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What are the most common check engine light (CEL) or DTC codes

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by White Gold Prius, Apr 19, 2011.

  1. White Gold Prius

    White Gold Prius Junior Member

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    Hi guys. I've had a 2005 Prius for almost 2 year and 50,000 miles now and had no problems. recently I decided to do an inverter recall and them some "necessary" maintenance (TB, transaxle fluid, etc). How I have an intermittent CEL, P1112 (Intake air temp sensor) coming on every other day. Before I thougt Autozone had another DTC detected (1121? it had something to do with a cooolant stacked too high?)

    What are the most common check engine light (CEL) or DTC codes and how to deal with them? Thanks.
     
    #1 White Gold Prius, Apr 19, 2011
  2. seilerts

    seilerts Battery Curmudgeon

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    P0112 is the intake air temp sensor malfunction, short circuit. You could try cleaning it (part of the MAF sensor) and look for rodent chewage in the wiring. There's a pretty short list of things to replace, being either the MAF or the engine computer (ECM)

    P1121 is a somewhat more common occurrence, the coolant flow control valve. First thing to check is your coolant level and engine water pump. This code can show up when coolant is running low due to a failing water pump, or an airlock in the system due to an improper bleed during a coolant fillup. If it is the valve itself, that is a few hundred dollar dealer repair, but you get a complete engine coolant exchange in the process. Same deal for the engine water pump repair in terms of cost and getting a coolant exchange.

    P0456 indicates an EVAP problem, almost always due to user error in putting the gas cap back in place after a fill-up.

    P0A93 (inverter coolant overheating/IC pump malfunction) is the most common, but that will be far less frequent in light of the recall.

    P0300 with P030x, x={1,2,3,4} indicates a misfire in cylinder x. Could be water in the spark plug well(s), bad spark plug, bad injector, bad wires, etc...
     
    #2 seilerts, Apr 20, 2011
  3. White Gold Prius

    White Gold Prius Junior Member

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    Thanks for your help. I did replace the engine coolant, inverter (water pump?), spark plugs, PCV valve and did TB cleaning in one shot. Could any of these affect my intake air temp sensor, why is it intermitent and what are the consequences of not doing anything with it? Thanks again.
     
    #3 White Gold Prius, Apr 20, 2011
  4. seilerts

    seilerts Battery Curmudgeon

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    Okay, changing out the engine coolant most likely explains the P1121. Do you still get that one, or was it a one-time reading at Autozone?

    The consequence of P0112 could be that the engine stays in open-loop and fuel economy will be poor.
     
    #4 seilerts, Apr 20, 2011
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes. If you got throttle body cleaner on the MAF sensor which includes the air temp sensor, that is not helpful.

    It would be best to remove the MAF sensor from the air cleaner housing and use MAF cleaner to clean it. Good luck.
     
    #5 Patrick Wong, Apr 20, 2011
  6. White Gold Prius

    White Gold Prius Junior Member

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    This was 1-time reading from Autozone but then the P1112really made me worried.

    After I did the package maintenance, I had 2 weeks of smooth driving before the CEl came on. Now it goes steady after 5 min driving in the morning and stays on.

    Patrick, if TB cleaning could be the cause, why the CEL wouldnt show up for 2 weeks after. Could it be something else. Should I take it to my locals Toyota (free diagnostics but outrageous prices) or to the certified shop that did the maintenance for a check-up (decent prices but still uncertain about the quality of their work)? :(
     
    #6 White Gold Prius, Apr 20, 2011
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The throttle body cleaner leaves an oily residue. It might take a while for the residue to pick up dust in the air and cause a problem with the MAF sensor.

    The problem also might be a loose wiring harness connection to the MAF sensor.

    Yes, the root cause might be something else. However, since it appears that you have the ability to clean the MAF sensor, I suggested you do that prior to seeking help to determine the problem.
     
    #7 Patrick Wong, Apr 20, 2011
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