Unexpected Maintenance Mode

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Chick, Jul 27, 2022.

  1. Chick

    Chick New Member

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    Hello - i am new to posting, although i have threads many threads to find solutions to issues that have popped up on me over the life of my Prius.

    i own a 2nd hand 2007 Prius Touring. I got an OBD2 code reader app to help understand the car.

    i got p1116 & p1121 codes, so i put in a new ICE water pump. That’s all well and good.

    about a year ago my catalytic converter was stolen. Insurance wouldn’t cover the full replacement - so i had to work with an aftermarket cat (new O2 sensor too). Did well for about 8 months - then threw a p0420 code last month. I did a deep dive and started eliminating the least expensive repairs first (i am DIY). I replaced the downstream O2 sensor that was part of the cat repair. Did well for a week and i got the p0420 again.

    This time it also triggered p0a93 (new inverter coolant pump has been ordered. But i checked all fluid levels while i was investigating. Engine oil was very low - filled it back up. ICE coolant was also very low - filled it as well - and did a little “bleeding” to remove any air bubbles just in case (there were a few tiny burps, but not enough to impact performance). Added a fuel cleaner to a tank one pip shy of full. There are no drips or leaks under the car?

    I also “eye balled” the cat and think there may be a bad weld. That i will have to go to a muffler shop to verify/repair.

    So here’s the issue - just did a short test drive, couple miles around the neighborhood at about 25-35 mph. Right as i got a few houses away from home i got the RED TRIANGLE OF DEATH again (p0a93 triggered), got VSC, ((!)), ABS, and Check Engine too (p2238 this time - first time). At this stop sign when the lights triggered - the car also triggered the hand break light, a high pitched noise went off, the car went into Maintenance Mode and the brakes kinda went hard and stopped working normally - this happened all by itself.

    i have deep-dived these but can only find them as isolated issues - not all happening at the same time. Are they related? Is the inverter going bad? Will the inverter water pump take care of this? Not sure where to look next. Any advice is greatly appreciated. Thanks in advance.
     
  2. JC91006

    JC91006 Senior Member

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    You should tackle one problem at a time. The original p1121 code is not really related to a new ICE water pump, it's letting you know the 3 way coolant valve is the problem. When this goes bad, you would get a check engine light.

    P0A93 is a problem with the inverter coolant pump or coolant flow. Most likely pump has failed.

    P0420 is most likely associated with a failed catalytic converter, the aftermarket stuff is not know to be very high quality.

    I think you should address those issues first and see what else remains afterwards
     
  3. mr_guy_mann

    mr_guy_mann Senior Member

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    Press the power button twice (ignition ON mode- dashboard and warning lights lit up). Do you see circulating in the inverter coolant tank? What brand inverter pump did you use before? (OE has the fewest problems). The overheat code is commonly set because of a faulty pump, but can also result from restricted flow (air pocket or a clog) or poor airflow through the bottom 25% of the radiator (the section used to cool the inverter).

    The P2238 indicates something wrong with the upstream Air-Fuel sensor or its wiring. I would look at scan data and see what the sensor is showing once the engine has warmed up some. Normal voltage is around 3.3V but that moves around as you change RPM and load. Can go down to 2.0V at heavy accel, and up to 5.0V when the fuel is cut (engine off or "spinning" above 40mph). If you need a sensor - go OE or Denso from a reputable source (there are problems with online counterfeits).

    Cat code- deal with the AF sensor and ANY possible leaks anywhere near the cat and sensors. Esp. the spring loaded "donut" gasket at the exhaust manifold.

    Don't know about brakes "freaking out" - should have codes in ABS. What are you using to scan with?

    Posted via the PriusChat mobile app.
     
    #3 mr_guy_mann, Jul 29, 2022
    Last edited: Jul 29, 2022
  4. Mendel Leisk

    Mendel Leisk Underfoot

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    You had comprehensive insurance, which covers theft/vandalism? Maybe take them to court?
     
  5. Chick

    Chick New Member

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    Thank you for the replies! Definitely a major help!

    Medel - yes, that cat problem was handled by insurance.

    mr guy mann - i’ve done what you recommend a few times, and everything seems to work out as you describe. I can feel coolant working through the inverter system, but have a new pump for that on order.

    jc19006 - yes, one at a time. I fixed the ICE coolant codes with a new pump for that system. I believe i found a bad weld in the cat which would explain the 420 code.

    but the 0a93 and 2238 codes only popped up in the last few days of repairs. Not a problem to replace the inverter coolant pump - seems like an easier step than a new inverter.

    i guess my real question is - if the inverter pump us failing (not totally failed yet), could the overheated inverter trigger other warning lights due to erratic power?

    i am also now wondering if my ECU computer may be the final problem. It always seems to be ID’d as a potential issue when i read up on all the codes i have gotten.

    To answer a question: i have the Carista OBD2 connector, and use Car Scanner app on my iphone.
     
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