mbob

How likely is it that the pre cats have failed? I really hope it isn't coz they cost a fortune Also is it possible to just gut the pre cats and re-weld without the ecu keep throwing codes and pass an emissions test?.... And will the thing distort after welding? Would replacing the main cat typically solve the p0420 code I got?

oh right so do you think it could be Leaking fuel injectors ,Clogged air filter ,Bad Mass Air Flow Meter or ???

ok so i was looking for info on the 02 sensors when i found this diagram turns out you can only get a p0420 on b1s2 . which is also the sensor i originally thought had a low reading so im guessing its probably what threw out the code. ordering a new one tonight but not sure what one to buy off ebay are all 3 sensors before the cat the same? or are they position specific?

So are these good enough results to rule out the cat itself? Also the car seems to be using alot of petrol 20mpg , the idle seems very slightly rough on first start up and it seems to take longer to start every time

ok lads thanks for the advice. ill try looking at the data whilst driving but the odb connection is right above the throttle kinda stupid place to put it the emissions for the last nct or mot which was only at the start of june were: at low idle : CO 0.18% (LIMIT IN IRELAND NOT ABOVE 0.50%) HC 38 PPM ( LIMIT N/A ) at high idle: lambda 1.01 (LIMIT IN IRELAND not between 0.97 and 1.03) 2500rpm CO 0.02 vol % (LIMIT IN IRELAND ABOVE 0.30%) HC 44 ppm ((LIMIT IN IRELAND NOT ABOVE 200 ppm) these seem like good enough results but i dont know much about emissions, ill jack up the car tonight and see if i can find any leaks i have since reset the MIL light and driven about 30miles and it hasnt come back on yet

hi all i recently bought a lexus is200 2002 with 75k on it i had a engine light come up on the dash scanned it and got dtc code P0420 (catalyst system efficiency below threshold) i looked at some live data while at idle with engine at operating temp results: 02 sensor 1 bank 1: 0.845 to 0.75 volts.... fuel trim 0 to +8% fluctuating 02 sensor 1 bank 2: 0.60 to 0.760 volts.....fuel trim -1.6 to +1.6 fluctuating 02 sensor 2 bank 1 0 .05 to 0.10 volts fluctuating no fuel trim info 02 sensor 2 bank 2 just said n/a are these normal results or is sensor 2 bank 1 broken or do i need a new cat?? thanks martin