Leaderboard

To check the lambda sensors you will need a code reader with live data. The sensor on the exhaust catalyst inlet (maybe listed something like lambda 1 or O2 bank 1) should be showing about 1.0 and switching continually up and down a bit if it is ok. The sensor after the catalyst (lambda 2 or 02 bank 2) should stay steady but if it switches similar to the inlet one it means the catalyst needs replacing. The sensors can not be cleaned but check the wiring and connectors in case these are at fault and not the sensor. Of the 2 sensors, the inlet one could affect performance since it continually adjusts the fuelling but the outlet one just checks if the catalyst is working. So if you need to replace a sensor it is likely to be the inlet one - beware that cheap copy sensors may not work as well as dealer parts.