Lately, my brake light stays lit on the dashboard even though the emergency brake is not in use, the electric door locks do not work, but you can open and lock the doors with the key, the dome light does not go on. The lights on sensor does not buzz when you open the door with the key in. The fan comes on but the airconditioner does not blow cold air. This happens intermittently. My mechanic cannot figure out what the problem is. What gives?

 

Hi, disclaimer, I don't have a wiring diagram for your car so this is all a guess.

I'll assume you've checked system voltage and looked at the underhood grounds.

With that many symptoms I'd start looking for a common denominator. It could be a bad ground, but that would not account for the dome light not getting power.

I'd suspect the integrated control unit (ICU) which I think is the Multiplex Integrated Control Unit (MICU) in your car. Probably it is attached to your fuse panel, and probably it's a ***** to get at and remove. Check the underdash grounds between episodes of cursing. HINT, sometimes it's easier to remove the driver's seat than it is to work around it, often there is cash or better to be found under a seat!

With the MICU out it's on to bad joints, not the good type that, hopefully, you found under the seat, but the electrical type.

Probably you can open the MICU, remove the circuit board and find bad solder joints.
look at http://softsolder.wordpress.com/2009...solder-joints/ pay attention to the image labeled "joint number two." and the drawing of "solder thermal stress"

this one show an obvious solder failure
http://www.vcoa.org/700-900-faq/Imag...ointCracks.gif


Anyway, the solder joint cracks will be very subtle, redo any that look the least bit suspect. Remelt 'em and add a tiny bit of fine gauge rosin core solder from an electronics store with a low wattage pencil type soldering iron. NOT a soldering gun. Look for bad connections around transistors and at external connections in particular. Practice on a dead radio or your neighbor's car first.

Fixing bad solder is the key to fixing intermittent electronic failures in all sorts of things. The rule is when whacking stuff no longer restores correct function it's time to look for the bad connections.

I've had 100% success resoldering honda boards.
Of course you could just slap in a new MICU, but that would be cheating.

Bear in mind the more you spend, the less likely I am to be correct, you've been warned!

Or it could be a bad fuse somewhere..

let me know how it works out

 

Check the brake fluid level, that will cause the light to come on, and if it keeps leaking out, brake failure. I think the BRAKE light circuit doesn't have anything to do with the multiplex control unit. But as the other guy noted, the keyless, dome light, and air conditioner all depend on it.

 

If it is like civicalized said and it's your ICU, check under the hood for a blown fuse because usually components of the ICU with other things relies on one fuse

 

I agree.

OP: Check whether hood 10A fuse 9 or dash 7.5A fuse 10 is blown. If those are fine, run the mode 1 and mode 2 tests on the MCU.

 

I will pass alll of this advice on to my mechanic who seems to be stumped. Thanks.

 

i am having the exact same issue. what did your mechanic tell you? how much did you cost?

 

My mechanic didn't want to touch it and recommended that I take the car to a local shop that specializes in electrical problems. I am scheduled to have the work done on Thursday, so I'll know more then. Once I get an answer I'll post the results.

 

I ended up taking the car to a shop that specializes in weird electrical problems. It took them a couple of days to identify the problem because it was intermittent, and of course, the car worked perfectly for them. It was a bad ICU. The cost of a new part, just under $200, 4 hours of labor $220, total with tax about $440.

 

Because you rely completely on mechanics to fix even simple car problems, you'll never know whether you paid $440 to replace a blown fuse, tighten a loose connector, or replace a bad MCU.