Multiplex Control Unit
06-16-2012
#32
Registered!!
Join Date: Jun 2012
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 
Re: Multiplex Control UNit
Did more trouble shooting tonight with my multimeter. Each mini fuse tested just fine. I visually checked the large fuses under the hood. I printed out the wire diagrams I received from Craig and will look those over tonight and highlight trouble areas.
The things not working:
Car audio- has constant memory power but no ACC power from ignition
Auto Locks- Do Not work key in or key out KeyFOB does not work to lock/unlock
Tripometer- Does not keep memory
Dome Lights- Do not work with open door with key out of ignition, Work with open door with key in ignition. Works fine manually.
Chime reminder for lights on/key in ignition is NOT working
*airbag light is on
*cruise control operates perfectly.
So it seems to be that the car audio is the only ACC ignition problem wire that I have. The rest are all constant power wires.
I've done dozens of stereo installs and had a fuse pop from time to time. Nothing major like this has ever happened. I'm determined to find a solution without going to a dealership. I'll get by with a little help from my friends!
Thanks guys and gals out there!
The things not working:
Car audio- has constant memory power but no ACC power from ignition
Auto Locks- Do Not work key in or key out KeyFOB does not work to lock/unlock
Tripometer- Does not keep memory
Dome Lights- Do not work with open door with key out of ignition, Work with open door with key in ignition. Works fine manually.
Chime reminder for lights on/key in ignition is NOT working
*airbag light is on
*cruise control operates perfectly.
So it seems to be that the car audio is the only ACC ignition problem wire that I have. The rest are all constant power wires.
I've done dozens of stereo installs and had a fuse pop from time to time. Nothing major like this has ever happened. I'm determined to find a solution without going to a dealership. I'll get by with a little help from my friends!
Thanks guys and gals out there!
06-16-2012
#33
If you think a good mechanic is expensive, try hiring a bad one
Re: Multiplex Control UNit
I'm gonna pick a not very random thing I think I would check:
Car audio- has constant memory power but no ACC power from ignition
So, you checked and fuse #8 in the underdash box HAS power when checked on the little tabs on top of the fuse.....in ACC and RUN key positions, right?
(This fuse also supplies power to the MICU, through internal circuits in the fusebox.)
But there is no power on this same wire (A2) at the radio?
So...how far does the power from that fuse go? Check a few of the other connectors that circuit runs through...
You know what backprobing is? You need it now.
In the wire diagram for the radio, that circuit comes out of the fusebox at terminal N2, yel/red wire...IS THERE B+there (at the same time that fuse gets power)?
(you will need a diagram of all the large fusebox connectors)
Power at terminal N2: Yes or no?
NO would mean the box has an open circuit that is internal. Junk the box.
YES would mean you got a wiring problem elsewhere.
N2 is also connected to fusebox terminals E2, Q7, and V2. Power at any of those? Power missing at all those? (probably all irrelevant, but what the H)
Auto Locks- Do Not work key in or key out KeyFOB does not work to lock/unlock
Tripometer- Does not keep memory
Dome Lights- Do not work with open door with key out of ignition, Work with open door with key in ignition. Works fine manually.
Chime reminder for lights on/key in ignition is NOT working
Honestly, not sure what to think about these without a lot more research. Most of it sounds like the MICU is no longer doing all that it's supposed to do.
The check at N2 is my first check. If it fails that, then it gets fixed first and see if all the rest of this comes back to life.
*airbag light is on
Was it on before you got into this radio mess? Or is this just since the radio mess?
Check for codes?
*cruise control operates perfectly.
I guess we don't need to care about that then.
So it seems to be that the car audio is the only ACC ignition problem wire that I have. The rest are all constant power wires.
Not really constant power wires.
All that other stuff may be operated through the MICU.
Warning beeper, seat belt light + SRS, dome lights, and power locks. If the MICU computer can't work, all that stuff goes down, or operates with minimum functions.
No clue on the tripmeter. Never noticed that one.
There are communication lines between several control units (MICU-gauges-PCM-SRS-ABS-?), and one unit goes down, all units may be affected in some way.
HTH
Car audio- has constant memory power but no ACC power from ignition
So, you checked and fuse #8 in the underdash box HAS power when checked on the little tabs on top of the fuse.....in ACC and RUN key positions, right?
(This fuse also supplies power to the MICU, through internal circuits in the fusebox.)
But there is no power on this same wire (A2) at the radio?
So...how far does the power from that fuse go? Check a few of the other connectors that circuit runs through...
You know what backprobing is? You need it now.
In the wire diagram for the radio, that circuit comes out of the fusebox at terminal N2, yel/red wire...IS THERE B+there (at the same time that fuse gets power)?
(you will need a diagram of all the large fusebox connectors)
Power at terminal N2: Yes or no?
NO would mean the box has an open circuit that is internal. Junk the box.
YES would mean you got a wiring problem elsewhere.
N2 is also connected to fusebox terminals E2, Q7, and V2. Power at any of those? Power missing at all those? (probably all irrelevant, but what the H)
Auto Locks- Do Not work key in or key out KeyFOB does not work to lock/unlock
Tripometer- Does not keep memory
Dome Lights- Do not work with open door with key out of ignition, Work with open door with key in ignition. Works fine manually.
Chime reminder for lights on/key in ignition is NOT working
Honestly, not sure what to think about these without a lot more research. Most of it sounds like the MICU is no longer doing all that it's supposed to do.
The check at N2 is my first check. If it fails that, then it gets fixed first and see if all the rest of this comes back to life.
*airbag light is on
Was it on before you got into this radio mess? Or is this just since the radio mess?
Check for codes?
*cruise control operates perfectly.
I guess we don't need to care about that then.
So it seems to be that the car audio is the only ACC ignition problem wire that I have. The rest are all constant power wires.
Not really constant power wires.
All that other stuff may be operated through the MICU.
Warning beeper, seat belt light + SRS, dome lights, and power locks. If the MICU computer can't work, all that stuff goes down, or operates with minimum functions.
No clue on the tripmeter. Never noticed that one.
There are communication lines between several control units (MICU-gauges-PCM-SRS-ABS-?), and one unit goes down, all units may be affected in some way.
HTH
06-20-2012
#34
Registered!!
Join Date: Jun 2012
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control UNit
Would it be possible that i also have a bad mcu?
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
The car itself did not come with a keyless remote but its suppose to have one. The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on. And when he tried to bypass it it cancels itself out and doesn't want to work.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
The radio works, but its an aftermarket radio. I am not sure if the wipers worked, it hasn't rained all that much to use it. The ebrake light does not come on either when the ebrake is disengaged.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
The car itself did not come with a keyless remote but its suppose to have one. The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on. And when he tried to bypass it it cancels itself out and doesn't want to work.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
The radio works, but its an aftermarket radio. I am not sure if the wipers worked, it hasn't rained all that much to use it. The ebrake light does not come on either when the ebrake is disengaged.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Last edited by mad_vtak; 06-20-2012 at 12:28 PM. Reason: spelling
06-20-2012
#35
If you think a good mechanic is expensive, try hiring a bad one
Re: Multiplex Control UNit
Would it be possible that i also have a bad mcu?
Maybe.
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
What else has been hacked then?
Probably every part of the car that was ever touched by that person.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
How does THIS work?
No part of the AC runs through the trunk.
**shakes head**
The car itself did not come with a keyless remote but its suppose to have one.
Is it EQUIPPED with keyless? LX would have had a dealer installed accessory kit IIRC.
The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on.
And when he tried to bypass it it cancels itself out and doesn't want to work.
Good possibility that person is in too far over their head.
Not everyone is good with electricity.
It is like the "Final Frontier" of auto repair.
Not many ever get to be truly good at it.
Does this shop/person have a dealer level scanner?
Access to proper information that would tell about test procedures for the cluster and the MICU?
Letting the wrong people work on it could cause you more problems that it should have ever had.It sounds like you may be headed that direction already.
Sadly, many dealers also employ the same caliber of people in far too high of a ratio.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
May or may not be part of the problem.
Test.
I am not sure if the wipers worked, it hasn't rained all that much to use it.
Rain is not needed to test the wipers.
The ebrake light does not come on either when the ebrake is disengaged.
Again,
May or may not be part of the problem.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
No idea without some real troubleshooting.
I want to know what the computers all say about this.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
All lights become "AUTO OFF" sooner or later, as you found out..
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Kinda sounds like your car may have multiple problems, only one of which may be the MICU.
There isn't an easy answer, and you really need a brain surgeon doing the electrical work, not a knuckle dragging parts changer. (Does that draw a mental picture, or what?)
HTH
Maybe.
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
What else has been hacked then?
Probably every part of the car that was ever touched by that person.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
How does THIS work?
No part of the AC runs through the trunk.
**shakes head**
The car itself did not come with a keyless remote but its suppose to have one.
Is it EQUIPPED with keyless? LX would have had a dealer installed accessory kit IIRC.
The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on.
And when he tried to bypass it it cancels itself out and doesn't want to work.
Good possibility that person is in too far over their head.
Not everyone is good with electricity.
It is like the "Final Frontier" of auto repair.
Not many ever get to be truly good at it.
Does this shop/person have a dealer level scanner?
Access to proper information that would tell about test procedures for the cluster and the MICU?
Letting the wrong people work on it could cause you more problems that it should have ever had.It sounds like you may be headed that direction already.
Sadly, many dealers also employ the same caliber of people in far too high of a ratio.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
May or may not be part of the problem.
Test.
I am not sure if the wipers worked, it hasn't rained all that much to use it.
Rain is not needed to test the wipers.
The ebrake light does not come on either when the ebrake is disengaged.
Again,
May or may not be part of the problem.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
No idea without some real troubleshooting.
I want to know what the computers all say about this.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
All lights become "AUTO OFF" sooner or later, as you found out..
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Kinda sounds like your car may have multiple problems, only one of which may be the MICU.
There isn't an easy answer, and you really need a brain surgeon doing the electrical work, not a knuckle dragging parts changer. (Does that draw a mental picture, or what?)
HTH
06-21-2012
#36
Registered!!
Join Date: Jun 2012
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control UNit
Would it be possible that i also have a bad mcu?
Maybe.
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
What else has been hacked then?
Probably every part of the car that was ever touched by that person.
I would like to take it to honda for them to look at, but not pay an arm and leg for them to just check it over.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
How does THIS work?
No part of the AC runs through the trunk.
**shakes head**
Yeah, i was just trying to draw a picture of how they botched it up.
The car itself did not come with a keyless remote but its suppose to have one.
Is it EQUIPPED with keyless? LX would have had a dealer installed accessory kit IIRC.
I assume there would be keyless, did that year not come out with it?
The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on.
And when he tried to bypass it it cancels itself out and doesn't want to work.
Good possibility that person is in too far over their head.
Not everyone is good with electricity.
It is like the "Final Frontier" of auto repair.
Not many ever get to be truly good at it.
Does this shop/person have a dealer level scanner?
Access to proper information that would tell about test procedures for the cluster and the MICU?
i understand, he just took a voltage meter and read where the signal died
Letting the wrong people work on it could cause you more problems that it should have ever had.It sounds like you may be headed that direction already.
Sadly, many dealers also employ the same caliber of people in far too high of a ratio.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
May or may not be part of the problem.
Test.
I am not sure if the wipers worked, it hasn't rained all that much to use it.
Rain is not needed to test the wipers.
The ebrake light does not come on either when the ebrake is disengaged.
Again,
May or may not be part of the problem.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
No idea without some real troubleshooting.
I want to know what the computers all say about this.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
All lights become "AUTO OFF" sooner or later, as you found out..
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Kinda sounds like your car may have multiple problems, only one of which may be the MICU.
There isn't an easy answer, and you really need a brain surgeon doing the electrical work, not a knuckle dragging parts changer. (Does that draw a mental picture, or what?)
HTH
Maybe.
Issues:
No ac
No power door locks
Speedo is off by 10mph
Bought the car from an auction and after the car was purchased it was found that who ever own this car previously botched the wiring for the ac.
What else has been hacked then?
Probably every part of the car that was ever touched by that person.
I would like to take it to honda for them to look at, but not pay an arm and leg for them to just check it over.
The the trunk you can see the wiring where the previous owner tried to fix the ac themselves.
How does THIS work?
No part of the AC runs through the trunk.
**shakes head**
Yeah, i was just trying to draw a picture of how they botched it up.
The car itself did not come with a keyless remote but its suppose to have one.
Is it EQUIPPED with keyless? LX would have had a dealer installed accessory kit IIRC.
I assume there would be keyless, did that year not come out with it?
The car currently is sitting in a shop where they found that all the volt signal drops at the MCU. He got a way to have the fans turn on but the condenser does not come on.
And when he tried to bypass it it cancels itself out and doesn't want to work.
Good possibility that person is in too far over their head.
Not everyone is good with electricity.
It is like the "Final Frontier" of auto repair.
Not many ever get to be truly good at it.
Does this shop/person have a dealer level scanner?
Access to proper information that would tell about test procedures for the cluster and the MICU?
i understand, he just took a voltage meter and read where the signal died
Letting the wrong people work on it could cause you more problems that it should have ever had.It sounds like you may be headed that direction already.
Sadly, many dealers also employ the same caliber of people in far too high of a ratio.
As far the the door locks, you have to manually unlock the doors with a key and cannot use the switch that is on the door.
May or may not be part of the problem.
Test.
I am not sure if the wipers worked, it hasn't rained all that much to use it.
Rain is not needed to test the wipers.
The ebrake light does not come on either when the ebrake is disengaged.
Again,
May or may not be part of the problem.
Another issue is that the speedo is off by 10mph. The moment you turn on the car you are already going 10MPH.
No idea without some real troubleshooting.
I want to know what the computers all say about this.
When the car was first purchased, the headlights were accidentally left on. Does a 2002 Civic LX model have a headlight buzzer or anything to kill the lights if the lights were accidentally left on?
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
All lights become "AUTO OFF" sooner or later, as you found out..
I apologize for the long post but i posted this same thing on Honda-Tech and no one helped, i see this was an old post that has been bumped and been getting responses.
Kinda sounds like your car may have multiple problems, only one of which may be the MICU.
There isn't an easy answer, and you really need a brain surgeon doing the electrical work, not a knuckle dragging parts changer. (Does that draw a mental picture, or what?)
HTH
I found a MICU for 80 bucks and they have a 30 day return policy, if it doesnt work i can always return it.
06-21-2012
#37
If you think a good mechanic is expensive, try hiring a bad one
Re: Multiplex Control UNit
[quote=ezone;4606800]
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
I have a 01 DX in the bay right now, it has NO chimes at all.
AFAIK, EX and LX have the chimes.
I believe it has ONLY a warning chime, and is controlled through the MICU and the cluster.
I have a 01 DX in the bay right now, it has NO chimes at all.
AFAIK, EX and LX have the chimes.
06-30-2012
#38
Registered!!
Join Date: Jun 2012
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control Unit
+1 on the knuckle dragging parts changer LMAO! I just took mine to a honda-tech who does some work on the side. Some of the wires were mysteriously not conductive after back probing. He did a patch on the wire harness. Took him a bit of time to get enough slack to do the soldering. Everything works well. Still used the new fuse box. I didn't mind paying the laborer directly to have a peace of mind!
02-26-2013
#40
Registered!!
Join Date: Feb 2013
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control Unit
Craig W: I am hoping you may be able to help us solve the issues with our daughter's 2002 Honda Civic Ex (2-door, auto). We bought the car used about a year ago. When we bought it, we were not given the keyless entry remotes but Honda keys because the power door locks did not work. Once we had the car for a bit, we noticed the interior dome light only came on when switched on manually and the door chime never activated when the key was in the ignition and either the driver's side or passenger door were open. The dome light, however, will occasionally come on when the passenger side door is open but this is not at all routine or a regular occurrence.
Our local Honda dealership suggested I replace the driver's side switch assembly (Part 35400S5A013), which signals whether the door is open or closed. The technician was confident the broken switch explained why the door chime and dome light weren't working. He also thought replacing the switch could restore the power door locks, which he thought could be receiving a signal that the doors are always open. This was a simple process and required only a $6 part. Interestingly, the original switch was disconnected, but when we replaced the part with the new one, nothing changed. The door chime and dome light still do not come on when the door is opened. The power door locks still don't work. The passenger's side door switch is not broken, but most of the time does not activate the dome light when the door is open.
The dealership insists that the MCU is not the problem. They say the break lights and A/C would not be functioning if the issue was with the MCU.
What are your thoughts? Could it be a backup fuse? If so, where is that located?
Here are some other interesting issues with this car. The previous owner replaced an aftermarket radio that was installed in the car when he bought it because of a "short" in the radio. The new radio works but the not all the speakers in the car work. The SLS light has been reset but came back on and stayed on.
You had corresponded online with the person below (Mr. Doyle) who had similar issues. A new MCU is priced at nearly $400. I'm reluctant to replace that part if the issue is elsewhere. The dealership suggested replacing the door lock actuators, but I'm doubting that is the source of the problem. Any information you can provide would be much appreciated. Thank you.
#24 (permalink)
Mr. Doyle
Registered!!
2004 Honda Civic
Join Date: Jun 2012
Posts: 6
Points: 243, Level: 4
Level up: 86%, 7 Points needed
Activity: 0%
iTrader: (0)
Rep Power: 0
Re: Multiplex Control UNit
Just checked. All large fuse block are still intact. When I plugged in the new fuse panel, i had the aftermarket cd player installed. Wiring seemed fine. I there a special way that I need to wire in the aftermarket cd player?
Strange thing is, that I only have a few signs of a bad MCU.
My power locks do not work
Reminder does not work
Radio does not work
Dome light upon door entry does not work
Dome light works with key in the on position and doors open
Things that differ from most posts.
A/C does work great
Intermittent wipers work
Our local Honda dealership suggested I replace the driver's side switch assembly (Part 35400S5A013), which signals whether the door is open or closed. The technician was confident the broken switch explained why the door chime and dome light weren't working. He also thought replacing the switch could restore the power door locks, which he thought could be receiving a signal that the doors are always open. This was a simple process and required only a $6 part. Interestingly, the original switch was disconnected, but when we replaced the part with the new one, nothing changed. The door chime and dome light still do not come on when the door is opened. The power door locks still don't work. The passenger's side door switch is not broken, but most of the time does not activate the dome light when the door is open.
The dealership insists that the MCU is not the problem. They say the break lights and A/C would not be functioning if the issue was with the MCU.
What are your thoughts? Could it be a backup fuse? If so, where is that located?
Here are some other interesting issues with this car. The previous owner replaced an aftermarket radio that was installed in the car when he bought it because of a "short" in the radio. The new radio works but the not all the speakers in the car work. The SLS light has been reset but came back on and stayed on.
You had corresponded online with the person below (Mr. Doyle) who had similar issues. A new MCU is priced at nearly $400. I'm reluctant to replace that part if the issue is elsewhere. The dealership suggested replacing the door lock actuators, but I'm doubting that is the source of the problem. Any information you can provide would be much appreciated. Thank you.
#24 (permalink)
Mr. Doyle
Registered!!
2004 Honda Civic
Join Date: Jun 2012
Posts: 6
Points: 243, Level: 4
Level up: 86%, 7 Points needed
Activity: 0%
iTrader: (0)
Rep Power: 0
Re: Multiplex Control UNit
Just checked. All large fuse block are still intact. When I plugged in the new fuse panel, i had the aftermarket cd player installed. Wiring seemed fine. I there a special way that I need to wire in the aftermarket cd player?
Strange thing is, that I only have a few signs of a bad MCU.
My power locks do not work
Reminder does not work
Radio does not work
Dome light upon door entry does not work
Dome light works with key in the on position and doors open
Things that differ from most posts.
A/C does work great
Intermittent wipers work
02-26-2013
#41
Re: Multiplex Control Unit
^^^^ Not sure if I got a diagnosis from Mr Doyle or not....sent him electrical information. There have been bad micu units...but really should be checked 100% before ruling though.
If backup fuse open, items work with key at II iirc.
Some CRV owners have had no warnings, no dome w/drivers door and driver jamb switch is fine.
Any sound at all when attempting power locks ?
If backup fuse open, items work with key at II iirc.
Some CRV owners have had no warnings, no dome w/drivers door and driver jamb switch is fine.
Any sound at all when attempting power locks ?
02-26-2013
#42
Registered!!
Join Date: Feb 2013
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control Unit
No, there is no sound when you attempt to open or close the locks with the interior switch. I talked to the dealership again today and they are suggesting a $228 electrical system test, which they say can determine if the Multiplex Control Unit is faulty or if the issue could be traced to the after-market radio. The radio is an interesting part of the equation since the original radio was replaced by Car Toys in April 2009 with a higher-end Kenwood system, which then was replaced by the next owner of the car with a low-end Kenwood radio in August 2011. The higher-end radio supposedly had a short. However, new keys were cut for the car by the dealership in Aug. 2008, which makes me believe the problems with the keyless entry system predate the radio replacements. The dealership says the radio has a significant role in the operation of the door locks, SRS light and other aspects of the electrical system. They say improper replacement of radios often causes a host of other problems...The dealership says when the original radio is replaced, a installer such as Car Toys often pushes the original radio back into the dash rather than removes it so there is a chance the original radio could be hiding behind the replacement radio...
02-26-2013
#44
If you think a good mechanic is expensive, try hiring a bad one
Re: Multiplex Control Unit
The way I see it, about the only things an installer can short out are the 2 power feeds, and the "illumination" circuit, which might take out the dash lights and could damage the instrument cluster.
02-26-2013
#46
If you think a good mechanic is expensive, try hiring a bad one
Re: Multiplex Control Unit
If you follow Hondas service procedures, disconnecting the battery is the first step in a very large number of jobs.
02-27-2013
#47
Registered!!
iTrader: (18)
Join Date: Oct 2004
Posts: 1,252
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 
Re: Multiplex Control Unit
even when installing the oem radio where all you have to do is plug in the blue plug? (the question was asked with the installation of an aftermarket radio in mind though)
01-14-2016
#48
Registered!!
Join Date: Jan 2016
Age: 50
Posts: 1
Likes: 0
Received 0 Likes
on
0 Posts
Rep Power: 0 Re: Multiplex Control Unit
There have also been issues with the under hood fuse box. Auto dealerships are saying that it is the high dollar MCU, when the problem is actually the fuse box that is under the hood. Check out the link below.
These guys seem to have several different models of the fuse boxes in stock, and have some knowledge on them.
http://www.autopartscheaper.com/2004...50-s5a-a03.htm
These guys seem to have several different models of the fuse boxes in stock, and have some knowledge on them.
http://www.autopartscheaper.com/2004...50-s5a-a03.htm
Thread
Thread Starter
Honda Civic Forum
Replies
Last Post
Dangerousjordan
Mechanical Problems/Vehicle Issues and Fix-it Forum
6
07-30-2015 11:19 AM
robbie374
Electrical, Wiring, and In Car Entertainment
4
07-07-2015 02:56 AM
