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The problems:

1. Brake light remains on (On instrument panel)
2. A/C does not get cold
3. Power locks do not work (including the key fob)

Everything else seems to be working fine. All three problems happened at the same time a while ago for one day. The following day, all three problems went away. A couple days after that all three came back and remain till now.

The car was just purchased a couple months ago and the previous owner (a friend) said he never had that problem.

 
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Do you have two fobs? I had an Oldsmobile once that had a problem with an aftermarket remote starter, door lock, security system (eventually it had to be replaced, under warranty). By using the other fob, I delayed the problems for a while. I think the interlock system can really mess you up when it goes amok.
Sometimes, I hate technology.

 
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well the a/c and lock problems both seem like a relay thing.. my guess is that somehow they run off of some circuit thta runs off of the same relay.. because what happenes is that your a/c compressor isn't kicking on, your power lock system isn't working(not necessarily a fuse but maybe) and your e-brake ground isn't getting to the ecu... so idk what the fix would be but it's gonna be something simple more than likely.. so check all fuses and relays..

 
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brake light on might also be that you need to check the level of brake fluid in the reservoir. might be that the level is low and some vehicles have a low level sensor on the reservoir.

 
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Have same problem on 2002 Honda Civic. I looked at the wiring schematics and the this system goes through a Multiplex Control Module that is located behind the under-dash fuse box. Honda says they would have to troubleshoot problem before replacing it. The whole fuse box has to be changed if this is the problem. Fuse box cost $200.

 
Rep Power: 812

1. brake light on may just mean your brake fluid is low.
2. drive the car at a constant speed at 65mph for at least 15 minutes with the a/c running cold at full fan. if it still wont get cold, you may just need a recharge of the refrigerant, or it may be more serious. when you turn the a/c on, do you hear the compressor click on and both radiator fans turn on? could be a simple switch or a busted compressor hard to say.
3. power locks, is it every door not working? do you hear any noise when you try to lock them from the inside with the lock button?

 
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I have a 2002 civic with the same problem. Also the dome light does not work when the doors are opened. The dome light will come on in the on position on the light itself. Everything worked fine yesterday. I have checked fuses inside and under the hood.

 
Rep Power: 308

The dome light is also part of the multiplex that is contained inside of the under dash box. The box is all plugs and wires, If you take your time it would be an easy change. The procedure for the box is on the site.

 
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I just encountered these three problems all at once yesterday. Did you fix yours at Honda dealership? May I know how much did the dealership charge you to fix it? Thank you very much.

 
Rep Power: 812

prolly cheaper to get one from junkyard and swap it in yourself.

 
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this is a "chronic" problem with Hondas. with "friends" like these, who needs enemies?

 
Rep Power: 308

Honda does seem to have chosen some poor electronics "modules" at times (multiplex,SRS control,DRL)

In this day and age of electronics you should not have failures of solid state devices.

 
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I have the same problem with my 2001 Civic Ex. Also my dome light doesn't work with the doors and the keychime and headlight warning tone doesn't work as well. Have you resolved the problem ? Was it the multiplex control module ?

 
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Do you guys have a picture or step on how to replace the Miltiplex control unit?

 
Rep Power: 234

1. Disconnect batt- then batt+

2. Wait AT LEAST 3 minutes (This gives the SRS system capacitor time to dissipate so you don't blow your airbags)

3. Remove both covers under steering wheel (driver's dash lower cover and driver's dash under cover respectively)

4. Fuse box is under central portion of dash. Locate and disconnect all connectors on the side facing you.

5. Disconnect this bolt:

6. Slide fuse box down out of bracket

7. Disconnect all connectors on the back side

8. Do it all in reverse

*NOTE: The SRS connectors (always yellow, you can't miss 'em) have a spring loaded sleeve. To disconnect: pull on the sleeve (not the connector). To reconnect: push on the connector (not the sleeve)

I just used the SRS connector on the side of the steering column as an example. You can see the under-dash fuse box in the left side of the frame. My finger is on the sleeve portion that I'm talking about:

PS: You can get a used one for $50-75 here: http://www.car-part.com/

 
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I am having the exact same issue today with my 2002 Honda CR V. Brake light on, AC blowing hot and door locks stopped working simultaniously. Looks like fuses blew but it is still running. Think it maybe the fuse box or mulitplex but not sure. Searching for others that have the same problem.

 
Rep Power: 308

I would imagine the CR V system is very similar to the one used in the Civics. Sounds like the multiplex.

As far as a replacement... I would get a new part, one from the junkyard might be problem as well.

Order by year & trim level to be safe.

 
Rep Power: 0

My 2002 honda civic ex is having exactly the same problem!!!! Brake light stays on, power door doesn't work and AC won't blow cold. And all just happened all of a sudden.
Man, can you tell me if you have got your problem fixed? How did you do it? Did you fix yourself or did you take it to a mechanic? WHich parts were replaced? How much did they charge you? Any further info will be highly appreciated.
Thank you so much!!!

 
Rep Power: 0

My 2002 honda civic ex is having exactly the same problem!!!! Brake light stays on, power door doesn't work and AC won't blow cold. And all just happened all of a sudden.
Man, can you tell me if you have got your problem fixed? How did you do it? Did you fix yourself or did you take it to a mechanic? WHich parts were replaced? How much did they charge you?
Thank you so much!!!

 
Rep Power: 0

My 2002 honda civic ex is having exactly the same problem!!!! Brake light stays on, power door doesn't work and AC won't blow cold. And all just happened all of a sudden.
can everybody tell me if you have got the same problem fixed? How did you do it? Did you fix yourself or did you take it to a mechanic? WHich parts were replaced? How much did they charge you?
Thank you so much!!!

 
Rep Power: 0

It definetly is the MCU. Check out this site also. http://www.question-defense.com/2010...brake-light-on - I changed mine today - about 30 min and it fixed all the problems:
1- A/C
2- power door locks
3- dome light not working with doot, but will turn on with switch
4- auto wipers not working when you pull to spray/clean
5-chime not working

Part is 38200-S5A-A31. It is 155 + S and H (About 167 total at honda parts now . com. Found alittle cheaper at some other site, just do a web search.

 
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Very helpful website indeed. Thanks a lot. Actually I already got that probelm fixed with the help of another person from civicforums.com. I purchased a new fuse box for $150 and replaced myself. I took me about 30 min and it was not that easy job really, especially you have to pull out all those plugs in such limited space under the dashboard.

 
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I have read a few threads on door lock issues and none of them explain exactly what is happening with my driver side door. I was wondering if some of you might post what you think is the problem with my door lock. I would really appreciate it.

Here what is happening with my 2003 honda civic (DXG Sedan)

1-My 4 yr kid got the remote and Lock/Unlock the car door non stop.
2-By the time i noticed,none of the car door work with remote.
3-My driver side and all 3 passenger side doors are not lock and unlock via remote but i can still hear the sound of relay get activated seems like they working fine.
4-None of the fuse has blowned
5-Door can be lock and unlock by the key from outside.
6-Manual internal locking button at the driver side activate relays but door still not lock or unlock
7-what i noticed is if i try locking the door through the lock/unlok switch from the driver side then my left indicator light comes on and both indicator and emergency light stopped working.Then i have to turned my car off to get my right side indicator work only. Left indicator never works since i got this door problem and if i tried left indicator a relay chattering sounds appeared some where from the fuse box.

Is anybody having the same issue.
Appreciate your feedback.

 
Rep Power: 812

it looks like he overheated the actuator motors. they were only designed for a couple of uses at a time, not continuous opening and closing. even a few times will start to heat them up, like the window motors. if you keep doing it, they will get hot enough to fail.

the only thing that phsyically opens the lock is the actuator motor. so if you are hearing a noise, that means it is getting power but is unable to push up the lock.

 
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Bought a used 01 sedan EX. im having the same problem with the locks. the brake light is off, the ac idk about since i havent used it to cold in NY and i never use the ac. The guy i bought it from said the ac needs a recharge.

Anyone else having the TRIP A and B reset also each time you turn the car on and off?

 
Rep Power: 0

TO ALL THATS DEFINITELY THE PROBLEM, THE MCU IS BAD, THE ONLY WAY TO FIX IS TO REPLACE THE FUSSE ASSEMBLY BOX. I FIXED MINE LIKE THAT, AND HAVE A NEW FUSE BOX FOR SALE EMAIL ME@ elchulow@gmail.com

ONLY OF THIS IS YOUR FUSE ASSEMBLY NUMBER
38200-S5P-A11
WHICH IS FOR A 2011 HONDA CIVIX LX, MANUAL TRANSMISSION, 2 DOOR

YOU CANNOT PUT A DIFFRENT ONE ON IT, SOME FUNCTIONS WILL WORK AND SOME WONT, SO DONT HALF *** IT TRYING TO PUT ONE FROM A DIFFERENT MODEL CAR...
SAVE YOURSELVES A HEADACHE...

 
Rep Power: 0

Hi, Thanks for the help, My 2001 civic sedan GL (Australia) had the same issues:

Central Lock not working
Interior lights not working
Door open indicator not working
Seat belts not fasten warning lights not working
Wiper int (only) not working
Air Con not working
Head Lights on warning buzzer not working
Park Brake warning lights stays on

Replace the Multiplex Control Unit, somehow the model number is different from America & Australia, but still got it when I describe the part. Bought used one because it cost me $195, and Brand new ones $532 (everything is expensive in Australia)

Took me more than 30 mins to remove and replace the unit, lets just say I'm getting old and not as flexible as I used to be, otherwise its actually quite easy to replace.

Everything worked... so far... Fitted it yesterday and drove the car today, some warning lights stop working again ( maybe because I bought a used item?) will continue to use the car everyday and see how it goes. at least aircon & central locks works now.

 
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My 2001 Civic had the exact problem with dash brake light and power locks and replacing the MCU fixed that. (Very much a PITA procedure for me as I am 6'4" with large hands). However, when I went to drive it out of the garage I discovered the shift release doesn't work. (foot on brake is supposed to activate solenoid). I probably damaged a wire due to my difficulties with the very confined work area under the dash. Can anyone identify which connector provides this feed? Can I just remove this lockout feature if I have to? Most importantly, is anyone aware of any more important function that may have been impacted as well? Thank you for sharing the knowledge!

 
Rep Power: 308

You will want to check the brake lights operation.

Use the shifter release provided.

 
Rep Power: 0

Hi! Okay so, my check engine light is on and has been on for a little over a month. I took it to Advance Auto for them to plug my car up to their handy machine an tell me whats wrong but the tool would not connect. The guy mentioned something about a fuse but did not go into detail. Also, my battery tends to die on me. This has happened 3 times in the course of a month and a half. The battery was replaced with a new/used battery and the mechanic stated that my alternator is fine. What could be causing this problem?