The diagnostic socket is at the lower edge of the dashboard on the driver's side.
expand_moreIdling speed with automatic gearbox
expand_moreIdling speed with manual gearbox
expand_moreAll other modifications
AJQ engine
640–920 rpm640–920 rpm640–920 rpm
APP engine
700–820 rpm700–820 rpm700–820 rpm
AUQ engine
640–840 rpm640–840 rpm640–840 rpm
Minimum engine oil temperature at VET
176°F176°F80°C
expand_morePetrol exhaust gas values
CO content at idling speed
0–0.5 %0–0.5 %0–0.5 %
CO content at increased idling speed
0–0.3 %0–0.3 %0–0.3 %
expand_moreIncreased idling speed
expand_moreAll other modifications
AUQ engine
2500–3000 rpm2500–3000 rpm2500–3000 rpm
Otherwise
2500–2800 rpm2500–2800 rpm2500–2800 rpm
expand_moreLambda sensor design
expand_moreAll other modifications
AUQ engine
wideband sensor
Lambda value
0.97–1.03 λ0.97–1.03 λ0.97–1.03 λ
Maximum HC content at idling
70 ppm70 ppm70 ppm
expand_morePetrol conditioning speed
All other modifications
2500–3000 rpm2500–3000 rpm2500–3000 rpm
Petrol conditioning time
120 s120 s120 s
expand_moreTest speed for lambda sensor signal
expand_moreAll other modifications
AUQ engine
640–840 rpm640–840 rpm640–840 rpm
To reduce environment impact and pass government inspections keep emission parameters at the level prescribed by Audi.
Please be noted that all capacities listed here are approximate. Check fluid levels when adding or refilling as recommended in your 1999 Audi TT user's manual. Keep in mind that all information here is provided “as is” without any warranty of any kind.
Before doing any DIY service please check your insurance policy and Audi warranty policy for your region. In some regions DIY service may invalidate your warranty.
DIY car service is not as difficult as it looks like and it might save you thousands of dollars per year. It might be even fun and a good thing to do with your kids on a weekend to teach them how basic machinery works. It's really hard to screw something up and damage your car permanently if you use right tools, follow Audi TT service manual and use right parts and fluids in prescribed amounts. Even modern cars stuffed with electronics can be serviced in your garage or even in your driveway. Changing engine oil, brake fluid, ATF, replacing brake pads, and etc. It's all may be done by yourself in a mater of a couple of hours.
Doing basic service for your 1999 Audi TT you're not only saving money, but also also improving your technical skills and learning something new.