2012 gen 3 head gasket repair. P0016 and cannot clear "check hybrid system. Maintenance required"

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Louhazosc, Jul 17, 2025 at 10:29 PM.

Tags:
  1. Louhazosc

    Louhazosc New Member

    Joined:
    May 17, 2025
    3
    0
    0
    Location:
    Maine, USA
    Vehicle:
    2012 Prius
    Model:
    One
    Hey guys,

    Did a head gasket repair. Everything went fine except the one thing I didn't like was every time I'd go to put the tensioner in, it would release before being seated. After a few attempts and pressure i got the bolts on but it was fully released.

    I had the engine set to top dead center, timing marks lined up etc.

    Did a hard reset disconnecting the battery and orange plug. Wife drove it today for 60 miles with no issue. then got a P0016 code - cam and crankshaft not aligned. So I replaced both the cam and crankshaft sensor cause I did hit the valve cover with some brake fluid. Also cleaned the MAF sensor while I was there.

    Now we have nothing. It continues to say "check hybrid system. Maintenance required" Did another hard reset. Battery disconnected, plug out. No good. It actually rattled for a few seconds and immediately shut down. No idea what the rough rattle was.

    So....do I go back in and start over? I really just don't wanna take all that apart and see the timing chain is just fine. Lot of work but I will. Can't think of anything else.

    Also had an issue with our fixd code reader so wasn't able to clear the p0016.

    Im lost at this point

    extra info: 200k miles. Car was sitting for 7 months. New tank of gas. head was machined and cleaned and valves resurfaced. New water pump, thermostat, timing chain, tensioner (but released as stated), cleaned egr, air intakes, new orings...all the things you do on a head gasket.
     
    #1 Louhazosc, Jul 17, 2025 at 10:29 PM
  2. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    12,240
    2,158
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    What is it the timing folks around correct every like 9 turns or someting like that so move crank from timing marks lined up until they come round lined up again ? How many turns ? Or does it align ?
     
    #2 Tombukt2, Jul 18, 2025 at 6:34 AM
  3. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    12,240
    2,158
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    I have the timing code right now on gen 2 it's 500K and chain in sure stretched. Oh well . On our gen3 we had no issue with chain popping out pin at install that I know of.
     
    #3 Tombukt2, Jul 18, 2025 at 6:36 AM
  4. ASRDogman

    ASRDogman Senior Member

    Joined:
    May 29, 2018
    7,255
    3,784
    0
    Location:
    Florida
    Vehicle:
    2010 Prius
    Model:
    Two
    Check the connections to make sure no pins are bent, wires broken, or not being connected properly.
    Are they Toyota sensors? Or parts store ones?
    You don't have to remove the timing cover to check the timing chain.
    Put the engine at tdc and check that the cam sprockets are in the correct position. You won't see the different
    colored links unless you get super lucky, or rotate the engine up to 30 times to get them to align.

    You need a code reader that will clear the codes. Disconnecting the battery for 30-60 minutes might clear them.
    But if you got those codes before replacing them, I doubt either were bad. Though carb cleaner is the worse you
    can use to clean them. It's always best to use the proper cleaner...


     
    #4 ASRDogman, Jul 18, 2025 at 8:56 AM
  5. Louhazosc

    Louhazosc New Member

    Joined:
    May 17, 2025
    3
    0
    0
    Location:
    Maine, USA
    Vehicle:
    2012 Prius
    Model:
    One
    Yeah- actually that's a good point...I was not thinking clearly. I was already at the step of realigning the chain but yes...I should actually check it first!

    Its just very bizarre. Yes, it ran rough for the first 30 min of course, then there was low power during a 60 miles drive now p0016. This "check hybrid system- maintenance required " is over and over. Hybrid battery has a charge, 12v battery at 11.74 by multi meter. The tensioner is really bugging me but if I put a new one in and it was fully released then that's great. It how it's supposed to be. I even had the slack out of the timing chain with the wire trick so I know the marks were spot on. Driving me crazy.
    I'll go hook it up after an overnight battery disconnect and report back.
     
    #5 Louhazosc, Jul 18, 2025 at 10:56 AM
  6. Tombukt2

    Tombukt2 Senior Member

    Joined:
    Nov 29, 2020
    12,240
    2,158
    0
    Location:
    Durham NC
    Vehicle:
    2009 Prius
    Model:
    Base
    N in tensioner you pull like a grenade after correctly verifying all slack on tensioner side to be collected at pin removal and general 12 o'clock positions or whatever it is for given engine. Running rough initially starting should not be a thing if all correct it should fire up and run like a new one more or less . If I have this going on at a startup it's instant off and find out why not leave it running and hope .
     
    #6 Tombukt2, Jul 18, 2025 at 11:38 AM
  7. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    26,521
    17,374
    0
    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    It's every ninth time you see the painted chain links come around, for gen 3.

    It's just the number of links there are in the chain, versus the number of teeth on the sprockets. They'll line up every ninth time you see the painted marks. That's the same as every 70th crank revolution, or every 35th cam revolution. Just math.

    Those won't necessarily be the same numbers for every type of engine. Somebody just has to count the sprocket teeth and chain links and do the math. These are the numbers you get for the Gen 3 Prius engine.
     
    #7 ChapmanF, Jul 18, 2025 at 12:32 PM
(You must log in or sign up to post here.)