View Full Version : Unable to scan car with VAG... help!!

09-22-2006, 09:03 AM
My sister has a 98 B5 passat and had her check engine light come on - no big deal, right? Wrong. So I bring my vag cable over to her house with my laptop, plug it in.... and nothing. The computer thinks that the cable isnt plugged into anything at the opposite end. I then plugged it into my A4, bam, it works like a champ. We took the car to Autozone and their scanner wouldnt work either! Any ideas as to why her car is not showing up? Does the OBDII connector on the car have some sort of fuse that may be blown? Thats the only thing I could think of, but I dont have an instruction manual for her car so Im unsure where to look. Any ideas or comments would be great... thanks!

If it matters, she has the 1.8T (which Im not too familiar with since my A4 is a 3.0)

09-22-2006, 10:01 AM
i had that too and the ecu was bad. not saying thats the problem but thats what happen to me.

09-22-2006, 11:26 AM
Try unplugging the ABS control module

09-22-2006, 11:52 AM
I've had that before, tried it with another VAG and it worked...

09-22-2006, 09:57 PM
Had the same problem with my 01 A4.....ended up the ECU was dead.

09-23-2006, 03:14 AM
Besides the check engine light being on, does her car still run? If so, I doubt the ECU is bad. What VAG cable do you have? I know I've read somewhere that some cables don't seat properly in the plug causing it not to be recognized by the ECU (and vice versa). You may want to research this a bit. You might try removing the car's ecu harness from the kicker panel and plugging it in that way (a better fit).

09-23-2006, 07:01 AM
Isn't there something that if you have an aftermarket radio that VAG won't work correctly? I know you can have some type of problems if you have an aftermarket radio...

09-23-2006, 08:53 AM
all excellent ideas! How do I know if the ecu is dead if the VAG wont scan and the car still runs? Doesnt make a lot of sense to me!

I may take baldies idea of unplugging the ecu's harness from the panel... anyone have a decent pic I can see of the area with the ecu exposed? As I said, this is in a 1.8 and Im not at all familiar with any aspects of it... so consider me a noob!

09-23-2006, 09:17 AM
The VAG bus and the engine functions are all on different portions of the ECU... Therefore you can have a dead VAG bus but still have your engine work fine...

09-23-2006, 10:18 AM
Take off the knee bolster where the OBD port is located and check to make sure it's actually plugged in.

09-23-2006, 12:12 PM
Sometimes the K-Line can get damaged in these cars if you have aftermarktet electronics installed. Check everything from the ECU to the VAG port.

09-23-2006, 07:57 PM
thanks, I will check all that out next time she brings her car over....

09-24-2006, 09:51 AM
i know on mine in the back seat there is a port you can plug into on the bottom/back of the console.

09-24-2006, 05:47 PM
^ what? can you take/post a pic??