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P1121

Discussion in 'Gen 2 Prius Technical Discussion' started by HOWFAST, May 22, 2014.

  1. HOWFAST

    HOWFAST Junior Member

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    2005 Prius, 105K miles when the check engine light came on.

    Scanner report: P1121 accelerator pedal position sensor range/performance problem.

    Fix: Coolant flow control valve. (Even though it was still working)
    Part number: 16670-21010

    After the install I did not have a scanner to clear the code. After 50 to 100 miles the check engine light cleared itself. Make sure you get all the air out of the coolant system when doing this install. Driving uphill is the best way to find out if there is air in the system. (Red Triangle will come on)

    Just wanted to share.

    Gus//
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    DTC P1121 means that the engine coolant valve had failed, which makes sense since you replaced the valve and the DTC went away. That code has nothing to do with the accelerator pedal position sensor. Codes that relate to that sensor would be P0120-P0123, P0220-P0223 and P2135.

    You can clear DTC logged by most ECUs (besides the skid control and SRS ECUs) by disconnecting the 12V battery negative terminal for a few minutes, then reconnecting.

    Rather than risk overheating the engine by driving uphill, I suggest that you diligently work on getting air out of the system by revving up the engine with the heater temp set to MAX HEAT and the fan set to the top speed while the Prius is parked. Listen for air gurgling in the heater core. Since the engine is not under load, it can withstand being operated without some coolant, better than it can when being driven on a mountain.

    When you no longer hear air gurgling around, make sure the radiator is full, then take the car for a drive. Then park the car and let it cool down.

    After the engine is cold, check the radiator level again and fill as needed. Repeat the heating/cooling/fluid replenishment cycles until the radiator level does not drop from full.

    If the coolant heat recovery canister is drained, then it is necessary to run the CHRS pump when refilling the canister and I have previously posted on how to do that by shorting the switched contacts on the CHRS relay.
     
    JasK likes this.
  3. HOWFAST

    HOWFAST Junior Member

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    Patrick, thanks for the better ideas. You have a lot of useful knowledge about these cars. Fortunately the hill I went up was right next to my house. As soon as it came on I turned right back around and headed home. No real time for the car to get hot.

    Gus//
     
  4. JasK

    JasK New Member

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    Hey Patrick, I was following your thread thoroughly. I have one specific question regarding my prius. I got coolant control valve changed and then I topped up coolant in radiator. My car usually runs all day because it has been used as a cab. Now I am noticing I have to add more coolant in radiator say after 12 hours because level goes down and engine getting hot sign with a PROBLEM message shows up on screen. There wont be any warning sign the day when I top that coolant level in radiator. In town there is no sign but it starts showing up and goes off after 1 day drive. Surprisingly there is no change in coolant level in reservoir. Pressure is also build and no coolant traces on floor or anywhere. I would thankful for your reply.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. How many miles on the odometer?
    2. Look at the engine coolant pump for a pinkish stain (which is dried antifreeze) on the inside of the pump pulley, on the air conditioner compressor housing below the pulley, or perhaps a pinkish spray on the hood sound insulating pad. If you see any of those signs, replace the engine coolant pump now.
    How to replace engine coolant pump and thermostat | PriusChat
    3. Look at the engine oil on the dipstick. Are there any problems like a milky consistency which would indicate coolant leaking into the engine oil due to a blown head gasket?
    4. Are any other warning lights on, such as the check engine light?
    5. Does the cabin heater work? When the heater is turned on do you hear air bubbling in the heater core? If the heater does not work and/or you hear air bubbling, then you need to have the engine coolant system purged of air, which I have posted how to do.
    Changing engine coolant | Page 2 | PriusChat See my posts 22 and 42
    6. Was the coolant heat recovery system canister drained at the time the engine coolant valve was replaced? If yes, the CHRS canister has to be refilled, which I discuss in my post about changing engine coolant referred to in #5 above.
     
    #5 Patrick Wong, May 15, 2015
    Last edited: May 15, 2015
    valde3 likes this.
  6. JasK

    JasK New Member

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    Thanks for the reply.
    1. 120,000 miles on odometer
    3. Engine dipstick show only oil and no coolant or white material or no smell no burning smell. I confirmed it yesterday too.
    4. There is Check engine light which is pretty common in cabs. They usually go 5000 miles in a month.
    5. Cabin Heater had a problem, there was no heat that why we changed coolant control valve, it worked properly for a while and now if coolant level is low no heat asa i put more coolant say upto neck of radiator, heat starts working. I have always heard some gargling sounds around cabin area.
    6. I have to check about canister point. They were given empty canister, I am not sure did they filled it up or not.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    4. Get Mini VCI so that you can read the current DTC logged by your car, to see what other problems might exist. This needs a Windows XP or Windows 7, 32 bit OS laptop to run the software.
    6. The coolant heat recovery canister is located in the driver's side fender, in front of the tire. You have to remove the fender lining for access to the canister. You may want to visually inspect the canister to ensure it is not damaged (from an accident) and that it and its connecting hoses are not leaking coolant.