Intermittent Red Triangle - not diagnosable ...

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by frustratedInSeattle, Nov 8, 2025 at 9:43 PM.

Tags:
Page 3 of 3
  1. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,758
    8,562
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    How does the car drive now? Do you notice any hesitation? P0301 and P0304 are misfire codes.

    Disappearing coolant is never a good sign, if your car has overheated it could have a potential head gasket issue, which can lead to misfires when coolant is present. If the car is driving relatively normal now with good power, I would just not do anything for the next week. Make sure the levels of your coolant doesn't continue to drop for no apparent reason. If after a week of driving and everything seems normal, you can delete all the codes again and see which ones come back.

    Misfire on the 2nd generation Prius doesn't necessary have to do with plugs and coils, many times it's related to bad fuel injectors.
     
    #41 JC91006, Nov 11, 2025 at 9:34 PM
  2. frustratedInSeattle

    frustratedInSeattle New Member

    Joined:
    Saturday
    22
    1
    0
    Location:
    Washington State
    Vehicle:
    2006 Prius
    Model:
    Two
    I will see if that has been done. That was done while my child had the car. I hope he remembers. He's not a paperwork guy.
     
    #42 frustratedInSeattle, Nov 11, 2025 at 9:50 PM
  3. frustratedInSeattle

    frustratedInSeattle New Member

    Joined:
    Saturday
    22
    1
    0
    Location:
    Washington State
    Vehicle:
    2006 Prius
    Model:
    Two
    The car drives very smoothly. Can I just add something to the fuel to clean the injectors? I always buy Top Tier gas.

    I sure hope I don't have a head gasket issue. That's a big expense. I will keep checking the coolant. Are there any other indicators of a head gasket issue?
     
    #43 frustratedInSeattle, Nov 11, 2025 at 9:53 PM
  4. JC91006

    JC91006 Senior Member

    Joined:
    Nov 10, 2013
    16,758
    8,562
    0
    Location:
    Los Angeles, CA
    Vehicle:
    2008 Prius
    Model:
    II
    I don't know if your injectors are a problem, just mentioning it "may" be a reason why your car is misfiring. But you say the car is running very smoothly so those codes might be history codes and not current codes.

    If you're happy about how it drives, then no need to do anything else to your car.
     
    #44 JC91006, Nov 11, 2025 at 9:58 PM
  5. frustratedInSeattle

    frustratedInSeattle New Member

    Joined:
    Saturday
    22
    1
    0
    Location:
    Washington State
    Vehicle:
    2006 Prius
    Model:
    Two
    OK, so I called the mechanic that just looked at the car, and he said "Well, there were like 20 codes, but I cleared them out before I took it for a [useless,10 minute] test drive. I didn't write down any of the codes before I cleared it."

    That's pretty annoying in my book, since he didn't even take it on the highway. I wish he had let me do it.

    But here are the remaining codes right now:

    Body control module
    P0420
    P0301 and P0304

    Note that these codes have probably been on since the original catalytic converter was stolen. The mechanic who replaced the converter said he couldn't figure out how to get rid of them. I re the O2 sensors,
     
    #45 frustratedInSeattle, Nov 11, 2025 at 11:22 PM
  6. PriusCamper

    PriusCamper Senior Member

    Joined:
    Mar 3, 2012
    12,633
    5,106
    0
    Location:
    Pacific Northwest, USA
    Vehicle:
    2007 Prius
    Model:
    Two
    Those aren't remaining codes, those are new codes... Gen2 Prius doesn't work like Gen3. The important issue is you have intermittent misfire in cylinder #1 and cylinder #4!!!!

    Either you're two quarts low in engine oil or you have bad coils or plugs or a failing engine... But based on the chaos of your approach to so many people trying to help and you dismissing them, I suggest you ignore the problem entirely and just enjoy your Prius until the issue gets worse.
     
    #46 PriusCamper, Nov 11, 2025 at 11:42 PM
(You must log in or sign up to post here.)
Page 3 of 3