2006 FEH. I reset the PCM after a repair to the hybrid battery (fan replacement). Immediately began running rough on startup but would improve when warmed up. But it would randomly stall (red triangle of death, stop safely now, no ice power, but still electric power). It grew worse over time and eventually it set codes: P1000-FF, P1A0C-FF, P2195-P, P0300, P0302, and P0304.

After reading the forums, I concluded that the PCM had forgotten its throttle body compensation strategy, so I cleaned the throttle body. It immediately ran better, except that it would still threaten to stall during idle - specifically when it would move to battery charging mode. It was also more likely to actually stall if there were other accessories on (i.e. the ac). Once warmed up it ran fine. It also ran fine if I kept my foot lightly on the gas during idle so that the rpms stayed up around 2200. I warmed it up, ran it in defrost for 10 minutes to help it relearn the throttle, but it never solved the problem. It would run fine after it was warm (likely completely warm - after being on for 20 or 30 minutes), but I had problems with it any time it idled during the first 20 minutes or so of driving (unless it was in park and my foot was on the gas). Also, shifting it into neutral during the first 20 minutes would almost instantly kill it. Ice dead, stop safely now, no electric power either. Putting my foot on the gas did not solve this (although I think that the computer doesn't actually give it much more gas when it's in neutral).

I replaced the O2 sensor and the spark plugs. No change. I then replaced the throttle body with a new one. Immediate improvement - now it can often run without stalling if it's in park and you're idling. But while it's warming up it still stalls while driving when your foot comes off the gas, and it almost instantly stalls if you're sitting and shift into neutral. Also it again threw code P2195 - O2 sensor biased lean (but this is a new O2 sensor)

What is different about park and neutral such that if you're sitting idling in either, and the engine is cold, it stalls almost instantly in neutral, but not in park? And why, even in park, does it periodically have a bit of difficulty maintaining idle when the battery moves to charging mode?

I assume that when the engine is cold its either not getting enough fuel, or it's getting too much O2 - and so when you're in park and the battery shifts to charging, it has trouble compensating for the new load, and that whatever is different about park and neutral, if you shift to neutral it utterly fails to either provide enough fuel or it provides way too much O2? I imagine that's why it stalls when it's cold and I'm driving - because when you're in Drive and your foot is off the gas, the engine is effectively in neutral, not in park?

Why did cleaning the throttle body help, and replacing the throttle body help more if it's a fuel problem? And why did none of these problems begin until I reset the pcm?

I'd appreciate any advice - I'm somewhat at wit's end.

 

lso it again threw code P2195 - O2 sensor biased lean (but this is a new O2 sensor)


You have a vacuum leak somewhere. I think a big one. I got that code when I was playing with the vacuum for the brake.

 

The vacuum leak idea made a ton of sense to me, but I couldn't find it and I took it to a local mechanic and he couldn't find it either. He says that he thinks it's a software issue and that I need to bring it to the dealer (which is a long way, unfortunately).

Any more thoughts?