Hi all. Been trying to diagnose a starting problem I've been having with my 2005 Civic EX.

I've been running a scan tool while running that car, and I have noticed that while cruising on the freeway at like 60mph, with engine revs at like 2800 or so, and I get like 11.7 volts from the ecu (no big load other than the radio and the AC on lowest setting).

http://members.***.net/moaltar/screenshot%286%29.jpg

Could this be a problem with the alternator not giving me enough juice? If I turn on the AC full blast and lights, or if I rev above 3000 rpms, the volts will go up to about 13.5.

But when I check the alternator and battery with a volt meter while the engine is on, I can see 14.2 volts.

Anyone know whats going on?

Thanks a bunch.

 

It would be easier for me to just post these two links.

Link 1

Link 2

Hopefully one of our resident techs will chime in, also.

 

Hey, thanks for the good info.

I will start testing these today after work. Even without the test listed here, I suspect that the battery or alternator might both be gone now. Before I got your info today, I turned the high beams on the car (when the engine was off) for about 20sec. Tried to start the car, and it struggled REAL bad.

Also, while driving to work today, with no big load on the engine other than the radio, and cruising under 3000rpm, the voltage from the scan tool was in the 11's.

I guess I'll be replacing something here real soon. And this battery is only a year old too.

 

So, I got the battery and alternator checked by AAA, and they say its good. It was reading 12.59V and 450CCA.

But the alternator was only reading 13.0V and 4.8 amps while loaded. According to the honda service manual, it should be between 13.9 - 15.1V and over 60 amps while loaded. So I think the alternator is toast.

I'm going to swap the battery to a known good one today, just to be sure its ok before I swap the alternator though.

 

It's not your battery because your battery does not make the vehicle run the alternator does

 

-Reviving a very old post-

Making a long story somewhat short, AAA sold me a crappy battery and didnt want to take it back. Replaced with a new Autozone battery. Car ran fine (for a while). Hard starting and misfires started to happen. Cylinder head was pulled and unseated valves and valve guides were found. $1500 later, the 75000mi Civic was running fine. Wife thought car was cursed (it was red). Traded it for a 2010 TSX.

The end.