Hello!

2008 Honda Accord EX-L

About a week ago the light on the dash indicating the driver's door is open began staying on whether it was open or not. I suspected the switch but eliminated that by swapping it out for the passenger side switch and the problem did not move with the switch. I've done TONS of searching but can't find any suggestions other than changing the switch. What other possible causes are there? All the driver's side controls work. I can avoid the dome lights draining the battery by turning them off, but it is annoying because I can't lock the car with the fob and I can't listen to the radio while parked unless I want to also listen to the "key left in ignition" beeping. This doesn't seem to be a fuse problem so I'm out of ideas of what else to check.

Any suggestions appreciated, thank you!

 

It probably is not the switch, since you swapped them and you still have the same problem. I guess you could put the "bad" switch on the passenger side to see if it works just to verify.

You'll have to test the wiring with a volt meter or test light. Does the driver's side electrical connector have one wire or two wires going to it? One (or the only) wire should be brown.

 

Thank you for the reply. It's a single wire, I don't now remember the color, I think maybe white/brown. I believe it to be a ground interrupt. I checked the continuity of the switch before installing it on the passenger's side where It works as intended. I didn't read any voltage with the positive lead of my tester on the wire and the ground lead on the chassis, but I wasn't sure if I would if, say, the wire is grounding someplace upstream. I guess I'll look for a schematic, I just can't think of where else along the path to look without tearing out interior body panels and tracing the wire back to its source. All the other door-open indicators on the dash work like they should. I don't suspect a fuse since nothing else is misbehaving.

Thanks again!

 

From the wiring diagram, the wire color is brown. That brown wire should have 5V to a good ground when the switch is unplugged, so it sounds like the wire is grounded somewhere. You can verify the 5V on the passenger switch.

If the wire is grounded, then the MICU will think the door is open and will behave like you are describing. That wire comes from the driver's side MICU that is on the back of the driver's side fuse box. I'd probably unplug connector D on the back of the fuse box (the only 16 pin connector) and use the volt meter to see if the brn wire has continuity to ground at the door switch.

You can get a 08-10 accord shop manual at automanualsource.com for ~$22 and is definitely worth the investment. The pinouts and locations are shown in there and is a useful tool for DIY work.

The harness goes down from the switch to the floor along the driver's door. Then it turns up for the MICU.

If I had to guess, pin D12 may be corroded and shorting to ground at the MICU connector or the harness got damaged near the driver's door/floor area.

 

Awesome! Thank you for the information and the shop manual source! Just for closure's sake, I'll be sure to post the result this weekend when I'll have the time to look further into it.

 

Well, here's the followup:

I'm stumped, still, but in a better way. I bought the PDF manual, all 2,938 pages of it. After using various search terms, I found a cartoon showing the location of the section of wire harness that has the brown wire leading to the driver's door switch. From there, searching the PDF manual became a time-sink, searching for the wire color abbreviation, BRN, resulted in 198 instances. I waded through many of them but I was unsure I was finding the correct BRN wire in the circuit diagrams. I pulled off the kick panel under the dash fuse box so I could get a look at "the works" and found the 16 pin D connector you mentioned which did have a brown wire leading into it. I did not see any evidence of corrosion or anything else suspicious with the harness or connector. With all the instances of a BRN wire I found in the manual, I was unsure I had the correct brown wire so I pulled more plastic panels to expose the wire harness section containing brown wire leading from the door switch in question and traced it back to the fuse box area.

Here's where it gets weird. The brown wire does appear to be headed for the 16 pin D connector, but before it gets there it leads into a T junction. One branch of the T is the brown wire continuing to the 16 pin D connector and is joined with a brown wire with a white stripe. The other branch of the T has a brown wire that joins a sub-harness section which leads down to a unit that I believe is the receiver for the key fob since it has what looks like an antenna wire leading leading out of it. The unit has a bunch of wires that also run into the unit where the sub-harness leads in, but they are clipped off about two inches from the connector.

I could not find any brown wire with a white stripe in the entire manual using the search function, the wire color code key doesn't mention any brown and white wire abbreviation, both "BRN/WHT" and "WHT/BRN" search terms yield zero results.

And here is where it gets even more weird. This T is a spade connection. Once I unplugged it, everything behaved as normal. All the symptoms I described when I first posted this problem are gone. The T junction doesn't look factory, but what it is I have no idea. I'm neither young enough, agile enough, nor curious enough to spend anymore time trying to fit myself under the dashboard to find out where the brown wire with the white stripe leads. I am satisfied that everything is working normally again.

I spent all the time I had available today on the problem. Ran a few errands, one with the car sitting for about an hour and it started up. As a last data point, when I get home tonight, I will take a voltage reading with the car off, locked, key out, and then take another reading in the morning to look for any appreciable voltage loss. If I don't see anything, I will let sleeping dogs lie and hope that my subconscious won't keep me awake wondering where that brown and white wire leads and why unplugging it would get everything behaving again.

The only thing I can think of after doing more reading in the manual is that by unplugging the T junction I put the MICU into safe mode but I don't understand enough about how the system works to feel confident this is the case. And that doesn't explain the mystery wire.

Thanks for the help.

 

The brn/wht wire from the t-connection is probably something like and aftermarket remote start or aftermarket security system installed by the previous owner. The OEM antenna is built into the ignition key cylinder, so this sounds like something aftermarket installed that was clipped and removed. Somehow the brn/wht wire was grounding along the way, so removing fixed this problem.

Keep in mind if you run into other weird electrical issues that you have some kind of disabled aftermarket unit under your dash. I'd leave it alone unless something else comes up, then I'd probably trace each wire from that sub-harness and remove wires going into t-connections, etc.

If you are using Adobe Reader for the PDF, you can click the bookmark icon on the right to get an index to navigate quickly to different sections of the pdf for further use.

Glad you got it fixed and for posting the final results.