My experience with the P0A93 alarm.

Hello, fellow Prius people and P0A93 alarm enthusiasts. There is a TL;DR at the end.

I have a 2007 Toyota Prius, 163K miles. I have had this car since 2012 and began experiencing the dreaded combination meter issue in 2014-ish. However, it wasn't until 2016-2017 that the issue became more problematic but was "solved" by our trusty unplugging of the 12V. That worked until the beginning of this summer, where the issue was permanent - as in, dashie no workie. I took it apart and replaced the capacitor. Yay! The car has been working great... until August 1st.

On August 1st I got a master warning light (red triangle), malfunction indicator lamp (check engine), and brake system warning lights (yellow). I drove it home, approximately 20 minutes drive. I checked my brake fluid level, it was fine. I unplugged my 12V to see if the issue would resolve and it did not save the brake system warning lights. I reached out to my brother, as he had an OBD2 reader. No codes were shown, which is not shocking as I deleted them when I unplugged the 12V.

My brother thought we should check my oil and it was below the low mark (we replaced it). In the end, we used the entire bottle, which I found odd - however, it does appear the Gen 2 Prius likes to burn oil as it ages. I did not have any issues for several more days until I was driving over 50 mph. All of the lights returned... so this time I bought my own OBD2 reader and I got the aforementioned alarm code. I found PriusChat forums on the topic and checked for turbulent flow... well, I see it moving around in there so Wth? I found the level to be below the low mark, though... without any evidence of an obvious leak. So I bought some of the good "Toyota Super Long Life Coolant" pink drink and topped her up. She drove like a beaut, AC blasting and none of the previous "mugginess" blowing through. Oh, yeah, I forgot the mention that a month or two prior there was this intermittent issue with my AC feeling "muggy." I chalked it up to an aging car and the scorched heat (well over 100 F most of the days).

I should mention that I bought an OEM replacement inverter pump from Toyota when I bought the pink drink. What can I say, I like the hedge my bets. I was driving back to Toyota today to return the >$250 dollar part (yeah, you read that correctly). Guess what, it all comes back! I promptly got off the highway and took the next safest option home all-the-while waiting for the fuse to blow and the car to die - I read this can happen? Then the "mugginess" returned to the AC, I pulled over and thought about my options again. It wasn't a safe area, so I idiotically bet on getting it home. But first, I checked the alarm... guess what, P0A93. Wth? I looked in the reservoir, it was still full of that pink drink. I reset the alarm and finishing driving it home. No other alarms but the mugginess was still present on the AC.

When this alarm occurs, I feel a slight decrease in power - it's the best way to describe it. The Cruise Control also stops functioning. I believe the Cruise Control stops functioning as a safeguard - but please correct me if I am wrong. At no point did I have any other indication that something was going wrong. The pedals did not feel odd, there was no odors, there was no issue braking.

So... my idea is that I have an intermittently failing inverter pump that I can't consistently replicate an alarm for. I still see turbulent flow. I am torn on taking this $250 part of the box and replacing it, just for the issues to persist. So if anybody has any other thoughts before Wednesday let me know! As far as I know, this is the original inverter pump. I haven't been the best at keeping records and doing personal maintenance, but after being screwed on a bad battery from the dealership I have taken the steps to be a good father for my Prius. I was just a stupid kid, forgive me!

P.S.: My brother said I should bleed the coolant, but I hear that's a pain in this nice person and I could introduce air. The level was low, but not low enough that I could see any bare "tank." Surely this isn't a pesky air bubble causing this alarm at high demand times on the car?

TL;DR: I think my inverter pump is intermittently failing at high demand times (>50 mph and AC). There is still turbulent flow when I look after the car has cooled. The level was low, so I topped it up. It worked fine afterwards... for a couple days, even with driving it on "high demand" and no recurrence of P0A93 alarm. Went to return the inverter pump, but it all happened again. The level has not decreased since and there are no obvious signs of a leak. I guess I'll just replace the inverter pump?

 

Aye, aye! I will report back with results.

 

Thank you for your response. This is part of my conundrum with taking out the inverter pump and replacing it with this new one, although it sounds like this part inevitably fails. Mine is definitely not that good, and without a way to reliably replicate this code I don't know if I could safely get it to my brother's to see if his can provide a sub-code. When I went out today after it cooled, I didn't see much turbulent flow when I turned the car on. It definitely seems more diminished than prior? But again, I can't tell if I am just seeing something that was never there or there is definitely no turbulent flow now.

I feel a bit boxed into changing out this part, but I suppose I'd rather change it myself and THEN take it to a mechanic if I still have issues. It strikes me odd that I can't seem to replicate this alarm. But I'm nervous to make a bigger issue by pushing my inverter to the brink.