Help!!! 2004 got codes: P0505, P0790, P0993. Scary!

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by AllenZ, Sep 25, 2016.

  1. AllenZ

    AllenZ Active Member

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    My 2004 (with all options) first showed brake sign a month ago. I guess it is the rear brakes but not sure.

    I kept driving for 2 weeks, and it suddenly produce a continues high pitch sound whenever it is turned on (can't hear it from outside when doors and windows are closed). And the power brake can't function, it feels like hand brake --- still brakes, but you must use lots of force to push the pedal. On dashboard, the brake sign and ABS lights are on.

    So I bought a code reader, and found the following 3 codes: P0505, P0790, P0993

    Can anyone by reading the codes and description to determine the cause, and the parts needs to be replaced (other than brakes)?

    The car has 245K on it. Generally no problem for the 6 years I owned it.

    Thanks a lot!

    Allen
     
  2. dolj

    dolj Senior Member

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    The continuous high pitch squeal is actually a desperate cry from your car that you need to stop driving it and get help as it has a serious problem.

    Your code reader is probably only capable of reading general engine codes and is not reading any of the specific system ECUs in the car. There should be codes set by the ABS ECU that you're not reading. The codes you detailed are not really meaningful.

    First priority is to get all the codes read, and then it will be more clear where to go from there.
     
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  3. bisco

    bisco cookie crumbler

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    12 years and a quarter million miles, you may want to consider looking for another car.
     
  4. goldfinger

    goldfinger Active Member

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    P0505 - IAC (Idle Air Control) System Malfunction
    P0790 - Transmission mode selection switch -circuit malfunction
    P0993 - Transmissionn fluid pressure (TFP) sensor / switch F circuit range/performance

    If you hadn't said your car was making a sound I would say check the 12v battery. In this case two of the codes point to the transmission. These are generic codes. A factory scan tool will probably give you more information. You could take it to the dealer for a diagnosis. While there you could even stroll over to the show room.
     
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  5. AllenZ

    AllenZ Active Member

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    All great comments!

    Actually I already bought a 2010 Five with Solar Panel! :). I wished that it had adaptive cruise control, but not.
    But I have to at least fix the 2004 before I can sell it for $2000? maybe...
     
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    1. You need Mini VCI to read the codes.
    2. It appears your car has several issues: brake system, throttle body, perhaps a transaxle issue.
    3. The repair cost is likely to exceed $2K so tow the car to your local salvage yard and walk away.
     
  7. AllenZ

    AllenZ Active Member

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    My mechanics said that it is the brake vacuum pump that's needed. I checked on eBay, nothing like that exist. Where can I buy the part? or which term should I use to search? I searched "2004 Prius brake vacuum pump", no result.

    If the repair exceeds $500, maybe I should junk it?

    Thanks as always!

    Allen
     
  8. AllenZ

    AllenZ Active Member

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    My mechanics actually drove the car to his garage, 20 miles away, with almost hand brake only! :) Guess he does that all the time, with lots of confidence!
     
  9. orenji

    orenji Senior Member

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    That's scary! :eek:
     
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The car probably needs a new brake actuator pump. The Prius does not rely upon engine vacuum in the braking system. I suggest you need a better-trained mechanic to service your car.
     
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