2006 Prius codes P0420, 0171, 1121, and more rebuilt battery

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Wville, Apr 22, 2019.

  1. cnc97

    cnc97 Senior Member

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    Carb and choke spray, brake cleaner, mass air flow cleaner. Any flammable automotive type cleaner.
     
  2. Wville

    Wville New Member

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    Lol! Got it!
    Alright, I’ll do that in just a few minutes then! Thanks!
    What would be the next suggestion if there aren’t any leaks ?
     
  3. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Replace the MAF sensor with the correct Toyota part or find the Denso equivalent.
     
  4. Wville

    Wville New Member

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    Got home earlier, put the car in inspection mode, and sprayed every hose and tubing and air intake area possible, no issues.

    The MAF is a Toyota part but is not new, I did order the replacement Just now since it was fairly inexpensive.
    What other suggestions might I try in the mean time.
     
  5. cnc97

    cnc97 Senior Member

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    The air box is complete and intact, with the prefilter/charcoal filter still attached to the lid? No cracks or other defects? The replaceable element itself is not torn and the rubber seal
    Intact? Assembled correctly?

    I know these sound like silly questions, but some of these little things might be responsible for it.
     
  6. cnc97

    cnc97 Senior Member

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    This list is from the 2010 diagnostic manual, but it has something listed that I would not have thought of to check. The coolant temp sensor. Rationale being if the ECM THINKS it’s -20 F, the A/F ratio would need to be richer then if it’s 80 F. Therefore the ECM would turn on the C E L.
     

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  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I do not think the coolant temperature sensor is a problem because you had previously posted an image showing that the engine ECU thinks the coolant temp is 185 degrees F, which is normal operating temperature. The sensor is located on the engine head and you may have to remove the inverter reservoir for access.

    Regarding P1121, I understand that you replaced the engine coolant valve. When you refilled the engine coolant, did you run the CHRS pump manually to refill the coolant heat recovery system canister located in the front driver's fender in front of the tire?

    Assuming the valve is working properly, that code can still be logged when air remains in the engine coolant loop. Check the coolant level in the radiator, do not depend just on looking at the coolant level in the reservoir. Also make sure the cabin heater produces good heat. If you hear air bubbling in the heater core, that also is indicative that air remains in the engine coolant loop.

    Regarding P0171, I understand you tried to spray the hoses, etc. to see if you could induce an engine idle speed change. Did you also spray the junction between the throttle body and the intake manifold? That could be a source of a vacuum leak if the gasket is bad or the throttle body is loose. Also inspect the oil filler cap rubber gasket, and the gasket on the engine oil dipstick. Those are also possible sources of a vacuum leak. I understand you are going to replace the MAF sensor - make sure the rubber O-ring on that sensor is good.

    Regarding P0A80, you had previously posted images showing very strange voltage readings from some module pairs. However I think those are bogus readings from your diagnostic code reader since there are only 14 module pairs.

    The battery ECU measures voltages of 14 module pairs (there are 28 modules total). Each module pair should measure around 15.8V and the voltages should all be within 0.2V of each other. If you see voltages much lower than that, that is indicative that at least one of the modules in the pair is failing. If you see voltages much higher than that, that implies that the sense wires connected to the battery have a problem.

    Your code reader is also showing strange temperature readings from the transaxle. I don't know if those readings are valid which implies that a sensor is disconnected, or if they are bogus.

    It would be better if you were using Toyota Techstream which you potentially can run on a Mac if you install Boot Camp and Windows 7, 32 bit OS.
     
    #27 Patrick Wong, Jun 23, 2019
    Last edited: Jun 23, 2019
  8. Wville

    Wville New Member

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    Thanks for all of the tips! There is no vacuum leak, I sprayed nearly... everything... lol

    I will purchase an inexpensive windows pc to run Toyota tech stream on before I mess with the os on a $3000 MacBook Pro.

    This last tank is back to getting poor Mpgs.

    I’m anxiously awaiting the MAF to arrive; and I may just go ahead and locate the durn temp sensor and replace it too... I already have the sensor, just seemed like too much since I never could physically see it.

    Honestly, the transaxle fluid might need to be replaced or changed, but I can’t help but wonder if any of these small issues could actually lead to 25-27 mpg. And that code continuing to return....

    Thanks!
     
  9. Skibob

    Skibob Senior Member

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    What brand o2 sensors did you replace your old ones with? Some people here have experienced problems with using aftermarket o2 sensors, especially the front air/fuel mixture one. Toyota Factory or Denso (Toyota Factory) are the only ones you should use.
     
  10. Wville

    Wville New Member

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  11. Skibob

    Skibob Senior Member

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  12. Wville

    Wville New Member

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    Yeah,
    Found out today I had the wrong o2 PID programmed in the OBD app. Got it corrected both are showing values now. Pics to follow
     
  13. Wville

    Wville New Member

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    Do any of these values look weird or bad to you guys ?
     

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  14. Wville

    Wville New Member

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    That’s really the only part I’ve went cheap-o on, because they all pretty much do the same thing, and the upstream seems to range between $140-$250 for this car ... so I bought these and I’m not opposed to replacing only after I’m 110% certain the cheap ones are the cause of the issue. But considering the same issue is occurring since prior to the o2 sensors, except now the o2 codes are good.... idk lol
     
  15. Wville

    Wville New Member

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    So, to update:

    Spent 4 1/2 hours Sunday replacing the engine coolant temperature sensor only because the how-to videos online and DIY tutorials are very slim to none for resourceful info.
    Installed the new sensor put it back together and immediately got the same P0171 code as before + p0117 low circuit.
    After spending 4 1/2 hours in Louisiana heat and being sunburnt to a crisp, Monday I took it to the mechanic who I’ve been paying $200 to replace the sensor sensor sensor itself that I had put in was a faulty sensor .
    Picked the car up today, and replaced the MAF, and the P0171 code has returned.

    During my temperature sensor adventure I discovered that there is massive build up around deal injectors which I was told is not necessarily a bad thing, however it’s possible to feel injectors are all set for the issues that I have experienced. So the Excelerator position sensor and panel will arrive today and I will replace that also.
    After this, it is not remain illuminated my next options seem to be limited to:
    Replacing the fuel injectors

    Replace EFI M Relay ;which I still haven’t figured out exactly which relay this is... since none of my fuses are labeled this and the manual was useless)

    Replace the PCV (positive crank case)

    And then give up

    Any additional recommendations ?
     

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  16. Wville

    Wville New Member

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    Thanks for all of the help so far Patrick, you’ve been soooo resourceful!

    So, there are later updates, but just in the last week or so, the engine coolant temp sensor was replaced, and the MAF.
    My next step is the fuel injectors.
    Since the temp sensor was replaced the P0171 (bank 1 too lean) is still re-occurring with every time I restart the car or after about 30 mins of driving after the code was cleared.
    Now, that code intermittently re appears, and it is sometimes accompanied by P0420 (catalyst system) I’ve seen a Muffler shop and they informed me the CAT was not faulty. So, if injectors don’t resolve the P0171... I’ll be only all the more confused... lol
    Thanks again
     
  17. Patrick Wong

    Patrick Wong DIY Enthusiast

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    This is a reasonable next step.

    In addition I suggest that you raise up the car and make sure that there is no drag from the parking brake on the rear wheels. Also spin the front wheels and check for excessive drag (which goes beyond the wheels rotating each other via the differential within the transaxle case).
     
    #37 Patrick Wong, Jul 13, 2019
    Last edited: Jul 13, 2019
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