For about 1 Year now my Honda is acting up. The car locks and doors with the key in the ignition whenever a door is opened and closed. The remote control is seems to be working fine however I cannot roll down the windows using a key on the door lock. I had to replace the door lock actuator on the driver side over year ago. Today I tried the remote to open the door but nothing was happening. When I tried to use my key to open the door the alarm went off. about a minute later I was able to drive off when the alarm shut off. I wasn't able to roll the windows up or down or lock the doors for the whole ride. When I got home about 30 minutes later and I shut off the engine was working again. The shop manual states that an MPCS connector is needed in order to run diagnostics. Where can I get this connector? Are there any stores selling it? Does anyone know what the actual problem is with a car lock mechanism?

 

Get your car battery checked. When was the last time it was replaced?

A low battery charge can caused problems with the multiplex integrated control system (mics).

Keyless entry, power door locks, security system and the power windows run through and are multiplex controlled.

 

Just changed oil past Saturday and battery was load tested. I am just curious about this multiplex issue. Is there any diags I can do to it without Honda specialized tools?

 

1. Visually check the battery terminals and cable connectors are okay.

2. The multiplex control system is not something you can easily diagnosis without Honda diagnostic software/tools.

3. 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. Note: Disconnect the negative cable first.

You'll need to enter the radio security code afterward.

 

Here is another update. This happened again this afternoon while leaving work. Apparently the alarm now cannot be disarmed by both fobs. I can only open the door with the key and drive off and the alarm still goes off. The red alarm led keeps blinking and I cannot open and door locks or windows. I will try to disconnect the battery to see if it makes a difference.

 

I followed your advice and disconnected the battery. As soon as I disconnected I was able to deactivate the alarm and the fobs worked right away. I also tried to discharge the whole system by connecting the car side battery terminals. I am back to the point where the alarm works but the car will double lock the doors when you have the key in the ignition. Also windows do not roll down via the fob. Unfortuently I might need a Honda HMS to troubleshoot the system. On plug the service connector on the multiplex unit.

 

For the remote issue, try reprogramming them. This link instructions should still work for your 2005:

http://www.driveaccord.net/PDF/remot...m%2098-011.pdf

 

I believe I found the issue. It seems for some reason the key lock cylinder sensor stopped sending signals when the door was closed. This sensor has three contacts one pair makes contact when the door lock is opening and one pair makes contact when the door lock is closing. I was able to bend the pins using a multimeter probe. After this change the contacts seem to be working. I can now see the alarm light going on when the door is locked and turn off when the door is unlocked, also the lights seem to be turning on. The car now does not attempt to lock the doors when they're already locked or open and the door is open and closed. I can now also roll down the windows using a key in the key lock. That seems to be the issue. I am just puzzled why I couldn't turn the alarm off the fob.

 

I'm trying to make sure I understand where the issue was. Was the problem the lock cylinder switch, like in the attached picture?

 

Correct. It was the cylinder door switch. I bent the pins inside the pigtail connector that plugs to the male plug on the door. I don't know why it wasn't making contact. If I remember well everything was working fine when I had replaced the door lock mechanism but since I was using the fob to open the door I didn't realize I had an issue until after I locked myself out of the car when trying to dig myself out after a snow storm in February.