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

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: 74,598 (31,000–131,000)
Exhaust & Emissions affected: 1.8L 4 Cylinder Turbo
7 model years affected: 2000, 2001, 2002, 2003, more2004, 2005, 2006
19 people reported this problem
Viewing 1 - 6 of 6 comments
eplaced the oxygen sensor and the light came back on. The mechanic now says that it is a computer failure
Engine check light on. Audi review noted oxygen sensor, another auto repair mentioned it may be some else which caused this to happen. Review turned up nothing. I now want an dedicated audi TT repair location other than the dealer to check problem. Any suggestions.
CEL on, replaced MAF CEL back on two days later! Common in German cars, same problem with Mercedes SLK 230 Kompressor. Never resolved after multiple repairs.
Chk Engine Light--had faults for catalyst and coolant system performance. Quoted repair $500 for thermostat replacement.