afnan

Have 2003 accord. Problem is when i open driving side door car does not know if door is open or not. No Map light or dome light comes on. Even with the door open and i insert key and move to position ACC no chimes are heard neither do cluster shows door opening indication.

Other three doors work fine and indication is shown.

I opened the switch and checked for continuity it is fine. Next I grounded the blue connector but still nothing. This leaves either fuse or wire problem. All fuses are fine.

What can i look next into? any schematics?

Lost Again

Does the trunk light work?

Lost Again

Hit send too quick........Pin "P24" at the MICU/multiplex is where the drivers door switch connects.

Back probe it with the door open and see if you continuity to ground. If not and you know you have good ground at the switch.....my guess is that the wire where it goes through the door jam has a break in it.

afnan

Yes the Trunk Light works well. Can you help me with the location of MICU. Would i have to remove the the entire fuse box that seems to be very tough task i think espacially due to working posture in there

afnan

There are two things Door Multiplex Unit inside door and one in Fuse box MICU which one to look for? secondly someone on other forum said that if connectivity is good may be B-CAN reset is all what may be required or honda HDS can tell. What do you say

Following suggest i should look for Door Multiplex Control Unit

tech8

There appears to be few possible inaccuracies/misconceptions in this thread.

1. Driver's door switch harness connector is generally White, whereas passenger door switch harness connector is generally Blue. (However, Honda have been known to have a few color connector differences in model years.)

2. The green wire from the driver's door switch does not run through the door jamb, instead it is part of the floor wire harness and runs directly to the MICU (integrated as part of the under-dash fuse/relay box). The green wire is at terminal no. E15 of a 16P harness connector, which plugs into the back of the under-dash fuse box. -- P24 (a separate harness connector and terminal) is not the same.

3. The driver's door switch is not the same as the door lock switch. The driver's door switch does not go through the door multiplex control unit (MCU). The key-in, key-light reminders, etc. are if the driver's door switch contacts are closed (which would send a ground input to the MICU).

4. With the driver's door open, does the door courtesy light at the driver's door panel work? -- If it works, the driver's door switch probably has sent a ground input to the MICU. If not, then the ground input from the driver's door switch may not be getting to the MICU; which you can do continuity tests of the wires.

professorman

Mine has this problem too. What are the first things that should be checked?

afnan

1. Courtesy Light does not comes on
2. in my car all door switches have blue connector with wires of green color with different color with them. Driver side has Simple green wire from door switch
3. I opened the floor scuff and tested contunity from switch to there. However the wiring seemed to be OEM and fuse box was very very hard to remove so could not test it till fuse box.
4. Can you help me with any diagram of fusebox where to test.?
5. Someone on other forum said to check MICU with honda HDS or Manual doom lamp code to see the problem. what do you say

tech8

HDS (Honda Diagnostic System) is Honda's proprietary hardware/software system. So, unless you want to pay a Honda tech or buy a knock-off HDS to check the multiplex system. In addition, it may just indicate an issue with the driver's door switch circuit; which will still require finding an open or short by other testing tools.

Issue may be either:
- Faulty driver's door switch.
- MICU (integrated as part of under-dash fuse/relay box.
- Short or open wire.

See pictures where the green wire goes to terminal no. E15 of a 16P harness connector, which plugs into the back of the under-dash fuse box. You would unbolt the fuse box. You would then disconnect the 16P connector at the fuse box and the 1P connector at the driver's door switch; then with a multimeter, test for continuity on that green wire.

tech8

You can check the driver's door switch first. Remove the switch, then disconnect the electrical connector from the switch. With a spare piece of wire, insert one end into the unplugged wire harness connector's cavity and the other end of the spare wire touching body ground. - Does the ceiling light turn on?

afnan

Thanks your reply helped me very much.

Tested Following
1. Switch is fine
2. Tested contunity between switch wire and pin you mentioned. It is fine.
3. Tested that pin for contunity with ground. On door open it shows that pin is at ground and not otherwise.

I guess that everything is fine now blame comes on MICU
What do you say if that was faulty it would not work for other doors but everything works fine.

tech8

It most likely is a faulty MICU then. There probably is an open (break) in some component/circuit in the MICU, where the driver's door switch input is not going through.

afnan

I have seen toyota friend disabling things from his cable attached to his computer is there any possibility that previous owner may have disabled the seat belt beep and things like that.

Secondly honda guys suggested me that they can reset the multiplexer to see if it works may be it just requires reset. They said they can plug a connector and doom lamp will tell the trouble codes in mux..........

Can we open mux i know electronics i may be able to check few components and solder them again. Else i suppose entire fuse box would be replaced

tech8

1. See my post in this other thread regarding a battery cable reset (to reset the multiplex system). However, your symptoms does not sound like a reset will change anything.

https://honda-tech.com/honda-accord-.../#post49974562

2. Honda guys can say they can check trouble codes; but, like I said in my previous post, it may just indicate an issue with the driver's door switch circuit. The circuit going to/reaching the MICU is okay based on your testing; it is the MICU internal circuitry that would be left. In addition, why pay a Honda guy to check, when you already narrowed down the possible problem? If you can't repair it yourself, you can use the money to buy a used or new replacement; instead of paying someone to try to read and diagnose an MICU issue and still have to purchase a replacement MICU if it is faulty.

There are no published instructions on opening up the MICU which is integrated into the under-dash fuse/relay box. It is normally just replaced. However, IIRC, someone previously posted some images of him taking it apart, not sure those exist anymore on the web.

3. It is most likely not due to previous owner disabling seat belt beep, etc.

afnan

Thankyou for truly enlightening replies. I am impressed by knowledge you have..... secondly on my cluster battery light and few spedometer back lights also dont come on can it be linked to MICU?

tech8

The gauge control module is part of the multiplex system. However, the MICU should generally not affect the gauge control module. There are numerous SMD LEDS in the gauge control module.

You can always try the battery cable reset to see if anything changes.

DCFIVER

Yes,the Gauge control runs through the MCU. Ive diagnosed and replaced multiple MCUs for various electrical reasons including the gauge not lighting up.


You can try a manual reset of the MCU by simply unplugging all of the connectors. Ive done this many times as a quick go/no go diagnosis. This may bring the MCU back online, but the fix will be temporary.

If it is the MCU,buy a new one(about $250ish) as used ones will likely result in a repeat failure....









(BTW The HDS is not the only tool capable of accessing the MCU. Various high end after market scanners are capable of this also. If you do access it,you are looking for U codes or communication fault codes. Typically there will be several U codes from various modules that are unable to communicate with the MCU)

xci_ed6

speaking of the MCU failure, you ever popped the cover off?

Old main relay's would 'die', but I always fixed 'em with a li'l solder. Usually had them RTR in ~5 minutes.

DCFIVER

Yes,on my mothers '05 TL.


I could not see the fault. I suppose it could have been found under a magnifying glass,but with the naked eye,nada.

BuboCL9

Hello. Sorry for bumping this old thread. I'm inexperienced with vehicles, specially electronics so I just want to check if I understood.
So if the door switch wire has continuity with the pin on that connector, it is most likely the MICU issue?
That connector is on the back of the fusebox, not the ones I can see on the front?
Tried removing the fusebox, but I can't even remove the plastic shroud that goes over it, it gets stuck at the bottom...

The issue I'm having is the driver's door light and interior lights don't switch on and the car doesn't signal that the door is opened.
On all other doors it works fine, the dome lights turn on and the car signals door ajar.
Now, this happened after I noticed the bulb in the door not working, it was actually blinking for a while and then died.
I thought it was a dead bulb, replaced it but still didn't work. Then I noticed the door sensing doesn't work at all.

Everything else seems to be working, the rear windows defrosters, all of the lights and switches...
I changed the driver's side door switch, but it didn't help.
I have all LEDs in my car, the interior, and had them for two years now, not a single one died or anything, is it possible the LED fried my MICU?

It's an Accord CL9 TypeS 2007, btw. European model.
My mechanic is not available, so I'm trying to at least diagnose this myself, so...don't know where else to ask.
Again, sorry for bumping this.
Cheers.