Rep Power: 0

I have a 2002 Civic EX I picked up from "a little old lady's estate". 8500 original miles. When I got it had been sitting, duh! There were flat spots on the tires and they had to be replaced. What brings me here is that I had the AC serviced as it wouldn't get cold. Oil change and the A/C work cost me $289. I am not even sure what they did to be honest. Right after that I popped a P1298 and had it reset at the dealer. They said it was likely a fluke from a sticky window or some other electrical device being brought out of "storage" and into use. Fast forward a few months of awesome service and 9000 miles. I now have the following symptoms:
1. No keyless entry
2. No A/C (just fans no cold air)
3. No dome light
4. No intermittent wipers
5. No reminder chime for the headlights
6. Maybe another one or two I have missed

That said just a Google search minus even a reference to Honda Civic will yield "Honda Civic Multiplex Control Unit / Fuse box" as the cause. Additionally with the brake light on I had the code read at Advanced Auto and was again given the P1298.

I say all of this to ask the question after doing the Mode 1 and Mode 2 testing on the MCU do I just order the MCU/Fuse box and an Electronic Load Detection (ELC), check the grounds and alternator bolts and keep an eye out for trouble or do I give the dealer a troubleshooting fee of $100 and still most likely order the parts and keep an eye out?

 
Rep Power: 518

What were the results of these tests?



ELD is a real common problem by itself. The ELD is in the engine compartment fusebox and can be bought separately.
Part # 38255-S5A-003, USA MSRP $31.60. Probably less over the internet.


The MICU (Multiplex Control Unit) is inside the underdash fusebox. That's one you buy the entire fusebox to get.

Keyless/dome/chime: See if it has blown the back up fuse in the engine compartment box.

AC fans run, but no compressor?
Um, IF I'm reading this wiring diagram right, that should not be because of the MICU. The PCM is seeing the AC request signal from the MICU if the fans come on. From here I can't tell you why the compressor does not, that part needs some diagnosis.

 
Rep Power: 511

I think I bought an ELD for like.. 30-something bucks shipped. Took maybe a half hour to replace.

http://www.hondaautomotiveparts.com/...=38255-S5A-003

comes out to 35 and change shipped from Majestic Honda

 
Rep Power: 0

I went ahead and ordered the parts. I saw way too many posts from different forums saying that the MCU was the cause. To answer questions the back up fuse is good. In mode one everything checked out to include the continuity check. That said after checking continuity, the last step in mode one it said the MCU was the culprit. I did mode two just for extras. I had no codes come up (blink cycles in the dome light). That said I used my library card to pull the procedures for the Mode one and two testing and then found a description of the MCU's function in a partial service manual. It specifically states all the faults I am experiencing to include the "HVAC compressor and fan control" are functions of the MCU. While I still have fan I don't get the compressor. Likewise in the same manual I found a process to test the AC by holding down the Recirc and Rear Defog button down while turning the key to the run pos. If no codes blink the AC components are good. I am going to wait until I receive my ELD and MCU as well as my CD copy of the real service manual to give the verdict. I know there is a certain degree of FM (Freakin' Magic) to all electronics so we'll see. I appreciate the feedback and will provide an update in a day or so.

 
Rep Power: 518

It's UFO technology.

 
Rep Power: 0

Ok the new MCU is here. Honda what is with all the plugs to the darn thing. Installed most likely with the dash out. To get them unplugged you feel like you are breaking wires (time will tell) and then trying to get them matched back up to re-install you feel the same way (again time will tell).

 
Rep Power: 308

Would love to get a hold of a junk one and tear it apart... there is a lot of stuff going on in those things.

 
Rep Power: 0

Well the MCU fixed the issues. All circuits are working again. I also replaced the ELD (Electronic Load Detection) in the engine compartment fuse panel. I was going to change the ground wires but I couldn't find them at the local parts store. Their computer said one of the wires was like 56". I am going to buy good wire and connectors and make them this weekend I guess. I am going to take the MCU to work and do some surgery and see if I can find out what happened. Someone on another forum suggested that both the PCM/ECM and the MCU suffer from cold solder joints. I have access to a bench at work to check that if I can get the dang thing open. I will post back with photos if I can.

 
Rep Power: 518

You can get it open......but it's like a can of worms. Hard to put the lid back on it.

It's like 47 layers of bus bar connections and insulators with a small control unit in the middle.