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2002 Prius no dash reading for ambient air temp sensor, A/C problems

Discussion in 'Generation 1 Prius Discussion' started by jaygoz, May 12, 2017.

  1. jaygoz

    jaygoz New Member

    Joined:
    May 12, 2017
    2
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    Location:
    Glendale, CA
    Vehicle:
    2002 Prius
    Model:
    I
    Let me start this off by saying that I'm an idiot and probably shouldn't be working on cars. I bought a used Gen I Prius about 6 months ago and while the interior was a little rough and dirty, it has run like a champ. It was a great purchase and has saved me a ton of money and (until now) worry about something going wrong on an expensive car. The dash panel was cracked, so thanks to a thread I found here, I decided to order a new one and replace it myself. It was so brittle, I was able to basically rip it out in chunks and deal with the hardware after. I should've spent more time reading about how to actually deconstruct it properly, but like I said I'm kind of an idiot.

    Anyway, for whatever reason (read: my fault probably, almost certainly), the ribbon cable running from the HVAC controls to the circuit board behind it wasn't connected properly when I put everything back together, and something shorted, capacitors popped, things went wrong. It was like a Michael Bay version of Tron. The radio controls and HVAC controls stopped working, and I lost the ambient temp reading on the main display. It doesn't even say "- -" as some people have mentioned in other threads. It just says "Outside Temp" with no number or anything. I found a used main circuit board (the one with all the radio controls and HVAC controls) on ebay for fairly cheap and replaced it, ensuring to properly attach the ribbon cable this time.

    When I fired it back up, everything worked! It was a miracle. Except for the A/C and the ambient temp reading on the display. The green LED on the A/C button lights up with no blinking, but I never hear the compressor kick in and it doesn't blow cold air. The first thing I did was replace the relay because that was cheap and easy, but that didn't solve anything. I did some digging, and the A/C fault code I get through the "press 3 times and turn to auto" method is 14. But I can't find out what 14 means. And through some more digging, I found out that the ambient temp reading plays an important role in the A/C function. So now I'm thinking, since the A/C light isn't blinking, that all my problems are tied to that little temp sensor. But I have no idea which part to look at or replace to fix it. I'm assuming the sensor itself is fine, but the controller, wherever that lies, isn't. Any ideas or suggestions would be really appreciated.
     
  2. ChapmanF

    ChapmanF Senior Member

    Joined:
    Mar 30, 2008
    23,073
    14,982
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    Location:
    Indiana, USA
    Vehicle:
    2010 Prius
    Model:
    IV
    You can, you just have to know the repair manuals are at techinfo.toyota.com. You should be congratulated for getting this far without them, but if you begin to tire of the excitement, you know where they are. :)

    -Chap
     
    mroberds likes this.
  3. jaygoz

    jaygoz New Member

    Joined:
    May 12, 2017
    2
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    0
    Location:
    Glendale, CA
    Vehicle:
    2002 Prius
    Model:
    I
    Thanks! The honeymoon period has definitely worn off by now. I paid the $15 entry fee and it's already helping. Apparently 14 is the engine coolant temp sensor. Both sensors have the ecu/harness in common, so I at least have a plan of attack.
     
  4. Stallion K

    Stallion K New Member

    Joined:
    Feb 14, 2020
    6
    1
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    Location:
    Honolulu
    Vehicle:
    2002 Prius
    Model:
    N/A
    Hey any update on this? I was given an 02 classic to work on. The AC button doesn't light up, in fact the fan doesn't blow at all AND the outside temp reading on the mfd doesn't say anything but "outside temperature". I replaced the blower motor and resistor. This did nothing. Any ideas on how to diagnose this. I checked the heater fuses under the hood, and they are all intact.

     
  5. 3prongpaul

    3prongpaul Hybrid Shop Owner, worked on 100's of Prius's

    Joined:
    Jul 18, 2010
    954
    716
    1
    Location:
    Boulder Hybids, Boulder, CO
    Vehicle:
    2006 Prius
    Model:
    N/A
    Sounds like an electrical problem. There are plenty of fuses and relays in the Prius and multiple fusebox and relay box locations.. Get wiring diagram and check everything related to HVAC. Then check the AC control panel, but try and access it after removing the glovebox. If you try to remove the entire dash center assembly which contains the AC amplifier/control panel it will likely disintegrate.
     

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  6. Stallion K

    Stallion K New Member

    Joined:
    Feb 14, 2020
    6
    1
    0
    Location:
    Honolulu
    Vehicle:
    2002 Prius
    Model:
    N/A
    Thank you so much, Paul. I will try to look into this. Yeah, I'm definitely not taking out the center assembly. The funny thing is the previous (original if you can believe it) owner had the mfd replaced at the dealer in 2018, and the dealer broke the assembly in the comments section of the receipt so they had to install a whole new one. Lol, the dealer can't even remove it without breaking it. It's just so weird that the AC light didn't light up at all. First things first in Saturday is in going to go in from the glove and see if all the 3 HVAC clips are even plugged in.
     
  7. 3prongpaul

    3prongpaul Hybrid Shop Owner, worked on 100's of Prius's

    Joined:
    Jul 18, 2010
    954
    716
    1
    Location:
    Boulder Hybids, Boulder, CO
    Vehicle:
    2006 Prius
    Model:
    N/A
    If the center dash panel was new in 2018 it won't be brittle and could be removed, but you should not have to remove it unless you need to replace parts. The wiring harness can be accessed after removing the glovebox and pocket/CD player below the radio.
     
    mroberds likes this.
  8. Lisa Boughamer

    Lisa Boughamer New Member

    Joined:
    Mar 24, 2023
    12
    1
    0
    Location:
    New Mexico
    Vehicle:
    2002 Prius
    Model:
    N/A
    Anyone ever find a fix? I have the same problem, checked all relays, fuses, wires, changed out the amplifier board, nothin works. Thank you