Emmissions system warning light coming on - what's the fault?

The emissions control system warning light keeps coming on when I drive my Audi A6. The lambda sensor has been replaced but the problem still persists. What could be the most likely cause? Also how much is the repair likely to cost?

Asked on 7 August 2013 by euan1982

Answered by Honest John
Probably the oxidising catalytic converter has failed. You'll be looking at about £500 to fix it.
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