I have a 2003 accord ex-l sedan V6 AT with power door locks and keyless entry. The issue I am having is that the doors will lock via the switch or keyless remote. Unlocking works both via switch and keyless. I can lock them manually by pushing the **** down on each door(1 by 1). if I put the key in the drivers door and lock it, only the drivers door will lock.

Looked online and in the FSM, all pointed to actuator. I changed drivers door actuator, no dice. After I replaced the actuator, it seems like all doors unlock when I unlock the drivers door with the key. Sometimes when I shut the drivers door (without locking) the alarm will activate and go off when I open the door again.

The door switches seem to work, when doors are opened the dome light comes on as it should and goes off when doors are shut.

Anyone else have this problem? Could it be the MICU?

 

A little strange that it can lock with the driver's door lock switch and remote transmitter; but, not by the driver's key cylinder switch.

When you use switches from the driver's master switch (i.e., driver's door lock switch or driver's key cylinder switch), all lock and unlock commands from these switches are communicated across the multiplex communication line (i.e., a one wire B-Can communication line) to the multiplex integrated control unit (micu) located in the under-dash fuse/relay box. According to the switch request, the micu located in the under-dash fuse box, directly operates the power supply and the grounding signals to the reversible electric door lock motors for lock and unlock modes. Inserting the key into the driver’s key cylinder switch and turning the key one time will unlock the driver’s door. Turning the key a second time will unlock all the doors. This is a multiplex controlled response.

The receiver antenna for the keyless system is located in the power window master switch (door multiplex control unit). It uses the same one wire B-Can communication line to communicate to the MICU in the under-dash fuse box.

It may be a problem with the Multiplex Integrated Control Unit (MICU), which is built into the under-dash fuse/relay box.

1. Do a battery cable reset by disconnecting the negative and positive cables and connecting them together with a jumper wire for 15 minutes. -- Do not touch the battery terminals.

https://www.hondaaccordforum.com/for...ine=1411506130

2. If that doesn't work, the MICU may need replacement.

I usually don't like to make recommendations to replace parts without proper testing; however, there is no easy way to test the MICU without the proper equipment and procedures; additionally, diagnostic at the dealer will not be cheap.

If it required replacement, the entire interior fuse box on the driver side is replaced. Only two bolts hold the fuse box in (one bolt at the bottom and one bolt at the top left of the fuse box). You have to transfer the relays and fuses to the new one. Honda does not recommend using pliers to remove the relays, as you can damage the relays that way.

 

Thanks for the reply, I may have typed my OP wrong.

Press Unlock on either door switch or keyless remote - unlocks all doors
Press Lock on either door switch or keyless remote - nothing happens
Put key in drivers door and lock - only drivers door locks, other 3 stay unlocked

I will try a battery cable reset and report back

 

I tried the battery cable reset, didnt change anything. I just noticed that if I press the lock button on the key remote while the front passenger door is unlocked - nothing will happen. If I lock the passenger door manually and press the lock button on the key, the lights will flash but the car wont actually lock. Possible problem with the passenger door wreaking havoc on the system?

 

The way it sounds to me:

• More likely a problem with under-dash MICU.
• Lesser possibility of issue with driver's door MCU.
• Probably not an issue with passenger door affecting multiplex system.

 

I have ordered a new MICU and currently waiting for it to get here. The locks decided to randomly start working again, we'll see how long they work for now.

 

So i have replaced the underdash MICU today. Seemed to fix the issue with the alarm arming when i close the drivers door (just closing it, not looking). The only remaining issue now is when the car is on and i close the doors they automatically lock.

 

The remaining issue may be due to either of the following:

• Black ground wire that goes from the driver's door lock **** switch to grounds G501 and G601. The point of weakness may at the area of the driver's door jamb. Check the wiring that runs through a Blue/White colored connector (C632) at the door jamb. You will have to gently pull off the rubber cover to see it.
• Intermittent open in Wht/Blk wire that runs between the driver's door lock **** switch and the driver's door multiplex control unit (MCU)
• Faulty driver's door lock actuator (probably not the issue, since you changed it before)

The Wht/Blk harness wire can be tested for continuity after you unplug the harness connector from the actuator side and the driver's door MCU. To test for continuity, set the multimeter to either the "ohms" or the setting it will beep when you hold the two leads together.

• If your meter beeps, it means you have continuity.
• If it is on ohms scale, you will have continuity when it reads close to 0 ohms.
• If it doesn't beep , shows OL (open line) or a 1 (infinity ohms); it means you don't have continuity.

************************************************** *****
There was a July 2005 Honda Service News article:

Power Doors Lock By
Themselves or Cycle Twice
NOTE: This article applies to ’03–05 Accords,
’05 Odysseys, and ’06 Ridgelines.
An open (ungrounded) driver’s door lock ****
unlock switch can cause the multiplex-controlled
power door locks to lock by themselves or to
cycle twice to unlock and then lock.
What’s going on is the multiplex control unit
"thinks" the driver’s door is locked. To try and
restore the unlock signal, the system unlocks the
door twice. The system then goes back to its
default position by locking the doors.
To fix this problem, here’s what you need to do:
1. Connect the HDS to the 16P data link
connector (DLC). Turn the ignition switch to
ON (II). Turn on the HDS.
2. At the screen prompts, enter the VIN and the
odometer reading.
3. From the Select Mode screen, select Honda
Systems. From the System Selection
Menu, select Body Electrical.
4. Select Door Locks, and then select Data List.
5. Scroll down to the driver’s door lock (unlock)
data, and read the screen. The list says ON
when the door lock **** is unlocked; OFF
when it’s locked. If the driver’s door lock input
is incorrect, go to step 6.
6. Check for an open circuit in the WHT/BLK
wire between the door multiplex control unit
and the driver’s power door lock switch. If the
wires and connections are OK, go to step 7.
7. Check the lock **** switch ground. If it’s OK,
then replace the driver’s door lock actuator.

 

Thank you kind sir! Will try and report back

 

Thanks to everyone who's helped. I had an Intermittent open in Wht/Blk wire that runs between the driver's door lock **** switch and the driver's door multiplex control unit (MCU). Got her fixed now!