Check Engine Light Due to Vacuum Leaks, Oxygen Sensor, or Catalytic Converter Fault on Audi TT Quattro

Problem Description and Possible Solution

Vacuum leaks, oxygen sensor failure, and catalytic converter efficiency faults can cause the Check Engine Light to illuminate.

Problem Data
RepairPal Verified
Average mileage: 92,956 (55,333–116,000)
Exhaust & Emissions affected: 1.8L 4 Cylinder Turbo
7 model years affected: 2000, 2001, 2002, 2003, more2004, 2005, 2006
25 people reported this problem
Viewing 1 - 9 of 9 comments
Check engine light will not stay off, says it is the O2 Swnsor. Replaced it and now its back on..Frustrated.
Appears to be the caused by the failure of the air pump and air valve. Apparently a common problem as I have a friend with a simliar age TT that has the same issue. The pump keeps the fuel tank pressurized so if it fails the diagnostic system thinks there is a vacuum leak.The car will fail an emisions test, but the car is still usable until you can get it fixed. Cost is around $800.
I have had my car in the shop several times due to Vacuum leaks, oxygen sensor failure, and catalytic converter efficiency faults that cause the Check Engine Light to illuminate, to the tune of approximately $1500 over the past year. Both repairs were made between 90-95K miles(currently has 96K miles). Now I'm looking at possible modulator failure. Doors won't lock, inside lights don't work, convertible top doesn't work, and car doesn't recognize key remote! Air bag light is on also???
Mi carro lo prende y sales al rato se a paga y no lo puedo arrancar por una hora
Code 1136 lean mixture in bank1
Mostly the hard plastic vacuum pipes splitting at the ends where they fit over something else. Various locations.
same problem replaced one cat. converter twice 1st one failed. still coulden't get pass from DEQ, changed out oxygen sensor and made it through. but have still hava problems with engine light.
engine light on. shop says maf sensor problem
replace o2 sensor