Hi all, The above vehicle logged P0420 - Cat system efficiency below threshold, bank 1. I have checked the pre and post cat O2S and both appear to respond quickly to forced air leak or enrichment. Gases at 2500 rpm are CO 0.00%, HC's 6ppm, CO2 15.02% O2 0.04%, Lambda 1.002. I can't see anything wrong there. LFT is -3.1%. I have attached a couple of pics of the sensors and it would appear that the post cat sensor wont stay still. I am very loathe to condem the cat on this vehicle taking into account the gas readings. After I cleared the code it has not returned but it has not had much of a drive since then. the first two pics are 2500 rpm and the second two are at idle.
Any suggestions or previous experience will be most appreciated. Many thanks, Bryan.