Hello Everyone,

I was hoping someone or some of you could help me fix my DTC codes and the IMA system on my Civic.

2 weeks ago I purchased a 2003 Honda Civic Hybrid Manual Transmission with 178k miles on it. The previous owner wanted to upgrade in a new car instead of trying to fix it. So I took on the challenge and paid next to nothing for it.

The previous owner had taken the car to the Honda Dealership when the IMA light, Battery light, and CEL were all present. The Honda dealer said P1166, P1435, P1570, and P1600/P1601 were all present. On the paperwork it reads "followed protocal and recommends replacing MCM unit and rechecking." That's it for all those codes also on the same paperwork. The previous owner had replaced the 12v battery with a Napa battery 2 weeks prior. This was all in late Feb/Early March of this year. So the IMA battery and system has not been working since.

So I bought a new upstream O2 sensor. Replaced it and that made the P1166 code go away. Then I charged the 12v aux battery. I also purchased a grid charger harness from Jeff @ Hybrid Automotive.

I was aiming at fixing the rest of the codes with a solid grid charge/balance, then dishcarge to 96v, then recharge, then discharge to 60v, then charge, then dishcarge to 12v then full charge. I let it rest for a hour or two after this. Disconnected the 12v battery so the car could see the new charge.

I started the car and the IMA light comes on automatically without attempting to charge the battery at all. Before the reconditioning process, it would attempt to charge the battery with 3 green bars for a few seconds, then IMA light + CEL would come on. Now it doesn't attempt to charge it at all, just pops the IMA light and CEL right away.

I started to drive the car. The aux battery light comes on at idle, but once above 1300 RPMS or so, the light goes away. So while I was driving, the battery gauge for the IMA system suddenly started to climb all the way to the top. After a few moments of it showing a full charge, it started to slowly fall to the all the way to the bottom. The IMA light and the CEL were still on and never went off. So I pulled over, unhooked the 12v battery to reset system. Waited a few moments and repeated the process all over again. This time after more driving and 20 mins or so later again, the IMA SOC suddenly started to register again out of no where and goes to the top of SOC again. So after a few mins of this, I reset the CEL/IMA light by clearing the codes with Torque and a bluetooth OBDII reader. The IMA light and CEL came back right away and the SOC meter on the IMA guage fell to two bars SOC and stayed there. Still IMA light and CEL on the whole time. Can't get them to go away unless I clear em and they come right back before the clearing process is even done.

All the codes are gone except P1570 and P1600. I don't know if I have a bad IMA battery (bad cells with too much IR) or if I just need a new MCM.

Anyone have any ideas? I was hoping Peter or S Keith or another guru would know what I should/can do. I would like to get this car working correctly with the IMA system. At the same time, I don't want to replace stuff that isn't needed. How would I know if it's the battery or the MCM that is the problem? I've read and scoured the internet for a solution, but at this point I am stuck.

 

99.9% probability it is the battery.

Your car has a lot of miles on it - it is unlikely that that is the original IMA battery. The replacement IMAs that Honda would install when the originals failed under warranty were not new batteries, but rebuilt ones cobbled together out of cells from other packs. These warranty packs were even less reliable than the originals. Guess how I know. So you either have an incredibly old original IMA or a crappy replacement pack. Buy a new IMA pack and all should be well.

At least until the CVT blows up.

 

The battery is reading 172v after 24 hours of charging and 5 hours of resting after the charge.

So how would I guarantee what you say is true? I don't want to go a bad battery route if it's the MCM... Is there a way to check to make sure?

 

That strikes me as a little high actually. It doesn't tell you all that much though. These things tend to fail because the sticks get way out of balance and also because they develop large internal resistances, not because they won't charge to the full voltage.

Sure, you could borrow a known good IMA pack from somebody.

You could also poke around on the stick voltage wires with a voltmeter to see if all the sticks have the same voltage.

I suppose MCMs must fail occasionally, although the only recollection I have, and it is a vague one, of anybody on the boards reporting that was associated with some sort of electrical mishap when futzing around with the IMA pack. NiMH batteries on the other hand do fail. Always, after a long enough period of use.

Unless you have reason to believe that that IMA pack is a recent replacement unit from a reliable vendor (ie, Bumblebee, not Honda) your working hypothesis should be that it is the pack.

 

IIRC P1570 is individual voltage input issue. You likely have a cell on one stick that has excessive self-discharge.

Check your tap voltages by probing the back of the connector with it plugged into the BCM:



Check pins 10+ hours after termination of grid charge:
14-6
6-13
13-5
5-4
1-7
7-2
2-8
8-3
3-9
9-10

Record to 2 decimal places. Take your high voltage and subtract 0.3V. Anything below that number has a bad stick in that pair. Anything below high voltage minus 0.2V is likely marginal, but will work with continued grid charging.

You likely have one or more of those voltages well outside the group by 1V or more.

Steve

 

Thanks. So when I find the problem sticks, I can then replace them with reconditioned ones right? I understand I can replace them, charge /balance and it should be good? I just want to make sure that's what the next step would be.

 

Yes, they can be replaced (if you can find reliable replacements), but it usually becomes a game of whack-a-mole from this point forward because reconditioned IMA sticks are notoriously unreliable. Your use of the HA grid charger will help minimize the frequency of replacement.

Once we confirm an issue at the voltage taps, there are other things we can do to more aggressively check which sticks should be replaced.

Steve

 

So I grid charged for 20 hours, then unplugged the charger. That was last night at 6:30pm pst. So It's been 14 hours or so and I just tested the the connector as you suggested. Here's what I found.

14-6 = 16.59
6-13= 16.54
13-5=16.53
5-4= 16.58
1-7= 16.54
7-2= 16.53
2-8=16.57
8-3= 16.56
3-9= 16.57
9-10= 16.55

Total = 165.56

I then tested the pack at the Hybrid Automotive Plug in the trunk (all of the sticks in series from the harness) and I got the same (165.56) as well.

They seem pretty good right? I just grabbed the codes again, and still 1570 and 1600.

What do you guys think?

 

Did you reset the 12V to clear the codes and see if it returns?

Those are very nice resting voltages.

 

Yes, I unplugged the 12v, still same codes. P1570 and P1600. Do you think it's my MCM? How would I check that?