Well, I'm usually able to figure things out and fix things by sheer force of will and determination but I've decided to take it to Honda and see what they can come up with. I have an appointment at 1:00 on Friday. It'll be $150/hr for diagnostics but it's going to save me at least that if I can drive it for the next 2.5 months instead of waiting for the local tech school. I will update after they look at it.

 

Came to give an update. Honda appointment was on Friday 5/20 the technician is still working on it and trying to find the issue. According to the woman who called me back just now, he found a few blown fuses (unsure which ones) and is still trying to figure out what caused those to blow. I told her that surprised me because I checked every single one with a continuity tester. I will update again when I find out more information.

 

Good luck!

 

So, the technician is apparently very confident that the issue is at that connector I was concerned about. I'm not able to speak with him directly, but I guess he said that the corrosion was to the point of the blue wire barely being seated in the connector. I tested all of the wires for power and continuity, but perhaps when back probing it moved things just enough to get a working result. I did not mention anything about that connector in any details I gave them in the beginning.

I think I should leave it with them for the repair in case it doesn't work, because I'm sure I'd have to pay an additional hour of diagnostic if I did it myself and then had to bring it back. Not to mention the fees for towing it. No word yet on the cost of the connector or wiring harness though.

As I mentioned previously, I had seen a Youtube video with the issues I had, and that connector was corroded and the cause of the issue on that vehicle as well. I feel that spot could really be susceptible to water and debris given the amount of dirt I found it under and the location. The book says it's behind the rear seat, but it's really more under IMHO, and accidentally leaving a window open when it rains, or even spilled liquids in the trunk (I've had this happen with windshield washer fluid before) could be a problem there.

 

As promised, I'm back with the final results! I finally got my car back in this last week. They replaced the corroded connector and the MCM. I can't help but wonder if the initial problem was just the corroded connector and if I somehow messed up the MCM when I was messing with it, but overall I'm still happy with the outcome and that my car is working again.

They said they found fuse 23 under the hood and fuse 62 blown. I checked those fuses before, both with a test light and visually so not sure what happened there. After they replaced the connector the HDS system was able to communicate with the IMA system again and they found code POA3F Motor Rotor Position Sensor Circuit Malfunction. Solution was to replace the MCM. Through Honda, this would have been over $5400 because for some ridiculous reason you have to buy the entire PDU assembly. I told them I could get an MCM on eBay for about $100 and they were happy to install that for me and do the motor stator calibration. They only charged me $272 for the work they did. I'm still glad I went through all of the work I did myself because it helped me to know that I could get the MCM on eBay, and to understand the system and how it all works better.

I have not rechecked my battery tap voltages yet at this time, but the car stays pretty consistently at 5 to 6 bars on the charge indicator, and with normal driving and no AC I'm getting about 43 mpg. CEL has come back on, but I've always had one for a P0420. I will rescan it soon to verify just to be sure though.

 

Thanks for following up. Very glad to hear it. My world view is intact with the MCM being the solution even if for the wrong reasons.

Sounds like you have a good dealership. That's pretty rare. You have a lot of time invested, but your out of pocket costs are quite reasonable.

Concerning your taps, I wouldn't be too worried about them at this point. If you don't get any positive or negative recalibrations, and you're typically in the 4-7 bar range (lower with A/C use is common), you're good.

The moment you get a calibration, it's time for a grid charge.

Concerning the P0420, in most cases, it's a non-issue, but if you notice a decrease in power and mpg, that may indicate your cat is clogging up. Recommend replacement at that time. I replaced one of our '06 with a magnaflow cat at the time. They're pretty spendy, but they're less than the Honda one, and they have a good reputation. There are potentially viable treatments to improve cat performance. Some remove them and literally wash them in a bucket of soapy water. Another technique is to add a moderate amount of acetone to the gas. Both techniques aim to clean the working surface to improve efficiency above the P0420 threshold. If you have the time, it's worth a try.

Lastly, the A/F (upstream) and O2 (downstream) sensors are common failure points. The A/F sensor is absurdly expensive, but the Denso equivalent is a little more reasonable. Downstream is pretty cheap. If you replace your cat, recommend you replace the downstream O2 sensor at a minimum. Actually, probably a good idea to do that first as a failing O2 sensor can trigger a P0420 in some cases.

I got my sensors from RockAuto, and they also have O2 sensor sockets for about $10 last I checked.

 

There is a pretty extensive troubleshooting tree for that combination of codes. Resolution includes wiring repair, MCM update, MCM replacement, BCM update and BCM replacement.

 

I'm back with some questions. Everything seemed to be working great for awhile but then I barely drove the car for about a month and when I started driving it again I was having recalibrations and the IMA light coming on. Each time I started the car it would be off but then come back on after driving it for a little while. I probably let this go on for too long because I didn't really have time to pull the back to grid charge it. Well, a couple of weeks ago we were still having unusually warm weather in WI, I decided I really needed to do it before it got cold. I thought I should cycle the battery this time and so I did, but I messed up on the final discharge and accidentally left the 2 150W bulbs in until they went out and the whole battery was down to like 3.6V! I had been checking it regularly and on the last check it was in the mid 150s--the 2 previous discharges it had still taken hours to get from the mid 150s down to 144V, but on this third one I came out about an hour later and it was down to that extreme low. Well, I did a full grid charge on it to 192V or so, let it rest for a couple of hours before putting it back in the car. Everything seemed great for a couple of hours and i was getting 52 mpg, but then I started getting recals and the IMA light came back on. I tried a 3x 12V reset the next day, it didn't help. The car started doing recals pretty much constantly. I decided to actually check the code and it's the battery deterioration code. I didn't check the codes previously because I was pretty sure I just needed to do another grid charge regardless, so I'm not sure if I was getting that code already before I started the whole process or it if was something else. At one point the 12V battery light came on and I was getting no assist/regen until I turned the car off and started it again. I decided to try one more 24 hour grid charge just in case the extreme discharge caused it to really need a longer charge to balance. I figured this had a slim chance of actually helping but it was worth a shot. I did a 24 hour charge to 192V, then let it rest overnight and it was about 183V. It didn't really help, still getting a lot of recals and IMA light will come on. Most of the subpacks are reading at 17.1 or 17.2. Subpacks 7 and 9 were at 16.9 so those two are clearly problematic. I think 1 other subpack was 17.0.

I know that frequent charging and discharging is hard on the pack, but I wanted to ask given what happened on that 3rd discharge if there was any chance that cycling it again would help, or if that would just make it even worse (as I expect it would). I've been kicking myself so hard for that final screw up, but then also trying to remind myself that this pack is 10 years old and likely already having those issues before my mistake.

Anyway, a new battery is not an option right now. Steve, I have previously seen you post that there are no "new" batteries out there because Sanyo and Panasonic stopped making them. Is this still true or are there companies out there making them aftermarket? I see that Bumble Bee, which I know you highly recommend offers both new and reconditioned batteries, so I was curious about the possibility of purchasing new sticks from overseas to replace at least subpacks 7 and 9.

Also, the car is jerking a lot on acceleration. I'm wondering if the failing battery could be affecting this, as it seems like it wasn't happening as much fresh off the grid charge, then gets worse as time goes on. At times it seems to get really excessive to the point where it's extremely annoying to drive the car, but the next time I go to drive it, it's not as bad. I would say it never goes away completely, but has times where it really acts up if you will. I know it could be related to the P420 I have, among other things, but just wanted to get your thoughts on whether the bad battery could also cause this.

I'm not sure that bypassing the pack is a good option for me because 90% of my driving is stop and go in town, and with my job I'm making a lot of short trips, so I'm turning the car on and off frequently.

 

A deep discharge on a failing pack can convert cells that are mostly working to cells that barely or don't work.

What you're not seeing is that under load, the low subpacks likely drop notably lower than the others.

There are "new" aftermarket cells. They are all made in China.

"new" is not equivalent to "new." Panasonic/Sanyo cells perform differently than the Chinese ones. Often that difference is enough that if you mix them in the same pack, the pack may trigger errors due to the variations on the tap voltages.

Ordering new subpacks from China will almost certainly be a waste of time and money, or simply the start of you having to order and replace another every few months until you've spent more than you would on a replacement pack.

I would personally recommend you pursue a reconditioned pack with Bumblebee.

P0420 typically starts with cat underperformance; however, it can progress to clogging and exhaust restriction. This will rob the car of power and cause increased utilization of the hybrid battery. It may or may not be the source of the jerking.

Many fail to replace spark plugs on schedule, use the wrong plugs, or only do half of them (there are actually 8, 4 in front, 4 in back). NGK and Denso make long life Iridium plugs that last 100-120K miles. This can contribute to jerkiness. If your CEL has flashed, this is an indication of active misfires, and should be fixed immediately. In rare cases, the coils can contribute to this as well.

The HCH2 during a forced charge negative recalibration is completely gutless.

 

I'm pretty sure I have replaced the plugs, but I was planning on asking my mechanic to check them because I can't remember if or exactly when. CEL has not flashed.

Regarding the subpacks, I only briefly Googled it, but it looked like I could order all new sticks for around $1000 from China. A reconditioned pack from Bumblebee will cost me almost $1500 with shipping after the $500 core refund. I do agree that Bumblebee is the best option, but I'm not sure I can come up with the 2 grand to make that happen. Not that I even have $1K right now, LOL, but what are your thoughts on ordering all new sticks from China then? I would have to guess that Bumblebee also orders all of their new sticks from there, though I'm sure they get them in bulk and are therefore able to match them very precisely.