Car in limp mode but hybrid battery tests fine... any thoughts on causes?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by steved, Jul 12, 2013.

  1. steved

    steved Junior Member

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    Location:
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    Vehicle:
    2006 Prius
    We have a 2006 with 125,000 miles and last week the car entered what the dealer described as "limp mode" twice in the same day but has been fine since. The limp mode lasted for about 5-10 min on both of the trips (trips were longer than that time) around town and resumed normal acceleration and operation later.

    This occurred when driving it around town on a day with temps in the mid 90's and the car had literally no acceleration. The gas pedal was floored but the car would barely accelerate. The battery cooling fan was on, no warning lights were illuminated, and the engine did not rev up to give full power when the gas pedal was floored.

    I searched the PriusChat forums and the only info I found like this was people who had hybrid batteries which needed to be replaced. I had the battery tested and they said all of the cells were balanced for both voltage and resistance and they couldn't find anything wrong with the battery, cooling fan or car. There weren't any error codes stored and the gas mileage is the same as it has always been.

    Any thoughts as to what else I could have investigated or what might have happened? It scared us as my wife was driving with our kids the first time it happened and almost got in an accident due to making a left turn and suddenly having no acceleration.

    Thanks for your input.
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I'd agree that the traction battery likely has a problem. I suppose you'll have to decide whether you can live with the car as-is until the condition gets bad enough to log a DTC, allowing the problem to be clearly identified.
     
  3. 2k1Toaster

    2k1Toaster Brand New Prius Batteries

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    If the traction battery doesn't have a problem as tested I am inclined to believe there is a subsystem problem causing heat. When the battery is hot, it goes into "limp mode".

    When the fan runs in the back, is it really loud? Can you feel the air movement with your hand there? I am thinking possibly your fan is clogged. Do you or have you (or previous owners) had shaggy dogs in the vehicle? They're known to clog up the fan.

    I would purchase a Scangauge, or if you have a Android smartphone get Torque at a bluetooth transceiver for the OBDII port. Then you can monitor the voltage, current in/out of the pack, temperature of the pack and that sort of thing. If you see the temperature OK, but the voltage is swinging wildly between 180v and 250v then the battery is definitely going. if you see a stable battery but the temp is just climbing, it might be something else you can track down.
     
  4. nh7o

    nh7o Off grid since 1980

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    I agree with the above, but would add that in testing the battery cooling fan, the dealer did not actually look at it. They probably just ran Techstream and found that the motor tested OK from the battery ECU port, but that does not necessarily indicate that there was sufficient air moving to keep the battery cool. Also, there have been reports that the air escape for the battery cooling system can become blocked, so that is something to check as well. This is next to the 12V battery vent area.

    Run the AC when it is hot to keep the battery cool as well as the occupants.
     
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