Car PCM problem

JON2713

MEMBER
2016 HONDA CIVIC
2.0L
AUTOMATIC
43,000 MILES

Hello,

Recently I bought the car listed above, then a month later I kept getting this error message "check charge system" which has to do with my alternator. I took it to a mechanic and got it replaced. After that I noticed when I went over 4 RPM in the car the same message pops up again but goes away after a day. Mind you this only showed up when my alternator was bad and the car wouldn't start. So recently it shut off on me and wouldn't start again for another day or two. So I quickly took it to Advanced Auto to get the alternator, battery, and car checked. Both the battery and alternator was good but there were 2 error codes I got U0100 and U0038. I researched and it said I need a new PCM(U0100) and another costly repair(U0038). MY question is, should I take it to Honda and pay for the Diagnostic and possibly a new PCM, pay for a licensed mechanic diagnostic (to save money) or should I just reset my PCM in the fuse box?

3 Replies

AL514

MECHANIC
4,692 POSTS

Hello thanks for using 2CarPros. This code is a lose of communication between the ECM and other modules, a CAN BUS communication error. You can try resetting the ECM, but most likely this is a wiring issue or a bad ECM. But if it is a bad ECM, finding out what caused the ECM to go bad in the first place is extremely important. Or the new ECM could fail because of the same problem ie a short to ground, or other power failure somewhere. This is a tough one to diagnose. It may have been a short in the old bad alternator that caused the ECM to fail as well.

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Wednesday, October 23rd, 2019 AT 10:05 AM

JON2713

MEMBER
2 POSTS

Thank you for the reply. Should I take it to Honda or pay local mechanic to figure it out?

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Wednesday, October 23rd, 2019 AT 10:09 AM

AL514

MECHANIC
4,692 POSTS

Well if you have a mechanic that's good enough to know to look for the cause of an ECM failure first. You don't want to just throw a new computer in the car, just to have it fail a week later. ECM's can be costly. I had a Civic with a no communication error once and it ended up being a tiny cut in a wire under the intake manifold. Almost impossible to find, just as an example. If you do take it to Honda, make sure you explain the alternator situation in full so they know the cause of an ECM failure may have been fixed by the new alternator. I'm sorry for your issue, these are difficult situations.

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Thursday, October 24th, 2019 AT 7:04 AM