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Intermittent Engine Codes C1241, U0293, U0100, P0A93

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Logan Jensen, Aug 30, 2021.

  1. Logan Jensen

    Logan Jensen Junior Member

    May 10, 2020
    Orem UT
    2005 Prius
    About two weeks ago my engine randomly threw the codes U0293 and U0100, killing the engine and forcing me to coast over to the side of the road. I got it towed to a shop as soon as possible, but they weren't open over the weekend. When they went to look a the car Monday, everything was fine. No engine lights and the car drove normal. I took it home and then later that day while driving the ABS and parking brake light would turn on and it would let a long high pitched beep. Drove the car home, didn't touch it for a day and again the problem went away on its own. Then, about two days ago I was driving it around and the ABS light kept turning on and letting the long beep out again. On my way home, code P0A93 appeared. I then left my car sitting for a couple days again as I got ahold of a friend with a better OBD that could read the ABS problem. Today I checked a bunch of fuses, code P0A93 was still showing, but the ABS light wasn't actively going off though the better OBD was still giving code U0293 and additionally code C1241. After checking all the fuses I thought would be relevant, and cleaning a bit of corrosion on two, the P0A93 code disappeared on its own, but the two ABS codes are still showing. I don't know much about cars and am not sure what else I personally can do to further diagnose the issues and potentially fix them without paying too much at a shop. Any suggestions?
  2. dolj

    dolj Senior Member

    May 14, 2012
    Wellington, New Zealand
    2007 Prius
    P0A93 is set when the inverter cooling is not within limits. The usual suspects are:
    • Wire harness or connector
    • Inverter cooling system - Water pump with the motor assembly
    • Cooling fan motor
    • No. 2 cooling fan motor
    There are 2 INF (or detail) codes associated with this (346, 347) that will focus your attention on either the inverter coolant pump or the cooling fans behind the radiator. The inverter coolant pump fails more often than the radiator fans and its operation can be easily checked by opening the inverter coolant tank (to the right of the inverter) and then putting the car into IG-ON or READY. Shine a flashlight through the side of the tank while you look down the neck of the tank. If you do not observe any movement of the coolant from the front to the back, your inverter coolant pump is not working and should be replaced.

    Inverter Coolant Pump:
    Prius Gen II Inverter 1 Pump.jpg

    When you say you checked the fuses, did you use an ohmmeter or just look at them. If the latter that is not a very reliable way to do it. look for the AM2 fuse and ...

    Prius Gen II Inverter 2 AM2_Fuse.jpg

    ... check it with an ohmmeter to prove it has continuity. If it is blown, disconnect the plug that is indicated in the picture below before replacing the AM2 fuse with a new one.

    Prius Gen II Inverter 3 Power Connector.jpg

    The U0293 and U0100 indicate the Hybrid Vehicle control ECU Lost Communication with the Hybrid Vehicle ECU and the ECM / PCM "A" respectively.

    Before doing any diagnosing check the health of your 12 V battery (located inside the right rear fender under the floor panel). After the car has been off for 2 hours or more, measure the voltage with a voltmeter and if it is less than 12 V charge it up. Ideally, after the battery has been charged up test it with a load tester. Replace the 12 V battery if the load test is unsatisfactory.

    Report back here with your progess.
    SFO and Raytheeagle like this.