Question about 1998 Audi A4

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I just replaced the engine (AHA) in a 1998 A4. It runs good now and has a slight misfire, however, when I plug my snap-on scanner to the car, there is no communication with the ECM. There IS power at the obd2 plug and the fuse is ggod.

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  • ratatat1975 Dec 19, 2008

    Thanks for the reply.

    I used a CAN-capable global scanner, and when that one didn't work, I used a Snap-on MT-2500 with the Audi/VW specific card and connector. The OBD fuse is good and both scanners power up when plugged in but won't communuicate. I replaced the AHA engine with one out of the junkyard due to a broken timing belt tensioner and also replaced the throttle cable, and starter. The newer engine now has a slight misfire, check engine light is on, and neither scanner will communicate with the ECM. The ECM is the origional one. Also replaced, battery, plugs and wires, oil, fuel and air filter, and crankcase vent piping. Any suggestions? One guy said the ECM may be in "Lock-Mode"? Does this sound right?

  • Jeremy Kastrup May 11, 2010

    are you using global OBD or Vin Entry ?



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I don't believe it's in "LOCK MODE" as if you removed the battery it would do the same thing as removing the engine. I would start with checking fuel spark and compression in all cylinders , a weak coil would give you a missfire , also the wrong/worn spark plugs can make an engine misfire when doing a compression test get the values of each cylinder and see if one is lower than the rest.

Posted on Dec 19, 2008


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