One Headlight/Multiplex Unit Problem: '03 Civic
09-24-2007, 03:25 PM
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One Headlight/Multiplex Unit Problem: '03 Civic
Hello,
2003 Civic EX.
In 2005 (when the car was 2 years old), my driver's side low beam headlight would not function (high beam worked). I ruled out fuses and the bulb itself, and then took it to the dealership mechanic who found that the problem was a faulty Multiplex Unit. I believe this is also referred to as the Multiplex Integrated Control Unit (MICU), and is part of the under-dash fuse box assembly. The mechanic replaced the assembly and this fixed the problem.
Now, again 2 years later, the problem has come back. I've taken it now to a local mechanic who confirmed that the problem again is the Multiplex Unit. He could not point to a source problem other than this.
What is the explanation for this happening again? Is the part inherently prone to this problem? Might there be a root problem that has never been addressed that caused the problem both times? I am resisting bringing it back to the dealer mechanic until I have more information.
Any help is appreciated!
-J
2003 Civic EX.
In 2005 (when the car was 2 years old), my driver's side low beam headlight would not function (high beam worked). I ruled out fuses and the bulb itself, and then took it to the dealership mechanic who found that the problem was a faulty Multiplex Unit. I believe this is also referred to as the Multiplex Integrated Control Unit (MICU), and is part of the under-dash fuse box assembly. The mechanic replaced the assembly and this fixed the problem.
Now, again 2 years later, the problem has come back. I've taken it now to a local mechanic who confirmed that the problem again is the Multiplex Unit. He could not point to a source problem other than this.
What is the explanation for this happening again? Is the part inherently prone to this problem? Might there be a root problem that has never been addressed that caused the problem both times? I am resisting bringing it back to the dealer mechanic until I have more information.
Any help is appreciated!
-J
09-24-2007, 04:49 PM
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Re: One Headlight/Multiplex Unit Problem: '03 Civic (jbond03civic)
I haven't heard of the multiplex unit malfunctioning. For the same problem to happen twice there should be something else causing the multiplex unit to malfunction.
Have you ever left your car for an extended period of time without driving it? Rats could have chewed up a wire causing the multiplex to go bad.
Have you ever left your car for an extended period of time without driving it? Rats could have chewed up a wire causing the multiplex to go bad.
09-24-2007, 06:22 PM
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Re: One Headlight/Multiplex Unit Problem: '03 Civic (jbond03civic)
Stupid question but,is the car an 03? 01-02 Civics within a certain vin range had S/B 04-015. If it is indeed an 03 then the bulletin does not apply.
09-24-2007, 07:05 PM
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Re: One Headlight/Multiplex Unit Problem: '03 Civic (jbond03civic)
If voltage is going into the MICU and not coming out,then its a bad MICU. Why its happening is the question. Can't see any other reason then a bad MICU. Make sure hes looking for faulty or loose pins. Aftermarket alarm?
09-25-2007, 02:09 AM
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Re: One Headlight/Multiplex Unit Problem: '03 Civic (IMALLSLO)
No after market (or any) alarm; the car is pretty much an out-of-the box '03 civic. When you say bad pins, are you referring to the pins on the fuse box assembly or the connectors on it or both?
By the way, I had another random thought: could a faulty relay cause eventual MICU failure? It occurred to me that when I had the fuse box assembly replaced a couple years ago, I don't know that they put in new fuses and relays; I assume they just moved over the ones that were in the old assembly and put them in the new assembly. Could something like a relay be functional enough to work, but faulty enough to cause MICU failure? If not a relay, is there anything else that could potentially be described this way?
By the way, I had another random thought: could a faulty relay cause eventual MICU failure? It occurred to me that when I had the fuse box assembly replaced a couple years ago, I don't know that they put in new fuses and relays; I assume they just moved over the ones that were in the old assembly and put them in the new assembly. Could something like a relay be functional enough to work, but faulty enough to cause MICU failure? If not a relay, is there anything else that could potentially be described this way?
