I have read other posts on this issue but have not found the exact symptoms (or solution) as mine:

My automatic power door locks wont lock. From my FOB or from the switch found on the driver's door or the passengers. I can only lock my doors manually. When i press the lock button there is no sound coming from the door at all. All 4 doors wont lock.

My doors will unlock fine with the FOB and from the switch inside. Also if I lock all 4 doors manually and press the lock button on my FOB my horn will sound as usually indicating the car is locked and factory alarm is enabled.

I checked the fuse 8 (20A) under the drivers side dash but the fuse seems fine. Also the doors all close properly (ie: the dome lights turn on and off from opening and closing each door).

2003 Accord EX-L 4 DOOR, 4 Cyl 2.4L, Manual Tranny, power everything. 225 000 km

I want to know how to diagnos so i dont spend money on the wrong part...

 

Sounds like the multiplex unit which is part of the fuse box under the driver's side dash. Not too hard to replace the whole fuse box; but, part is expensive unless you find a good one from a salvage yard.

I'll see if I can find diagnostic info. for the multiplexer.

 

I only found the MICU diagnostic for use with Honda's Diagnostic System:

http://www.google.com/url?sa=t&rct=j...jA7Y6Q&cad=rja

Your problem may be also just be a bad driver's door switch or circuit (e.g., pinched wire, etc.), as the system may think the driver's door is not closed, so it doesn't lock the doors. Also see these:

Honda-Tech - View Single Post - 2003 accord Multiplex unit to fix door lock problem?

Honda-Tech - View Single Post - 2003 accord Multiplex unit to fix door lock problem?

 

How about if you use the key in the lock and turn it to lock/unlock the doors?

If that doesn't work then it may be the multiplex unit

There is a TSB on it as well. google "tsb 03-041"

 

If i put the key in the door and turn it (and hold it) it will only lock the drivers door.
I will read the other links from previous reply now..

 

my driver door switch (door jam?) had fallen off and into the hole of the body. I carefully pulled it out with a coat hanger and reconnected it properly. When i push the switch it shows that the door is closed and when i release it shows that the door is open. I installed it back and it seems to be working fine. Since i found the switch like that (fallen off) do you think it has to do with the switch, even though it seems to work now and my doors still can't power lock?
If so should i take the switch off again and test it? how would i test it, what do i look for? thanks guys...

 

Fro the multiplexer, try this reset procedure as described in this link:

Honda-Tech - View Single Post - Help: No turn signals or power locks 03 Accord


Important: You are touching only the cables after they are both removed from the battery terminals.

You will need your radio code after the reset.

 

ok, the way the system works with the key is when you lock the car with the key all locks should lock, when you unlock the car with the key the first bump unlocks the drivers door only, release, then bump again opens remaining doors. i'm going to guess that the door lock master (drivers) switch multiplex unit is defective.

 

It may be related to the door switch, door switch circuit (e.g., wiring pinched, shorting, etc.), multiplexer, etc.

The door switch and checking the wiring is the cheapest and simplest. You did mention the door switch had fallen off, check the wiring first. Be careful of it falling back.

See this attached pic. regarding the lockout prevention of the car, which disables both driver's and passenger's switches. Like what I stated in my earlier post, it may think the door is still open. Also, have you tried the reset procedure?

 

Hello, I have a similar problem with my 2003 Accord. A few months ago, I added an aftermarket radio and everything was great. Then, over the next few weeks, I noticed that the doors sometimes wouldn't lock (with either the key fob or with the lock button on the drivers or passengers side door). Unlock works fine though.

I brought my car to the local Honda Dealer and they said it was due to a faulty master switch. They replaced it, though, and it still won't lock. I have seen some comments about actuators, but if all the doors unlock, wouldn't the actuator be ok? I'm thinking that maybe it is related to the new radio and possibly a faulty ground or connection. Does the locking mechanism run through the radio?

Just starting the diagnostic process with this and I'm wondering where to start. I hope this isn't too difficult (or expensive) to solve. Please let me know if anyone has any suggestions. Thanks.