For owners of 1.5 & 1.3 Sirion 2008 and 2005 onwards respectively, I have found some cheap lambda sensors that match Original Equipment Manufacturers (OEM). The problem has been cross-referencing the original part numbers but it appears Denso have had an update on the catalogue.

The pre cat. Daihatsu number is 89465-B1040, which translates to a DOX-0113. The post cat Daihatsu number is 89465-B1020, which translates to a DOX-0236.

Taking those numbers to this website http://www.sparkplugs.co.uk/ they are a very good price - the cheapest I have seen anywhere. The DOX-0113 is £34.50 and the DOX-0236 is £48.00. Bearing in mind that OEM ones cost £300 this is very good news.

I advocate changing these sensors long before they fail. At this price I will be changing mine on the same periodicity as my Iridium spark plugs - 50,000 miles. I can't stress how much of a difference new lambda sensors will make to your driving experience - more go and less fuel. I promise.

Regards