SEAT TOLEDO 2003

Hello everyone... I just bought a 2003 Seat Toledo 1.8 20V... Can anyone tell me about this car? It has 125,000 km but it's really in very good condition... except I haven't been able to turn off the check engine light, which is on in yellow... The seller told me it's because he removed the catalytic converter... My question is, I haven't been able to verify this since they haven't been able to access the engine with computerized diagnostics... Why is this? Has anyone else had the same problem? Greetings,
Nikitim