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Help with check engine light and alternatives to overpriced dealership repairs.

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by Awsick, Jul 3, 2012.

  1. Awsick

    Awsick New Member

    Joined:
    Jul 3, 2012
    5
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    Vehicle:
    2005 Prius
    Model:
    II
    My '05 Prius check engine light has been on for a while now, at first it would turn on for a while then turn off but now it is staying on. I took it to AutoZone and they ran a diagnostic and it returned the codes P1121, P1123, P1150, P1116. I've searched a few sites and many think it is an issue with the water pump which has a recall, but I already got my recall about 16 months ago.

    Some other background info... I deliver Pizza, it has been 97+ for the past week and during the day I notice a significant drop in MPGs and then as soon as night rolls around, my MPGs shoot back up. I have about 155,000 miles and haven't done any mods to the car. Purchased new. I prefer to drive with my windows down instead of with A/C and when I turn my car off I hear a vent in the back of the car shut off. My coolant levels are fine.

    So my real questions are, what are some possible issues I might have with my Prius? What options do I have towards diagnosing the problem myself? is it possible? Would my best bet be to just stick to the dealership? Do any of the possible issues have easy/cheap/DIY fixes?
     
    #1 Awsick, Jul 3, 2012
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    18,200
    6,482
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    Location:
    Green Valley, AZ
    Vehicle:
    2015 Prius
    Model:
    Two
    It is likely that the root cause is a failed engine coolant flow control valve. The fix is to replace that valve. If you do a search you will find several posts about that valve and what is involved in replacing it so you can decide whether your DIY skills are up to that. You can also obtain repair manual info at techinfo.toyota.com which is a subscription website.

    Regarding your reduced mpg during the day, I suggest you try using your AC system set to a comfortable temperature to see what happens to your mpg. Your traction battery would benefit from the cooler conditioned air and you might also enjoy cooler, dehumidified air.

    Regarding the sound that you hear when you turn off your car, I think it is more likely that you are hearing the system main relays within the traction battery enclosure opening. There is no vent in the rear of the car that would open and close upon a change from READY to IG-OFF.
     
    #2 Patrick Wong, Jul 3, 2012
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