How can I get my Peugeot 307 through its MoT? It's failed on emissions.

My Peugeot 307 1.6 diesel has just failed the MoT on emissions. There are no warnings on the dash and my mechanic is unsure of where to start to fix the problem. The average smoke reading is 3.28 (pass is 3.00) with a high of 3.81 and a low of 1.91. Any advice would be gratefully received.

Asked on 31 August 2010 by Mirage150

Answered by Alan Ross
You have a exhaust oxygen sensor fitted to your car, somewhere in the exhaust system. This senses the amount of oxygen in the exhaust and sends a signal to the ECU (engine management system), which then regulates the amount of fuel being delivered to the engine, thereby achieving the correct exhaust reading.

There may be a number of things that have caused this problem. The catalytic convertor may have failed, there could be a fault in the ECU or with the exhaust sensor, or it may be something as simple as a blocked air filter.
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