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Hi Guys, Wonder if you could help, I have got the EML now being displayed on the dash. Have code read the fault and it has come back with P0420 'Catalyst System Efficiency Below Threshold Bank 1'. I know that this code can be triggered by many things such as an air leak in the exhaust, lambda sensors (but usually P01?? code is usually triggered) I have read the freeze frame data but im wondering if there is anyone that could understand the data more than what I can. From what I've read up on, the SHORTFT and LONGFT should be as close to 0 as possible. However from the freeze frame data you can see that the SHORTFT has a positive reading and the LONGFT has a negative reading where its trying to compansate and correct the fuel mixture. What I am wondering is, from this freeze frame data, could someone diagnose where for me to start replacing parts. I'm hoping that this is just a lamda sensor issue, I have already replaced the pre cat lamda sensor on Bank 1 (Denso part no DOX-0236). Without this help, my next step would have been to replace the lamda sensor by the main cat (not sure of the Denso part number for post cat sensor), so that bank 1 has had a replacement sensor before and after the cat, to see if this clears the code. I know that I might need to replace the cat, but at this moment in time I am trying the cheapest option first to resolve the issue. But all of your opinions are welcome. Here's the freeze frame data: Other data from code reader: I hope someone on this site can point me in the right direction. Many thanks, Dean