[FRSBRZGT86FAN]

Originally Posted by ZionsWrath

Excuse the noob question, would I pass inspection with a tune that disables P0420?

I am stock tune/power got a random P0420 about a year ago. Cleared and never came back but just wondering in case it did.

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.

Originally Posted by ZionsWrath

hmm, would it cause any other readiness faults? Last I checked in NY we are allowed 1 unready code. Not sure if we are allowed 1 fail code though, I guess I got some research to do.

Steve99 is totally right. Dealers and mechanics in PA check for readiness with an OBD-II reader and test it with the engine at temp to make sure 1 can fail the others cannot, it fails if you get more than one unready. I'll be getting an OBD-II code reader soon that has emissions testing in it to double check but 1 will definitely show as not ready. It used to be that you could trick the readiness though in romraider with older wrx's . The only way to make sure everything shows ready is to do the spacer trick before inspections, or get one of those O2 sensor spacers instead of doing the DIY ([ame="http://www.amazon.com/gp/product/B00B1U6I54/ref=pd_lpo_sbs_dp_ss_2?pf_rd_p=1944687742&pf_rd_s= lpo-top-stripe-1&pf_rd_t=201&pf_rd_i=B00CZFCPQU&pf_rd_m=ATVPDKIKX 0DER&pf_rd_r=1EWB3BDPVS0ET9SE9Z95"]Amazon.com: 90 Degree Angled O2 Check Engine Light CEL Fix Oxygen Spacer Exhaust Extension: Automotive[/ame]) and tricking it into thinking the value on the second O2 sensor is lower than the first. Otherwise you'd have to put the stock header on for piece of mind.