Is it worth saving? P0A0F code!

Good news is that transmission isn’t destroyed the bad news is that your hv battery and head gasket may have gone bad. If you’re lucky, you’ll have about $6,000 in a rainy day prius fund for repairs.

 

Did disabling the EGR cooler consist of disconnecting the connector?
Then perhaps the valve jammed due to a dirty channel and the EGR channel is still partially open.
In this case, the battery discharge is a consequence of unsuccessful attempts to start the rattling engine.

 

What’s the miles?

 

Hoo boy, that freeze frame puzzled me for a sec. I was startled to see a negative MG2 RPM with the speed of the car shown as 7 MPH. But further down the freeze frame it does show Shift Sensor Shift Pos: R (for all five of the recorded attempts), so I guess the car was legitimately going backwards, and I guess the Vehicle Spd MPH just shows the absolute value.

The trouble code P0A0F in general is just the power management control ECU complaining that the engine hasn't started when asked, and the reason will usually be a more-specific code stored by the ECM.

But a P0A0F with INF code 238 is a verry special one, even shown on a different page in the repair manual from the other P0A0F INF codes. It would mean something about the engine or the transmission input has seized and can't be turned, or has let go (like a broken input shaft) so the transmission end spins freely without the engine crankshaft turning.

Looking at the −3 freeze frame, MG2 was turning −782 rpm and MG1 773 rpm. The MG2 reduction gear is 58:22 so the PSD ring was turning −297 rpm. The input shaft was therefore turning (mg1 + 2.6 ring)/3.6 rpm, which matches (within the fuzz of OBD-II rounded numbers) the zero rpm of the engine. So this looks more like a case of something that can't turn, rather than the input shaft spinning freely.

The other freeze frames look pretty similar, but the rightmost (1) freeze frame seems to show a noticeably lower MG1 rpm, let's see how that looks. I can barely make out the MG2 rpm in that screenshot but I'm calling it −864 (chime in if you can read it better than I can). It can't be too far different from the −782 reading, given as they both go with a vehicle speed rounded to 7 MPH. If MG2 is doing −864 then the PSD ring is doing −328.

But the MG1 rpm in that freeze frame is just 573 rpm. The input shaft doing (mg1 + 2.6 ring)/3.6 would be around −78 rpm, a number that Should Never Happen. It's different from the reported engine rpm of zero, so there is a busted connection somewhere (and if there weren't, it would be cranking the engine backward, which is just another flavor of Should Never Happen).

So I've changed my mind and I think there is a break in the vicinity of the transmission input shaft, and not just something seized. The other freeze frames show the transmission input rpm near zero, corresponding to the engine rpm, but that rightmost freeze frame doesn't. If something were merely seized, I'd expect those rpms to match every time.

(However, Techstream gets all these values for the ECU by sending requests and getting replies, and the values aren't always from the exact same instant, which can make interpretation tricky).

I see that the "Target Engine Rev" is zero in all five records—which is odd for a start attempt, where the target is typically 1100 rpm or so. I'm thinking these freeze frames were saved once the ECU had already decided to set P0A0F-238 and impose its fail-safe behavior of trying to keep the input shaft rpm at zero to avoid doing more damage.

The first thing I'd check next is just the old reach in past the passenger front wheel (with the car off!) and try to turn the crankshaft by hand, and see how that feels.

 

This attachment lists part numbers for the Toyota Gasket Kit (includes head gasket, and everything else you'll encounter, and is OEM, not "this'll fit"), Head Bolts (worth replacing, just to play it safe), and pistons/rings (if you end up doing those).

 

I somehow managed to finish my post without seeing your later one showing the #4 intake port full of coolant.

I would hazard from that photo that the #4 cylinder is also full of coolant, and that when you go to turn the engine by hand, it won't turn. Coolant doesn't play along when squeezed the way air does.

The P0A0F-238 may just mean that the engine couldn't be cranked and the ECU gave up trying, or it could mean the tranny input shaft broke while trying to crank the engine and then the ECU gave up trying.

Looks like head removal is indicated anyway. Once the head is off, you might even be able to (move a lot of stuff carefully out of the way, unplug the fuel pump, have someone hold your beer, and) try to READY the car just briefly, see if the tranny is able to crank the headless engine. (Oil will squirt everywhere.) That would tell you if the input shaft's intact or not, without having to separate the engine and tranny.

 

I believe the PO303 is a misfire for #3. And while excelerating the check engine light
flashes….. I just had this issue. Mine was the #4 spark plug.
Replace the spark plugs, with NON ebay/amazon plugs. Go to Toyota or autozone,
the bosch plugs are pretty good!

 

I should have scrolled down and read more posts…..
Certainly a blown head gasket. You’ll need to check the pistons height’s and make sure
they are all equal, if not, a rod is bent. And check to make sure the head is not warped.

 

I would check all head interfaces for compliance with the flatness specs, only consider machining if they’re outside of spec. See last link on my signature for the specs. (On a phone turn it landscape to see signatures)

 

You’re welcome.
With that much water in their, there is a high possibility of more damage.
A valve might of been bent.
Take your time and check everything. Depending on the amount of damage,
a remanufactured full engine from the hybrid pit would be a good option.

 

Is the car already refusing to crank because the battery is too low (P3000-389), or are you just leery of getting it that low?

A quick test twirl with no compression shouldn't take very much more charge off.

 

This is were you wave the white flag and get a new head gasket plus a new battery. Saving gas cost a lot of money.