Anonymous
Anonymous asked in Cars & TransportationMaintenance & Repairs · 1 month ago

What exactly should I be looking for with an OBD2 scanner when buying a used car?

I am planning on buying my first car sometime this summer, and I have been doing a lot of research on how to buy a used car. I was watching a youtuber called ChrisFix, and he recommends a OBD2 scanner, however, he never really went into detail on how to use it and what the codes actually mean.

What exactly should I be looking for with an OBD2 scanner when the results come back up? Would it be better to just take it to a mechanic to do the OBD2 scan results before I buy the car?

12 Answers

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  • 1 month ago

    You don't need an OBD II code reader to buy a used car. When you start the motor the CEL needs to turn off or just don't buy the vehicle! Most used car lots will erase the codes to turn the CEL out. After 3 key cycles the CEL will come back on if there were codes to begin with. Go for a test drive and shut the motor off for a minute after driving a couple of miles each time. That should make the CEL come back on if the codes were erased. The most common reason they erase the codes is a P0420 code relating to a bad catalytic converter!

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  • not
    Lv 7
    1 month ago

    An obd2 scanner will gain you access to the engine computer. No codes stored and all monitors run is what you can look for there. A real scan tool could check all the other control modules and see if there are issues in other areas, function test things and a relative compression test even. You'll want to raise the car on a hoist too; check for rust, accident damage, leaks, suspension wear. 

    Do consider a profession inspection. I've offered to do used car inspections for free for some people. They don't do it and then I see them two weeks later with their "new" car and expensive problems. 

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  • 1 month ago

    You should be looking for NO codes, and 'ready' status on all monitors.

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  • Anonymous
    1 month ago

    You are buying your first car?  Get someone who knows about cars to go with you.  The codes can be cleared so checking for codes is a worthless test.  The only check you really need to do with a scanner is that the scanner can "communicate" with the car's computer.  If the scanner cannot detect the car's computer or cannot "communicate" with it, do NOT buy the car.  A cheapo scanner is all you need for that communication check.

    The car has to be test driven and given an inspection by someone who knows cars.  If your state requires a smog test, get the seller to give you a smog test before buying one.

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  • 1 month ago

    Codes will only tell you so much.  A good mechanic could save you a lot of heartache.  Have the car checked out before you buy it.

    https://youtu.be/RLOpo71JtIU

    Youtube thumbnail

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  • Anonymous
    1 month ago

    Any active trouble codes  and any PIDs that show NOT READY status indicating the codes have been recently cleared.

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  • Dan
    Lv 5
    1 month ago

    A cheap scanner is handy to have. The single thing biggest thing you should look for when buying a used car is the readiness monitors. If the seller has recently cleared the codes to make the car look good to the seller the emission readiness tests may not have run yet. If all the monitors have run and no codes have set then the car should pass an emission test and the engine is probably in good shape.

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  • Joe
    Lv 7
    1 month ago

    You'll probably find the instructions on how to display stored codes first.

    Dig a little deeper in the instructions, and learn how to determine if the monitors are "ready".  (The terminology might have changed.)

    Remember that not every car will have all the monitors.  BUT: if you plug in your reader, and a lot of the monitors say "not ready" (instead of "ready", or "not present"), that's a BIG RED FLAG.  It means that the seller has cleared the trouble codes to turn off the Check Engine light.  The seller is hiding something.  Walk away.

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  • Ron
    Lv 7
    1 month ago

    How to use it? You follow the instructions that come with it. Then you google the code numbers and discover that at least 6 different things can cause that code. Then you go back to his channel and hope he has one that tells you how to diagnose those problems

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  • Rick
    Lv 4
    1 month ago

    The specs have changed over the years, so make sure you get one that does the year of your car .................

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