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P1121+P1116 Write-Up and Troubleshooting

Discussion in 'Gen 2 Prius Technical Discussion' started by tidesofthesky, Sep 6, 2020.

  1. tidesofthesky

    tidesofthesky Member

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    Location:
    Salem, OR
    Vehicle:
    2007 Prius
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    Base
    Hello Everyone.

    I'm working my way through the diagnostics for P1121 Code, and a brand new P1116 code!

    Here are the facts:

    -My car has been making this noise (mp3 file located in this thread). I assume it is the Coolant Control Valve. coolant valve cycling on and off? | PriusChat

    -Car had code P1121, with no other codes stored or pending

    -Replaced the coolant control valve with one from wrecking yard.

    -Currently have a new P1116 code active, with a P1121 pending.

    Both diagnostic trees are very short. I'll start with the P1121.

    1. First step is to measure from pins E2 to WBAD on the ECM while activating the valves in techstream.
    - There are 3 ECMs behind the glove box. The middle one is the main ECM that we will be testing.
    IMG_20200906_184604.jpg
    - See screenshot of the service manual for the 2 pins that we will be probing for voltage. Left side of the image is the top of the ECM in the vehicle. E2 is brown, WBAD is pink.
    IMG_20200906_185818.jpg
    - I used sewing pins to back probe the connectors. Just stick the pins into the back of the connector next to the wire, then hook alligator clips to them for testing.
    - In Techstream, go to the Engine/ECT module, then click on Active Test. This will bring up a list of tests. Choose one of the valve tests- 3, 4 or 5. A small box will appear, you press the forward button in the box to switch the valve from off to on.
    - For valve 3, the voltage on your multi-meter should read about 2.5 volts. For valve 4, 3.5 volts, and for valve 5, 4.5 volts.
    IMG_20200906_184528.jpg
    If those fail, you replace the Coolant Control Valve.

    Mine passed those tests just fine.

    The only other step for diagnosing P1121 is to check for cooling system clogging. If no clogging is found, then replace the ECM.

    I'm not sure where to begin checking for clogging. So I moved onto diagnosing P1116.


    The diagnostic tree for P1116 has basically 2 steps.
    1. Check for cooling system clogging.
    2. If no clogging is found, replace the CHS temperature sensor.
    I have some questions before moving forward.
    1. Where would I begin checking for cooling system clogging? Would draining/flushing the system be the next step in that process?
    2. Should I go ahead and replace the CHS sensor? Could that be the cause of both codes? Seems like it would be the easiest, and it'd be cheap at pick a part.
    3. Is there any chance that one or both codes are related to low coolant? I did follow the refill procedure after replacing the coolant control valve, ie opening the bleed valve on radiator, filling, activating the water pump, adding coolant, repeat etc. But perhaps there is still air somewhere in the system? And maybe there was some air in there before as well?


    Would love any insight you have. Thanks!
     
  2. dolj

    dolj Senior Member

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    I haven't had the pleasure of doing this myself and nor can I remember any other posts of where anyone documented clearing clogging from the engine cooling loop. I do recollect someone clearing clogging from the inverter cooling loop and he had what looked like a black foam substance that came out. Further, I have seen a picture of this same substance inside the inverter cooling fins causing an impaired cooling for that inverter.
    if the system is drained, I would remove the radiator hoses, as well as the radiator itself, and check blockages to start with. I would use a water hose with good pressure to flush the engine block and the heater block (both of them both forwards and backwards) to ensure those part were free of clogging. The rest you will have to ad-lib as required.
    You could, but I don't think so. But if you do, use a genuine OEM (Denso?) part. Aftermarket sensors for this part (also the coolant control valve and the inverter coolant pump) do not have a good track record.
    Again, I don't think so. Perhaps there is still air in the system, but it sounds like you did the bleeding correctly and, I presume, you checked the radiator level (not the overflow tank) every day for a week or so and topped up as required? The trickiest part of bleeding the air out the North American model is the CHRS tank. Lookup a post by Patrick Wong who documents the process quite well, including how to run the CHRS pump to clear the air out of the tank. I think he was just changing out the SLLC in the engine coolant loop in a timed service interval. Use the "Advanced Search" options (by clicking on the "More..." button in the window that pops up when you click in the search box at the top right of the page.

    Further, if you are not going to use Toyota SLLC, drain out the entire loop and flush before refilling with the coolant of your choice. Most people just stick with Toyota SLLC to avoid all the hassle.
     
    #2 dolj, Sep 6, 2020
    Last edited: Sep 7, 2020
  3. tidesofthesky

    tidesofthesky Member

    Joined:
    May 18, 2020
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    Location:
    Salem, OR
    Vehicle:
    2007 Prius
    Model:
    Base
    So much great info! Thank you for taking the time to write all that up. I'm going to take some time to think all that through and then figure out my next steps.

    Sounds like flushing the system may be the solution.

    Thanks for the tip on the CHS pump- I think the manual actually includes that in the bleeding procedure. I used techstream to activate it for 30 seconds. So hopefully the cooling system is good to go. I finished this up yesterday and topped off fluid this morning. I'll continue doing so til it levels off.

    And thank you for the direction on the coolant. I just did a deep dive on the SLLC vs aftermarket pink and didn't realize there was so much to know.

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