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2020 Prime shows Check Engine but cheap OBDII says "no codes".

Discussion in 'Prime Care, Maintenance and Troubleshooting' started by The Big Sleaze, May 30, 2024.

  1. The Big Sleaze

    The Big Sleaze Member

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    Do I need a better ($$$) OBDII reader?

    Recently had 12v batt go low for no real reason (left lights on a few months ago for like 15 minutes, had to get jump, then didn't leave anything on but next morning got a Low Battery, and also a "Error in lane assistant" but that went away after a drive and restart.

    Car has about 97,000, still on 1st factory set of plugs, brake pads, etc. Only changed oil, coolant, ATF, oil and air filters. This is first time Check Engine has come on.

    Also has "see dealer for service" which I guess is just oil change reminder.

    Any way to dig into system from dash video screen to see what Check Engine is all about?
     
    #1 The Big Sleaze, May 30, 2024
  2. Brian1954

    Brian1954 Senior Member

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    Yes, you need a better scan tool. Take a look at this thread:https://priuschat.com/index.php?posts/3290690
    The Autel AP200 is a good choice and costs about $60 ON Amazon.
     
    #2 Brian1954, May 30, 2024
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  3. The Big Sleaze

    The Big Sleaze Member

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    thx, ordered. But I'm a bit miffed that a Govt mandated system like OBD II doesn't require that The System can't at least spit out codes to a basic OBD II reader, and in this day of EVERY car having a computer screen on the dash, doesn't give codes and likely meaning, with I guess a few legal CYA about "don't try this at home, go to dealer".
     
    #3 The Big Sleaze, May 31, 2024
  4. FuelMiser

    FuelMiser Senior Member

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    No, an OBD II code reader is the only way. Is the CEL still on when you are reading the codes? If it went out, then the code could have cleared itself. CEL is a minor inconvenience, may only effect MPG, if anything at all. It signals issues with the emissions (catalytic converter, O2 sensor) and fuel vapor control systems. You can drive with CEL, but not pass emissions tests, if your state requires them.
     
    #4 FuelMiser, May 31, 2024
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  5. BiomedO1

    BiomedO1 Senior Member

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    This simply feeds into the "right to repair" issue and propriety knowledge arguments. OBD II codes are generic in nature to follow the letter of the mandated law from decades ago. It's up to the OEM to release more information than mandated.
     
    #5 BiomedO1, May 31, 2024
  6. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    Technically, it does.

    If the code your car has presented is one of the ratified SAE codes covered under the law, it will be readable by any generic reader.

    Since you have a maintenance indicator lamp on but your reader can't see the code, chances are the code has nothing to do with fuel injection, emissions, ignition, or the other basic-basic stuff covered by that law.
     
    #6 Leadfoot J. McCoalroller, May 31, 2024
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  7. The Big Sleaze

    The Big Sleaze Member

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    thx, it also flashed something about "lane assist error" but that went away, and now the Check Engine light is also off.
    Autel AP200 shows "faults" but not codes. Can I get more specific CODES for this stuff out of Autel AP200?

    2 ABS/VSC/TRAC Fault | 1
    14 LKA/LDA Fault | 1
    16 Air conditioner Fault | 1
    26 HI autoleveling Fault | 1
    27 Smart key Fault | 2
    28 Power source Control Fault | 1
    30 Navigation system Fault | 3

    Don't know what LKA/LDA mean "lane departure assist" ??? Don't know "HI autoleveling".

    Everything seems fine and car drive perfect.

    I'm thinking (praying) all this was caused by my Low 12V event, and just stayed in system as "flags", but all I need to do is hit "Quick erase" on my Autel Ap200 and everything SHOULD clear and stay cleared, until next time I run the 12V low. Seems like this is all stuff that is pretty much 12V systems. Haven't "torture tested" the ABS/VSC/TRAC, and not even sure what a failed TRAC would feel like.

    Should I hit "Quick erase" and then check in a day after some driving?

    I've got the basic "LE" model and don't use any of the onboard Nav, etc.
     
    #7 The Big Sleaze, Jun 1, 2024
  8. The Big Sleaze

    The Big Sleaze Member

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    I once blew out a $2000 Cat Converter on a big Chevy Van due to driving with a plug wire that got fired on the exhaust manifold. Kept driving the thing for far too long before fixing. So I'm once bit and twice shy about any CEL.
     
    #8 The Big Sleaze, Jun 1, 2024
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  9. Brian1954

    Brian1954 Senior Member

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    Do not clear the codes. I have not used the AP200, but you should be able to scroll or click on the different ECUs listed to see the trouble codes detected. Maybe someone who has used this scanner can give you detailed instructions.

    Edit: Maybe search online for a video that shows the Autel AP200 being used on a car.
     
    #9 Brian1954, Jun 1, 2024
    Last edited: Jun 1, 2024
  10. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    I don't clear codes without first recording them somewhere else.

    Once I've got a record that I can refer to later, I usually feel free to clear what's there and then see if there is a recurrence.

    The Autel maxi app will show the actual fault codes. I can't remember where to tap, but I did get it to show them.
     
    #10 Leadfoot J. McCoalroller, Jun 2, 2024
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  11. The Big Sleaze

    The Big Sleaze Member

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    got Autel to kick out actual codes:

    examples:
    TCS/ABS etc C1247 "Hi or Low power volts"

    A/C U0163 "Lost Communication with Navigation Control Module" (Wth does A/C need to talk to "NCM"?)

    But all sounds like related to my low 12V event.

    Try to erase but Autel asks me "Is ignition on and engine off?" but how does that work on a Prius Prime? Even if ICE is not running, the "engine is on" in a way. Tried doing an Erase but all the codes came back. Next plan is to disconnect the 12V for a 1/2 hour or so, then see if codes are still there. But I'm guessing a 2020 Prime will have a way to remember all that stuff, like when you take battery out of a phone it still retains everything.
     
    #11 The Big Sleaze, Jun 2, 2024
  12. Danno5060

    Danno5060 Active Member

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    Just like when you drive it, treat "Ready" as if the engine were running. Like you do when the light turns green - push on the gas pedal and drive, whether the engine is running or not.

    As to the rest of it, it's not just one ECU, but dozens of controllers all "flying in formation" to control the various systems of the car. Most of the low-end scantools just read the main engine ECU, so one of the other controllers could have issues that are not going to register on the engine controller.
     
    #12 Danno5060, Jun 3, 2024
  13. The Big Sleaze

    The Big Sleaze Member

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    So does a Prius have any "ignition on, engine off" mode as far as getting a OBD II scanner to Clear Codes? IIRC "key detected in car" is same as "off" on Autel. MAYBE the manual old style physical key override? Never tried it, maybe that is next.
     
    #13 The Big Sleaze, Jun 3, 2024
  14. BiomedO1

    BiomedO1 Senior Member

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    yes; don't hit the brakes when you turn it on - accessory mode....
     
    #14 BiomedO1, Jun 3, 2024
  15. FuelMiser

    FuelMiser Senior Member

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    There's actually two modes the car can be in if you don't press the Brake Pedal when pressing Power: 1) first push puts it in Accessory Mode, 2) second push puts it in Ignition On. You will not be in Ready, but all ignition systems are powered by the 12V. Thus, do not leave it there for very long or risk running down the 12V.
     
    #15 FuelMiser, Jun 4, 2024
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