obd2 port Doesn't work?

So i've been trying to get the obd2 to work on my 04 silverado. the scanner doesn't use batteries, and it turns on when i plug it in, so i'm pretty sure it's getting power, but whenever i try to read codes, it says "communication error". i've gotten it too work in the past by fiddling with the connector enough, but today it just wouldn't work. I also checked all the pins on the connectors, and they all look good. I've also tried testing it on a different vehicle, an 04 sierra, and it did the same thing. all the other vehicles i've tried have worked fine.


I've gotten it to work in the past, so i'm pretty sure it's compatible. 

Update 2:

So today i got both of them to work. Apparently the engine has to be running for it to work. That's probably what made it work last time. Anyways both trucks had an "evap system test failed". Kinda weird.

5 Answers

  • 1 month ago

    The scanner needs a new cord. Just saw your updates; Good you tried with the engine running. I never had a code scanner work that way. If that's the case with GM vehicles, I'm glad to know that too.

  • L.N.
    Lv 7
    1 month ago

    See if there are any software updates available for your scanner. Not unusual to find that a particular scanner does not work on some specific vehicles, but they can be fixed by the manufacturer of the scanner with firmware updates in a lot of cases.

  • Erik
    Lv 7
    1 month ago

    Go to an auto parts store and use their scanner, it's free.

  • Anonymous
    1 month ago

    Turn key to ON/Run (do not start) and check if the Check Engine Light is ON.  If it is not, there is a problem with the ECU.  If the Check Engine Light is on, get another scanner.  The scanner connector likely finally failed.

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  • 1 month ago

    Try a different cable before buying a new unit for you said you wiggled the cable and got it working it got to be the cable's contacts or dirty, wore out or whatever.....believe me, cables that get plug in and out in our technology world is a weak point........ 

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