Catless UEL + Tune...Still Get P0420

[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.

[Michael]

A little update on this issue. The guy bought a new cable and had no issues connecting to the ECU. I had him flash it back to stock so that I could be done with his inability to disable the P0420 code. I have just updated my OFT and flashed to the Stage 2 UEL 93 tune and will see how that works out. I will try to datalog when I can soon to check the data, get some input from you all and learn as I go.

[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?

[2016 Camaro SS]

I flashed my stock tune on my FR-S, drove to get an inspection, flashed my tune back on. This was with a catless header and catted front pipe. Drive was maybe 10 minutes to the inspection place. Passed with no issues. Just a really underwhelming performing car on the trip there and back.

[steve99]

Originally Posted by SUB-FT86

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

quite possible you could pass, but im not 100%, our firmware in ECU is different here so I cannot check how many redyness tests fail for you.


If you have android torque app on phone/tablet and a $10 elm327 Bluetooth adapter you can run readiness checks yourself