights remain on in all cases. With the #10 fuse *out* my multimeter shows power on the component (light) side of the fuse. The power side of the fuse is hot or not based on the position of the switch (as expected). One of my first trouble-shooting tricks was to remove (and check) the multi-function switch. Its continuity was as expected for each switch setting and disconnecting the switch did not interrupt the parking lights. I had hoped it was a fused closed switch...

Power is getting to the wiring harness(es) somewhere beyond the switch (and #10 fuse). Wiring diagrams suggest that is possible via the "automatic off" light relay (which this car does not have), the daytime running lights (which this car does not have) or the alarm system (to flash the lights when arming/disarming or alarming).

I haven't tried wholesale disconnecting of wiring connectors from the fuse blocks... that might at least help me understand the wiring harness setup (and eliminate wiring closer to the lights themselves being the source?) I will probably try that next... I am somewhat (not) limber so squirreling around behind the fuse blocks disconnecting connectors beyond the ones on the front is very difficult for me.

 

I'm trying ask questions about what you tested to maybe narrow down the problem. Sounds like you've done more testing than most before posting on here. My apologies if you already did some of my suggestions, because I just read your first post and I missed some of your steps. Just trying to narrow down the root cause.

I'm guessing you purchased the 98-02 shop manual pdf from a site like automanualsource.com that has wiring diagrams or some equivalent? Is your car a 4-cylinder or V6? I don't think this will make a difference.

The power going on/off on the light side of the parking lights is very strange. The shop manual doesn't have a great pinout of the driver's side MICU and some of the wiring is connected directly to the driver's fuse box. You may be able to narrow down the power source by pulling the 40/50 amp fuses in the engine bay fuse box to see which one turns off the parking lights.

My guess is that the driver's fuse box, MICU, or possibly the under hood fuse box got shorted when the battery was connected backwards. Fused wiring in the harness or connector is also a possibility. My best guess would be a short in the driver's fuse box. I'd probably go to a u-pull-it junkyard and get the whole drivers fuse box/MICU assembly.