I have a 2004 A4 Cabriolet with 32K miles. A month ago the check engine light
came when started one morning. The car runs fine. I purchased an OBDII code reader
and followed directions carefully, but when hooked up, it tells me no 'DTCs detected'.
I'm 'connected' to the on-board computer, recognized the protocal, etc. It's not an operator
error.
Hmm, called tech support and updated the reader to newest revision, etc., but still no
DTCs detected. I'm able to 'Erase/Reset' the codes which momentarily turns out the light, but
then comes right back on. Tech support was stumped.
Took it to a garage and they hooked up their reader with same result.

Has anybody ever seen this problem with not being able to read a code when 'Check Engine Light'
is on?

I've got an appointment with the dealer next week to have it looked at. Really hate spending $100
with no result. It's a good reader and is working properly.

 

What shop did you take it to? You have to get a code reader with a CAN bus ability.

 

Manual says it's compatible:
Links to all OBD2 protocols including CAN*

The reference is --> *NOTE: Feature was added to models sold after 1/1/06.

By the way, this unit was purchased brand new 10/15/07. It is not used.

I'll have to call tech support again tomorrow and make sure it is CAN compatible.

Thanks for the pointer......

 

hmmm, thats wierd. I say if you have no codes, then disconnect your battery for 10 minutes and then see if it goes away. It could be somthing as simple as your gas cap not being on correctly?

 

Make sure you have the radio codes.

 

Isn't your warranty still good? 2004 with 32K miles? If so, have the dealer figure it out.

 

yea howbout gascap last time you got gas??

 

Three year warranty ran out in June. Gas cap isn't the issue, and if it was, I would see a 'pending' code with reader.

Disconnecting battery. Hmm, I'll try this and make sure I have the radio code before doing it. Thanks for the pointer

Larry

 

Did the hard reset by disconnecting battery with no change. Check engine light is still there.
Strange thing is after having battery disconnected for 15 minutes, I didn't have to re-enter the
radio code. Hmm

Well, looks like it's off to the dealer on Monday. Disappointed

 

Ok, I've been through several hours of figuring out why a newly purchased INNOVA 3100a OBDII CAN (from Checker Auto)reader couldn't read a code when the Check Engine Light is on. After several calls to tech support, with no help, I took the car into Audi. They were able to read the code without trouble.

This is what the Audidealer found:

1 Trouble Code detected?
18201 P1793 000
Output Speed Sensor 2 Cir.
no signal
sporadic

The dealer told me this is coming from the transmission and would take a valve body replacement
to fix it. The car runs perfectly and suspect the sensor itself is faulty or wire loose. I was told you couldn't
just fix the sensor, they had to replace the valve body which meant dropping the transmission. Don't want to be cynical here, but I'm wondering about the logic of this. Anyway, looks like easy money for the dealer.

So I go home and look at the TEKLINK software that came with the reader.Included isa code library and see that P1xxx codes are not listed. Goes from P0xxx and jumps to P2xxx. I call tech support again and ask why it doesn't read this code? They said, "Oh, that's a transmission code and the reader doesn't read those codes". Why they didn't they tell me this in the first place, I have no idea. They said you'll have to buy a mulitple $K reader to do that. This reader is nearly useless to me. I suspect if you pay anything less than $400, you won't get the full code set. Just guessing. Disappointing experience.

Everybody suggests the VAG COM, which are severalhundred dollars and not sure I'm willingto invest that much at this point. Makes me wonder what'sNOTcovered by them also.

Frustrated with '04 A4 1.8T with 32K