2017 prius rough idle and TONS of codes, help!

Discussion in 'Gen 4 Prius Care, Maintenance and Troubleshooting' started by nickelbn78, Feb 24, 2025 at 9:31 PM.

  1. nickelbn78

    nickelbn78 New Member

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    2017 prius two, 240k miles. getting numerous codes that just keep coming back. it runs fine when cold. then once warmed up it will not idle properly and keeps throwing all these codes. I've completely replaced the head gasket. new thermostat. new maf sensor. new ect sensor. rerouted coolant lines because heat exchanger was leaking. hybrid battery appears to be fine. spark plugs are working. I've cleaned the throttle body. it runs if I keep on the gas but shakes like crazy if I let off. I don't understand how all these codes keep getting thrown. I actually just went ahead and took it out and drove it up and down the road and it seemed to have no problem once I got it above idle speed I can drive all the way up and down the highway with no check engine light or anything and it did just fine. It's only when it slows down to around idle speed that it starts jerking and running rough. After I drove it about 10 miles I brought it back to the garage and as I was pulling into the garage it started jerking again and then threw up the yellow triangle and the screen says "check engine" and the check engine light came back on as well of course. please help.
     

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  2. Brian1954

    Brian1954 Senior Member

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    All the trouble codes that are shown in your screenshot are for archived (inactive) codes. If you have the check engine light, you should have current (active) codes to be read. Get the current trouble codes, and people should be able to help you.

    Based on the inactive codes, the engine severely overheated. Was the head taken to a machine shop to get reworked when you replaced the headgasket?

    Note: The screenshot for the Dr Prius app is only showing 9 battery blocks. It should show 14 battery blocks, so there is a problem with the data that the app is seeing. This could be caused by an old version of the app or a problem with the OBD2 Bluetooth dongle that you are using.
     
    #2 Brian1954, Feb 26, 2025 at 2:36 PM
    Last edited: Feb 26, 2025 at 2:42 PM
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  3. nickelbn78

    nickelbn78 New Member

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    Those are current. I am going in and clearing all of the codes and then the next time I try to run the car all of those codes come back again
     
  4. nickelbn78

    nickelbn78 New Member

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    Oh by the way, no I did not take it to a machine shop, however I know the engine has not overheated since I fixed the head gasket. I have been watching the engine temperature anytime I have started the car. The car has never even ran for very long because of this shaking issue at idle. I did take it for one long drive for about 5 MI to see what would happen but I watched the temperature of the entire time and it stayed at 190 the whole time. Well there was one time I was testing it before I found out that the heat exchanger was leaking coolant and the engine temperature did get up to around 210 and I shut it down at that point.
     
  5. nickelbn78

    nickelbn78 New Member

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    So I just went and bought a new 12 volt AGM battery because the one that was in there from the previous owner was a standard battery not an agm. I did a 5 volt reference test to my sensors such as the ECT sensor and I was only getting 2.5 volts when I should be getting 5V. After replacing the battery now all the sensors are showing 5 volts like they should. I was feeling optimistic this was going to solve my problem but after clearing all the codes and starting up the car again it still was shaking like crazy until I push on the gas pedal to rev up the engine and then it Smooths out but as soon as it gets back down to idle speed it just wants to shake. I went ahead and took it for a drive anyway and every time the engine would get to the point where it would want to shut itself down it would start shaking and just like it did to me two days ago once I got back from my drive and went to pull up to my garage suddenly the screen popped up "check engine please pull over to safety within the next 3 Mi and shut down your engine" and the check engine light came on. I pulled into the garage and ran the codes once again and this is what I am getting. There is only one active code for engine failing to start. It is running however it just refuses to run smooth in idle
     

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  6. MAX2

    MAX2 Active Member

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    Starting problems are usually related to fuel and air problems, which is why the fuel-air mixture is not formed correctly.

    Other possible causes are the fuel pump, spark plugs, ignition coils, air intake duct, air filter, throttle valve.

    Have you checked the condition of the throttle valve?

    If it is dirty and jammed, then the mixture is not formed correctly and the engine rattles and stalls.
     
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  7. BiomedO1

    BiomedO1 Senior Member

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    If it runs fine but just doesn't want to idle - it's likely a mixture issue. Too lean. You stated that it starts fine and runs when cold. That means one or more sensors is reporting bad data to the ECU forcing an extra lean mixture, killing the engine at low warm idle.
    If you still have the old MAF, I'd put it back in, ditto with the ECT. If you were given the wrong spec. part that's going to cause bad mixture data calculations. I would also suspect the upstream O2 sensor too. All this could be checked with a better scan tool - one that can read the raw data from each sensor.

    Hope this helps...
     
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  8. nickelbn78

    nickelbn78 New Member

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    yep. I cleaned the throttle body first. didn't work. so then i replaced the whole throttle body, still no. i did unhook the 12v battery to reset everything. got a new agm 12v battery. still no. it has a new air filter. I've changed the spark plugs. I've checked both ect sensors and wires. maf sensor i switched back to the original. fuel pressure checked and running well at 50. no pressure loss at 15 minutes so no leak from fuel injectors. the ignition coils have to be working because it runs and drives at faster then idle speeds. so frustrated right now...
     
  9. MAX2

    MAX2 Active Member

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  10. xliderider

    xliderider Senior Member

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    Are you sure you didn't miss plugging a connector in or putting a vacuum hose back on? Or, could you have a vacuum leak at the throttle body gasket?

    SM-G781V ?
     
    #10 xliderider, Feb 28, 2025 at 2:28 AM
    Last edited: Feb 28, 2025 at 2:49 AM
  11. nickelbn78

    nickelbn78 New Member

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  12. MAX2

    MAX2 Active Member

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    After replacing the throttle valve, was the following procedure performed or not?

    1. PERFORM INITIALIZATION

      Note
      • Be sure to perform this procedure after removing and reinstalling the throttle body assembly or any throttle body assembly components.
      • Perform the following procedure after replacing the throttle body assembly or any throttle body assembly components. The following procedure should also be performed if the throttle body assembly is cleaned.
      1. Connect the GTS to the DLC3.
      2. Clear the DTCs.
      3. Perform "Inspection After Repair".
      4. Put the engine in inspection mode (maintenance mode).
      1. Start the engine without operating the accelerator pedal and check that the MIL is not illuminated. After the engine is warmed up, check that the idle speed is within the specified range with the A/C switch off.

        Standard
        950 to 1050 rpm
        Note
        • If the accelerator pedal is operated, perform the above steps again.
        • Be sure to perform this step with all accessories off.
        • Make sure that the shift lever is in P.
      2. Perform a road test and confirm that there are no abnormalities.
     
  13. nickelbn78

    nickelbn78 New Member

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    I reset everything by unplugging the 12v battery and I cleared all codes, but i did not put it in maintenance mode.
     
  14. MAX2

    MAX2 Active Member

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    Note
    • Be sure to perform this procedure after removing and reinstalling the throttle body assembly or any throttle body assembly components.
    • Perform the following procedure after replacing the throttle body assembly or any throttle body assembly components. The following procedure should also be performed if the throttle body assembly is cleaned.
     
  15. nickelbn78

    nickelbn78 New Member

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    I understand, but I have also worked on several Priuses and I have taken off the throttle body and cleaned them numerous times and never did this procedure and they all started right back up and ran just fine. So I have a hard time believing that's my problem but I'll give it a shot and see.