My IPM was replaced, now my gas mileage has dropped from 42-45 all the way down to 28-35.

Discussion in 'Gen 3 Prius Fuel Economy' started by Akira Takamedo, Nov 20, 2017.

  1. Akira Takamedo

    Akira Takamedo New Member

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    And the best part is, the dealer I took it to won’t look at it, said there’s nothing they can do. He blamed the cold weather and having to reset the battery when the IPM was relaxed which somehow messes with all the data.

    This is ridiculous, the whole reason I bought this car was to get over 40 MPG. I don’t know what else to try except check the tire pressure or try a different dealership, maybe call the Toyota 800 number. I don’t care how cold it is, my car now has 32 MPG on average and that’s not acceptable.
     
    #1 Akira Takamedo, Nov 20, 2017
    Mendel Leisk likes this.
  2. bisco

    bisco cookie crumbler

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    this has been reported before. how are you measuring mpg's?
     
    #2 bisco, Nov 20, 2017
  3. fuzzy1

    fuzzy1 Senior Member

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    The winter excuse is valid, though not for that big a drop. Battery reset of stored data is bogus, the car should do quite well right out of the gate after a reset.

    But lacking a Check Engine Light, any common shop cannot reasonably deal with nebulous MPG complaints. There are many possibilities, much having to do with driver style and particular usage, and the labor cost of helping find the problems and improve driver behavior is enormous and unprofitable.

    This questionnaire can help us provide you some guidance:
    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat
     
    #3 fuzzy1, Nov 20, 2017
  4. Mendel Leisk

    Mendel Leisk Senior Member

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    There was a recall involving an inspection of the inverter and software update, the latter being to shelter the inverter from sudden acceleration stresses. Anyway, a few owners reported marked drop in mpg after this update.

    Just wondering if there could have been something like this applied at the same time as the IPM replacement? And you drew the short straw, getting the mpg drop from that.
     
    #4 Mendel Leisk, Nov 20, 2017
  5. cproaudio

    cproaudio Speedlock Overrider

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    Get a Scangauge and program the X-Gauge to monitor battery amerage, mechanical braking, battery SOC and battery voltage. These readings will tell you how efficient your regen and electric assistance are. After reprogramming the IPM, I've noticed regen had been relaxed to compensate the weather. During hot months, regen cuts out completely and only rely on mechanical braking even though the HSI shows maximum regen. When my car loses regen, my MPG dropped to low 40s where normally could get mid 50's. During summer months, Driving without AC has about the same MPG as driving with AC. This is due to very little to no regen. This kind of force me to drive with AC during summer. I know you're complaining about winter mileage, Scangauge will show you how much electric assistance your engine is getting. It doesn't solve your poor MPG after IPM replacement but at least it shows you how your hybrid system is working.
     
    #5 cproaudio, Nov 21, 2017
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