Question about 2000 Volkswagen Jetta TDI

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Jetta failing smog due to non communication with OBD - Suggestions?

I recently took my 2000 Jetta into two different smog shops and failed both due to "no data from pcm - OB II failed test" and "vehicle failed the MIL/Check Engine Light Test due to OBD Communication Failure". My check engine light isn't and hasn't been on and the bulb isn't burnt out. The mechanic says the computer is reading my stereo as an after market, but it's a stock stereo. They both recommend I take to the dealership, which I know is going to cost a lot just to run a diagnostic. Last time I had it smogged, it passed fine and I haven't changed any equipment since. Anyone have suggestions on how I can pass my smog and what the issue may be? Thanks!

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  • rlcrumley Oct 01, 2008

    There is a known problem about Jetta radios. I had a JVC aftermarket radio put in my 1999 Jetta, to get a CD player which the VW radio original didn't have. Then it couldn't pass smog. I was told that the radio power is somehow wired into the car's computer system, and that I'd have to replace the original VW radio, get the car smogged, and then replace the aftermarket JVC radio. (all of which I did.) the car passed smog certification (CAL). I have since learned that the technician has to KNOW about the problem, when wiring an aftermarket radio up, to avoid this "glitch" / "tilt" in the computer system for smog certification

  • randombob11 Mar 22, 2009

    Anyone heard of this happening to a 1995 passat gls? This thing will not pass smog. The tech told me that the engine is getting too much fuel and also blowing too much co2? HELP

  • Anonymous Apr 08, 2009

    i got the same problem and i dont know wath to do ? i got a passat 1998 OBD communications failure yestarday


  • Anonymous Mar 16, 2014

    the engine idles a litte ruff and when I try to get it smogged it fails the NO is to high at 627 there is no check engine light on.

  • Anonymous Mar 23, 2014

    is it ox senor or something else

  • Anonymous Mar 28, 2014

    Put a new battery in my Jetta TDI a month ago, yesterday took for california smog check and computer showed as failed on 2 of the 3 things checked, fuel system was runs great over 50 mpg, but failed smog check because of computer...any ideas?

  • Anonymous Mar 31, 2014

    My 06 jetta TDI failed the CA smog check this morning, due to "smoke" coming out of the exhaust. Is this due to the car not being warmed up/purged prior, or is there another fix i'm not aware of? The engine has 270k miles on that part of the issue?


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The no data error can be contributed to a bad interface cable or the scaqn tool was configured wrong and therfore could not connect to the ecm. I would recommend having a scan done again by a certiefied volkswagon tech chances are the mechanics used the wrong adapter cable or reader card. your smog problem could be that your evap canister is clogged therfore gives a bad reading.unfortunately you have to have a scan done but try an independant small shop that delas exclusively with foreign cars such as porche andd mercedez. the will have the correct scan tool and will be much cheaper than a dealership. your cost should be no more than 50 dollars US ... please rate this. thanks

Posted on Sep 23, 2008

  • wilmerrizald Dec 05, 2010

    1998 Vw Golf 2.0L communication failed, i recently bought this car and no check engine light on when i turn the engine no signal coming from ECU to s smog machine. Anybody knows what causes the problem?


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Posted on Jan 18, 2011

  • George Kline Feb 10, 2011

    The Problem is with what is called the K-line. You can do a search for the K-line fix cut it out of the aftermarket harness and then everything will work fine. If you are in a Pinch you can just pull the radio unplug it and that will take care of the OBD2 communication problem on most vehicles for now and do the fix later. Remember this isn't just a smog issue. Anytime you need to have the car scanned for a check engine light NO SCANNER is going to connect as long as that wire is grounded out


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