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Prius 06 CEL issue

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by waygil, Feb 11, 2009.

  1. waygil

    waygil New Member

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    The CEL has gone on a couple times and was wondering if anyone had an idea what the problem could be. I haven't gone to pull the codes yet. Here's what happened:

    CEL came on last week.
    Checked gas cap, looked ok.
    Went off about 4 days later.
    CEL came back on last night.
    Checked gas cap again. looked ok.

    Here's the part that worries me and I'm not sure if it's related to the above.....

    This morning turned car on and went to Car Wash about a mile away. Cabin started to heat up. I turned the heat off while waiting in the Car Wash. Once finished, I turned the heat back on. Cold air was blowing into the cabin. Drove on highway for 5-10 miles and still no warm air at all. (I should have heat at this point for sure) Pulled over, rebooted the car, and started to get heat again. Turned climate control off and on multiple times during my 1 hour commute and there were no further problems.

    So I guess my questions are:

    Any initial guess what could be wrong? There's no red triangle light, just a CEL. I have not noticed anything else out of the ordinary with the car during the past two weeks. (we drive about 75 miles a day)

    Can I just get a cheaper ODBII code reader rather than the scanguage and pull the CEL codes?

    Thanks for any help!
     
    #1 waygil, Feb 11, 2009
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Regarding the CEL, when you inspect the gas cap, take a look at the rubber O-ring. It should be in good condition and undamaged. When you install the gas cap, tighten it sufficiently so that it clicks at least once.

    Since Prius has multiple ECUs, a generic OBDII code reader, including Scan Gauge, may or may not retrieve all DTC. If you want to buy a code reader I suggest that you purchase one that claims to be compatible with the Toyota CAN, and see what codes appear.
     
    #2 Patrick Wong, Feb 11, 2009
  3. waygil

    waygil New Member

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    I'm supposed to take a trip up to Maine for the long weekend. If I can't get it into the dealer until next week do you think it will be safe to drive? Like I said I'm only getting a CEL light and no Red Triangle.
     
    #3 waygil, Feb 11, 2009
  4. waygil

    waygil New Member

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    UPDATE:

    Went to my local autozone and pulled the CEL code.

    It's the infamous P1121 which would indicate a problem with my Coolant Recovery System.

    Since I had that one issue with the cabin heat could I also have a problem with my Rotary Water Valve?

    Should I be able to wait until next week to get this fixed and go on my trip this weekend?
     
    #4 waygil, Feb 11, 2009
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P1121 "Coolant Flow Control Valve Position Sensor Circuit Stuck"

    You are right; the problem is likely the coolant valve that directs engine coolant to the storage canister or to the cabin heater. This is why your cabin heater didn't work.

    I personally would be hesitant to take the car on a long trip, knowing that the engine cooling system has this problem. I'm not sure whether failure of the valve will cause engine cooling problems or not.
     
    #5 Patrick Wong, Feb 11, 2009
  6. Mike Dimmick

    Mike Dimmick Active Member

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    There are three positions for the valve:

    A - sending coolant to tank from engine or to engine from tank
    B - sending coolant from engine to both tank and heater
    C - sending coolant from engine to heater

    Position A is used at startup (tank to engine) and after engine stop, to recover hot coolant. In normal operation the valve is in position C. Position B is used occasionally to heat up the thermos while the engine is running.

    Since your cabin heat isn't working, I'd guess that it's stuck in position A. It could be stuck partway between the positions, of course.

    Looking at the system diagram, coolant always circulates via the engine if the engine belt-driven water pump is running. There are two other electric pumps, one to pump water through the cabin heater when the engine's off, the other to pump through the thermos to reheat the engine. The thermos pump produces a flow opposite to the normal direction of flow in the system. It's not clear whether the electric pumps restrict motion of the fluid when not operated - I would hope not.

    I don't think the thermos is ever empty - there should never be any air in the system, it should be completely flooded at all times, so it would be normal for coolant going to the tank to mix with/push out what's already in there back down the return path, through the radiator and back into the engine.

    There are some good diagrams in this document.

    It's a complicated system and I'm actually a bit glad I don't have it (no thermos in the EU)!
     
    #6 Mike Dimmick, Feb 13, 2009
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