[SUB-FT86]

Originally Posted by steve99

Im not 100% on all the different checks done in USA and different states etc.


disabling P0420 stop the cel light and stops the ECU taking the action it would normally take when it detects that CEL code which is disabling Cruise control.


However the ECU still does its calculations comparing the front and rear 02 sensor reading, it just does not act on the P0420 code if you disable it, and it wont log the code in ecu memory.


However the ECU also does other checks called "readiness" checks, these will still show "fail or incomplete" on catalyst system if they do "readiness checks"


Some states may only do visual, some may just check for CEL codes but if they do "readiness checks" then you will still fail. Readyness test are done constantly by ECU and the inspector will just plug in and interrogate ecu for the data. Failed readiness checks don't light CEL.


you can interrogate ecu yourself with something like the Android Torque app and monitor CELs ,stored cels and readiness check monitors.


When you reset the ecu the readiness check all set to fail I believe then over time they will come good if the ecu sees the correct inputs this can take an hour or so of driving to get all the readiness checks to pass.


not even Ecutek forces readiness check to PASS, it probably due legal reasons not sure.

My state does readiness checks but you can pass with 1 not ready. Would I fail with the UEL header/OP and tune?