One other thing, and I'm not trying to be condescending... Is your oil level properly between the two marks on the dipstick? I had an HCH2 that would not indicate low oil pressure, but it was very low on oil, and it behaved like it had a rev limiter around 3000rpm. This was when I first bought it. Two fresh quarts of oil from the parts store got me into the proper range on the dipstick, and the "rev limiter" disappeared.

 

Yes, when I start the car and let it idle for around 30 to 60 seconds the battery light comes on
If I rev to 2200 RPM the battery light does disappear yes

(I can't get the car to rev past around 2700 RPM for some reason, not sure)

 

When the HV battery is inop or bypassed, the DC-DC converter can't charge the 12V system throughout the rpm range. Below about 1600rpm, the IMA motor output voltage is too low to be converted. Above about 3500rpm, the voltage is too high to be converted.

The behavior you observed indicates your DC-DC converter is working, and it can charge your 12V in the appropriate range. When 12V battery light is on, you are NOT charging 12V. When 12V battery light is off, you are charging 12V.

Oil level?

 

Yes, the 12V charging and battery light thing make total sense, thank you.

As far as oil level, I am ashamed and will take my lumps. It was very low. Just didn't think to check it.
It's now quite full, but unfortunately the problem remains. I turn the car on, wait 10 seconds, then rev, the first time I can get to around 2900 before motor starts shaking again and RPMs slow down of their own accord to below 2000... then subsequent attempts to rev do not get up to 2900 but more like 2600, then 2400, then 2400, etc.

 

"Full" = in the proper range on the dipstick?

Is your CEL illuminated? I'm starting to think the A/F sensor error may be the issue here.

 

Yes sir, slightly over the proper range on dipstick. Checked it three times.
CEL is indeed on.

 

I'm inclined to use a code reader to confirm blink code 41. There are different diagnostic procedures for P0134 and P0135.

'm fairly certain your symptoms could be explained by a faulty A/F sensor. Also worth checking if any wires have been chewed through by rodents or if anything is disconnected.

 

A few days ago the code reader at O'Reilly read P0135. ​​​​​​​maybe upstream? That's what the O'R computer seems to suggest for that

 

Yes. P0134 is typically resolved simply by replacing the A/F sensor. P0135 requires checking various voltage and continuities because it may indicate a broken or shorted wire. If your car sat, and rodents got hold of it, you may be dealing with nibbled wires. However, it can be resolved by replacing the A/F sensor.

Worth checking:

No 14 OPTION 40A fuse under hood fuse/relay box
No 4 FI-ECU 10A fuse in the under dash fuse/relay box
No 2 LAF (A/F) HEATER 20A fuse in the under dash fuse/relay box

The first two are unlikely, but the third may be contributing.

 

All those fuses are still good.
I went ahead and replaced the O2 sensor - https://www.oreillyauto.com/detail/c...r/den1/2349005
It was a perfect fit here, easily reached - https://www.civicforums.com/forums/3...0135-code.html

However, while the engine stall is not as pronounced, it still is stalling and the car is basically unusable with that stall in place.
Any other ideas would be much appreciated.