The Malfunction Indicator Light (MIL/Check Engine Light) in my 1997 Audi Quattro Wagon has been triggered. According to the Owner's Manual (Audi A6/A6 quattro, Nordamerika, englisch 7.96, 971.561.4A0.21) on page 67 & 68, two things could be happening. 1) Emission control system malfunction, 2) Speed limiter malfunction.

According to the owners' manual, the on-board diagnostic system should register a code in the control unit's memory if the emissions system has malfunctioned, but the manual does not state if a code will be registered due to a speed limiter malfunction. I have checked for codes with my OBDII code reader (Codekey model 375265 from JS Products, Inc.) and no codes are detected.

Some background information: Last month, my Audi would die at stop lights, but the MIL was not being triggered and no codes were registered so I had Audi check the car. After they cleaned the ICV (Idle control valve), Throttle pipe and readjusted the throttle switch, the car not only stopped quitting at stop lights, it also performed better and responded with more power. It wasn't until two weeks after Audi fixed the stop light issue that the MIL was illuminated.

Has any one encountered a situation like this, or does anyone know what else would trigger the MIL without registering a code in the control unit's memory?

The car is running great and only has 80K miles on the odometer, but driving around with the MIL illuminated is not very reassuring. Thanks in advance for any light you can shed on the issue.

 

If it is the CEL there should be a code. Get a VagCom and see what it says. Audi is not truly OBDII. do a search in this section for RossTech and VagCom to see what options you have -- the cheep Ebay cable and free software seems to work well for most people.

 

Your OBDII code reader is unable to read the special Audi error code which is causing the MIL. Try www.ross-tech.com .
Also, check to see if all of the emission monitors have reset.

 

Ok, thank you both for the information.

 

Allright, so the code I have is " P1423 Bank1 Airflow To Low ". Time to do some research!.

 

Common problem --Check the vacuum lines around the combi valves -- Do a search on this forum for info there are a ton of posts that explain the fix.

 

Well I just got back from my dads house ( he has a lot more tools than I do so I decided to work on my A6 there ) and everything turned out pretty good. I changed about 80% of my vacuum lines...reset my MIL with my code reader and then headed home. The MIL didn't come back on after the 25 mile drive back but we will see if it does later on.

While I was replacing all the vacuum lines I had decided to clean out the bank 1 EGR valve (combi valve) but after removing the hose to it and looking inside I found that it was clean as a whistle. I did not remove it and look at the bottom hose however ( I suspect thats where the carbon build up would be if there was some?)because I don't have a replacement gasket and I'm assuming id need to replace it after doing so.

I took some pictures with my dads camera but I forgot the bring it back home...ill get it tomm or the next day and post some pictures. When I was changing out some of the vacuum hoses I ran across a little blue valve connecting two vacuum hoses, I took a picture of it but does anyone know what it is and what it does?

Thanks for all your help.

 

Alright, I got the pictures.

Some of my hoses were in pretty bad shape.


I was in a little bit of a hurry...sorry for the bad pics lol


In the middle of the top black hose it was definitely cracked in half.


EGR valve/combi valve


valve cover recirculating hose? I cleaned it out with carb cleaner.


And I found out that the blue valve was the EGR Frequency Valve.