new IMA battery, recognized by car, but not charging?

[rpearson]

idle for 10 seconds: on
hold 2000 rpm 10 sec & 4000 rpm: off

I drove it for an hour (~40 mi) to the dealer this afternoon and dropped it off for my appt next Monday (it worked out better for my schedule to just drop it off today). The car performed fine, not too bad even going up the long grade into Santa Fe. Now that I tihnk about it, I wonder how I managed to keep it at 65 without IMA assist. I used to do that commute every single day and the car didn't always manage that.

I'll ask the dealer to check out the 12V battery & replace it if needed. The battery is old, really old. I don't remember the last time it was replaced. And it sat for a year. And before that it was getting drained all the time while the IMA battery was on its final legs. so yeah. probably not the healthiest battery ever.

my husband wants to mention that the voltage across the 12V battery dropped when the motor was running. from 12 point something to 11.5.

[rpearson]

OK, the dealer says 12 volt battery is good. They are saying they need to open everything up to debug the error code P1639, so I'm going to have a shop that is certified to work on Honda hybrids debug it instead (presumably it will save me some $$). Especially since the dealer didn't actually have a good idea as to what the problem was. I had the feeling they've never really seen this code before.

[S Keith]

Your description that the battery is old, sat for over a year, etc., puts the dealer's statement in question. Unless somebody put an actual load tester on the battery, no one can say it's good. If you let a battery sit in a car for a year, it will be completely flat. If that battery has any age or wear on it previously, it's capacity and CCA will be dramatically reduced due to sulfation from storage at low SoC. I suspect the mechanic used the HDS to read the voltage, saw it was okay and never bothered to cross the shop, grab a load tester and actually load the battery. A voltage check is only part of the picture.

The charge light behavior indicates your 12V charging system is operating above idle.

I assume the drop to 11.5V was at idle. Did you check voltage at 2000rpm when the red light was out?

I am not at all convinced that your 12V is good.

Did you look for a missing fuse?

P1639 Code in 2003 HCH? - GreenHybrid - Hybrid Cars

[rpearson]

I'm going to ask them to look for a missing fuse & load test if they didn't. When I went to that thread you linked to, I wondered how I missed reading about the outcome, then realized you asked them. thanks!

[S Keith]

Just trying to help.

Steve

[rpearson]

So, they checked the fuses before I guess, and they are fine. And they did do a load test when they checked the battery. I'll take it to the other shop and let them have at it.

[rpearson]

I am rpearson's husband. Don't want to confuse.

I went to auto zone and told them I wanted to replace the battery although I didn't actually believe it was bad. They said take it out of the car and we'll stick it on our charger/tester and you'll know for sure. An hour later they called and said the 12 volt was fine.

In all this I also found a bad IMA fuse in the fuse bank under the hood. Replaced it. I haven't measured any voltages since replacing the burnt fuse.

I'm not really sure what is going on. The 12 volt seems to be charging as the car never fails to start. We've driven it maybe 200 miles without incident.

The only thing I am certain of is that we get the error code P1639 and that the IMA charge/assist lights don't come on.

I've reset the error codes several times and P1639 returns within 10 seconds or so. My wife and son think the car is actually receiving assist from the IMA system. I'm not sure about that. The charge/assist light comes on when the ignition is first energized but then goes off. I guess there is a moment where it says it is charging at 3 bars for a few seconds when the car is first started and then it goes off and stays off. Tomorrow I plan to put the old IMA battery back in and read the error codes with it. Then put the new IMA battery back in.

How do you replace the red IMA light? It seems that would be an additional diagnostic that would be good to have. What does the MOTD do?

[S Keith]

Originally Posted by rpearson

I am rpearson's husband. Don't want to confuse.

I went to auto zone and told them I wanted to replace the battery although I didn't actually believe it was bad. They said take it out of the car and we'll stick it on our charger/tester and you'll know for sure. An hour later they called and said the 12 volt was fine.

In all this I also found a bad IMA fuse in the fuse bank under the hood. Replaced it. I haven't measured any voltages since replacing the burnt fuse.

I'm not really sure what is going on. The 12 volt seems to be charging as the car never fails to start. We've driven it maybe 200 miles without incident.

The only thing I am certain of is that we get the error code P1639 and that the IMA charge/assist lights don't come on.

I've reset the error codes several times and P1639 returns within 10 seconds or so. My wife and son think the car is actually receiving assist from the IMA system. I'm not sure about that. The charge/assist light comes on when the ignition is first energized but then goes off. I guess there is a moment where it says it is charging at 3 bars for a few seconds when the car is first started and then it goes off and stays off. Tomorrow I plan to put the old IMA battery back in and read the error codes with it. Then put the new IMA battery back in.

How do you replace the red IMA light? It seems that would be an additional diagnostic that would be good to have. What does the MOTD do?

If the 12V light is on, 12V charging inop. If it's off, the 12V is charging. Your wife confirmed is it on at idle but off at 2000rpm. This means the DC-Dc converter is working w/o the IMA battery. It's charging the 12V based on its input. Idle output of the IMA motor is too low, between about 1500 and 3500, it's good, 3500+ is too high.

Your wife linked to a thread on Greenhybrid where someone had the same code. It was a missing fuse.

The next diagnostic in that thread was to swap out the MCM (one of the boxes in the IMA cavity with the battery) with a used unit.

Unfortunately, I don't have a service manual for HCH1. The HCH1 is closer to the Insight than the HCH2. The Insight mentioned a P1638 code relating to the MCM, but the HCH2 has nothing close.

The diagnostic for the Insight is to reset the MCM via the #18 Back Up Fuse (under dash) or the Honda Diagnostic System. It does not indicate that a 12V reset would do it, but I'd be surprised if it didn't. If that doesn't correct it, replace MCM with a known working unit.

Probably a good idea to confirm you get the same codes with the old pack. If you don't, you can try to swap the junction boards between the packs. It's pretty easy. If you go that route, be careful, there's 90V or so exposed when the junction board's off. Do NOT touch more than one of the Aluminum spacers at once.

Don't know how to replace the IMA light. Likely have to access the back of the cluster.

You might consider a service manual of your own:

2003 2004 Honda Civic Hybrid Shop Service Repair Manual CD Engine Drivetrain | eBay

My HCH2 manual is from that source ("Bishko", not that seller), and I've been very happy with it.

Good luck,

Steve

[rpearson]

The MCM was the first thing they replaced. Then they swapped their new MCM for an ECM and finally they said it was neither the the MCM or ECM but a missing fuse. I did find a bad fuse in the engine compartment but it did not solve the problem. I also removed and checked a fuse under the dash that I thought was for the IMA but I should probably check that I pulled the correct one.

I've ordered the shop manual and the electronic trouble shooting guide. I'm not optimistic that they'll help a shade tree mechanic but it's worth a shot. I gave up shade tree mechanic-ing a quarter century ago but this IMA stuff is pricey. I don't trust the dealer to get it right without spending more than the car is worth so I'm giving it a whirl. Back in the good old days I always liked Haynes manuals. Do they go into debugging the IMA system?

[S Keith]

I'm with you, but in my mid-40s, I'm still at turning wrenches.

The Honda manuals are pretty good. There's a section dedicated to the IMA, and there's troubleshooting for each code.