Not too sure...have you definately got the correct engine group? The first couple i tried only gave 2 - 3 reads...done my own reading on the two values...calc is what the Ecu estimates which can vary alot depending on where/when driving. Due to my ratio of city driving I've done nearly 400 mins, but only 100km in the 10 days since my last run out, where it did a regen...which hopefully explains the disparity rather that sensor issues. I have an hours motorway drive tomorrow so I'll be interested to che k readings after...useful tool!