XIV

I have a 2004 Accord Sedan ,My master lock switch is not working. I can manually lock my door from the individual door button and unlocked it from my remote but I cannot lock it from the main unit and remote key. Did anyone encounter this? Any advice please...

shotoutacc0rd

try locking each door by itself one at a time, trying the master switch each time. Come back with results. If say the passenger door being locked allows the master switch to work, we've figured out where the problem is.

XIV

I tried to lock each door one at a time & every time I lock each door I also press the lock key from the remote key but nothing happen except when all the doors are locked & I press the remote key that is the only time it will work.

tech8

May be an issue with either:

• driver's door multiplex control unit (MCU), built into the driver's door master switch
• or the under-dash MICU (Multiplex Integrated Control Unit), which is part of the driver's under-dash fuse/relay box.

The MICU controls the lock and unlock functions.

Although the driver’s door MCU cannot be ruled out, it usually is a problem with the under-dash MICU. That MICU is integrated into the fuse box. 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.

You can try a battery cable reset (to reset the multiplex control system) by disconnecting the negative and positive cables and connecting them together with a jumper wire for 15 minutes. -- Do not touch the battery terminals.

XIV

Do you have any link on how to replace or diagnose the MCU & MICU?

About the battery cable reset, you mentioned disconnecting the + and - cables of the battery and connect them together with a jumper wire for 15 minutes. It will short circuit my battery.How is it going to reset my MCU.

tech8

It will not short circuit the battery, as you are not even touching the battery. My previous post stated: "Do not touch the battery terminals."

You disconnect the connectors from the battery. Remove negative first. Then you use a jumper wire between the disconnect connectors, not the battery terminals.

tech8

A battery cable reset forces all capacitors to discharge faster and clears and reset most control unit volatile memory. Its like removing and reinstalling the battery in a cell phone when it is acting weird or locking up.

XIV

This is how I understand it , take out the MICU from its connection, remove - first and then + , use a jumper wire and connect + from the MICU to + battery & - from MICU to - battery. Am I getting it right?

tech8

No. You will not be going near the MICU during this.

Honda has two different methods for the battery cable reset.

1. The method I posted previously is to disconnect the negative cable (disconnect negative first) and then positive cable. Then connect them together with a jumper wire for 15 minutes.-- Do not touch the battery terminals. You'll need the radio's anti-theft code afterward.

2. Honda has a variation of the battery cable reset which requires turning the ignition on and off; but, only requires 10 minutes. I will post the Honda Service News excerpt temporarily.

The 15 minute reset doesn't require turning the ignition ON, etc.

tech8

Like this:

XIV

How is the second battery reset work?

XIV

Thank you for the diagram . I will try it and post the result .

shotoutacc0rd

Honda has a variation of the battery cable reset which requires turning the ignition on and off; but, only requires 10 minutes. I will post the Honda Service News excerpt temporarily

well?

tech8

The Service News excerpt was an image which I only posted temporarily and removed in post #9.

johnsc2235

Could just be a bad drivers door lock actuator. So let me understand this, you try and lock the doors with the remote and they all lock but they don't all unlock?
If you can Lock or Unlock the doors and the other way does not work, such as if the car can lock all doors but does not unlock them, or you can unlock them all once they are all locked but cannot re lock them, try hand locking the problem door or hand unlocking the bad door and see if the rest of the doors work. If the drivers door lock is stuck in the lock position you will not be able to unlock the other doors with the remote and vice versa...Make sense?

tech8

+1. Forgot about that scenario.

shotoutacc0rd

That was the first trouble shooting diagnostics processes i gave him. In my experience it has been the rear doors, I was unaware a bad driver's door exacerbated the issue.

thank you for clearing up what I tried to say though man, and expand on it :thumbsup:

tech8

Although an actuator is a possible scenario, the driver's under-dash MICU is a known cause of exactly what the OP is describing for the 2003-2005 Accords. Certain Acura models had the same issue.

It was published as part of a March 2009 Honda Service News.

tech8

The issue describe would generally not be due to the rear doors or passenger front door. So, what johnsc2235 wrote is different than what you wrote.

VeeSykkz

replace master switch?

XIV

Do you happen to have a picture or diagram or even a how to replace a MICU ?

tech8

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.

It does sound like it is related to the MICU though.

That MICU is integrated into the fuse box. 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.

This service bulletin is for a V6 coupe which may be a different fuse box part number than for your car; however, I am posting it to give you the basic fuse box removal and installation instructions. -- I recommend you download it immediately, as I may remove it later.

XIV

Do you mind reposting the article or send it to my email?

tech8

I'll just re-post this article for a short time. Please save the image immediately, so I can remove it. Also, download the service bulletin in my previous post.

XIV

Thank you for all your help.........