P3191 and P0A0F/204

Don't over complicate things. Pull the air filter cover and filter off. Have someone do the start sequence for you while you spray starting fluid into the throttle body. See if it will actually run. At least then you'll know if its ignition related, or fuel related. Could be something as simple as no fuel. Don't over complicate it.

 

I seem to remember reading about that, and it was a calibration (after all, it's a pretty easy firmware fix to just wait a bit longer before giving up). Try looking on TIS or NHTSA for TSBs that mention those trouble codes.

 

All the TSBs are on TIS. You can also find them on NHTSA, but I don't expect anything there that's not also on TIS.

 

I would doubt that this is a "calibration fault". I looked at the freezeframe data from post #1 - it suggests that the engine wasn't really running at all.

The A/F and O2 sensors read as "complete fuel cut" lean (ie, those are the readings you might see when the ECM turns off the injectors during high speed decel)

The 4th page shows that the ecu expected around (+) 75 Nm torque from the ICE, but it used (-) 12 Nm (ie, the motor was spinning the ICE, not the other way around.

If you are sure that the fuel pump operates and it has usable gas in the tank, then I'd look at whether the injectors actually open and spray.

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Well, I do vaguely remember seeing a TSB that did refer to P3191 under difficult starting conditions (like very cold weather), and there was a calibration update listed, and IIRC all that was changed in the firmware was a few more seconds were added to the timeout for the cranking attempt. I don't remember the TSB number offhand, sorry to say, nor do I remember for sure if it was for gen 2 or another generation.

But anyway, that seems like a fix for a problem where the engine usually starts, or almost starts in hard conditions, and just needs a few more seconds' grace. But your Techstream captures keep looking like there aren't any signs of life, like the engine is still being cranked (−21 Nm torque) after 13 seconds (think about starting an engine, and count off 13 s on a stopwatch—that's a long time to crank). And I'm not guessing September in LA really counts as "difficult starting conditions".

This doesn't seem to me like the kind of borderline situation where allowing a few more seconds to crank would make it all better. Rather (as a US Robotics modem support guy said to me on the phone once): "sounds broke."

The fuel pump is supposedly running, and the injectors are supposedly being pulsed at 8.96 ms, but the short fuel trim is at +20.3% and the bangity-bangs are not happening.

 

If the engine is running "perfectly", then the upstream A/F sensor reads (around) 3.3V, the downstream O2 reads around 0.6-0.8V (with a healthy - lit off - cat), and short + long fuel trims near 0%.

The freezeframe data still shows "no" fuel getting into the engine. (crazy lean). How about them injectors? Maybe get a fuel pressure gauge installed and see what the pump can produce.

Do you have another Gen2 Prius handy? Easiest way to figure out what's wrong on your broken car is to compare it with "a known good example" from a working car.

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