2004 civic hybrid 12v battery light
 

Hey All! Finally got a handle here. I've had this civic for about 2 years now. Traded my motorcycle for it, and it's been a lot of ups and downs. The ima light has always been on. About a year ago, I started having to replace stuff on it.

I've replaced the 12v battery (2017), ignition coils, plugs, fuel injectors and starter as well as some of the front end linkage. Car has 375k on it now. When the ima system would stop charging the cell, I did the road start/stop ignition test and got it to start working again. Now, when the car idles, the 12v light has been coming on and sometimes kills the car. This is an issue it's had in the past as well. I'm trying to troubleshoot it because it rides great now when things are working properly. It's a manual trans btw.

Re: 2004 civic hybrid 12v battery light
 

Rev and hold 2K rpm for 30 seconds. Does the 12V light go out?

Re: 2004 civic hybrid 12v battery light
 

Holy crap that is a lot of miles! Hard to believe this model car got that far without several bearings being replaced and probably an engine rebuild or replacement. No CVT would ever last that long, but lucky for you, your car doesn't have one.

Anyway, the red 12V light you are seeing at stops typically means the IMA is really truly toast. When a pack reaches that point grid charging won't usually help. Often you won't see any charge/boost lights while driving, and the SOC may be zero. Your options are either to replace the IMA or to bypass it. The latter might be considered an illegal modification to the emissions system though, depending where you live, which might mean that you cannot renew the registration when it comes up.

Re: 2004 civic hybrid 12v battery light
 

I haven't had to do that yet. So far it just goes on while I'm on the highway and then I flip the ignition and it goes off.

it's been off all day today though.

Re: 2004 civic hybrid 12v battery light
 

The cell is boosting and charging just fine, which despite the mileage makes me want to say that it's still functional. It still goes to full charge and discharge.

what about a fuse or this dc to dc converter thing I keep hearing about? What about the cooling fan or an associated sensor?

Re: 2004 civic hybrid 12v battery light
 

Assuming the IMA light is on due to the battery, a bad IMA battery can prevent consistent 12V charging. They tend to get progressively worse and you will eventually only charge between about 1600 and 3500 rpm and in some cases, 12V charging may be completely disabled until you bypass the pack.

When the IMA light returns, you should either blink the codes or at least have them read, so you know what you're dealing with.

Unlikely you have an issue with a fuse or your DC-DC. Your situation is very typical of 12V charging performance when the battery has tripped an IMA light.

I suspect the ignition cycle thing simply causes a surge of current that helps boost the pack voltage above the error threshold and permits normal function. As time passes, and it gets used, the battery gets more imbalanced, and you eventually code again.

Re: 2004 civic hybrid 12v battery light
 

Ok, I agree with you because it makes sense now.

I found a cell out of a 2004 with 113k on it. No ima light on the seller's civic. What are the chances of this battery breathing life back into my car for another 50 to 100k?? I talked him down to $200 on it. Is it worth a go?

Re: 2004 civic hybrid 12v battery light
 

What is a "cell"? Do you mean the whole IMA pack or just one stick? Assuming the former that seems like a reasonable amount to spend if only to have a second pack to mess about with. With two packs you could test all the sticks in that new pack, swap it for the one currently in your car, test all the sticks in that pack, all the while having a car to drive. You may find that between the two of them you have enough good sticks to build a fully functioning pack. (But I wouldn't bet on it.) On the other hand, $200 is way too much for a single stick.

Also, why is that person selling the pack (assuming it is a pack)? If the Civic is still running and he's keeping it that would suggest the pack isn't so hot. Still, $200 is roughly the core charge for an IMA if you buy a new battery, so the price is OK.

Re: 2004 civic hybrid 12v battery light
 

No I meant the whole pack... like the big box you take out and put in next to the converter. That's what he's selling for 200 bucks.

That being said, I'd like to rebuild the one I take out and make it new. How much is that?