Catless UEL + Tune...Still Get P0420
 

I recently installed my Gruppe-S UEL catless header, Invidia over pipe, Berk HFC front pipe, and Perrin resonated 2.5" catback system. Shortly thereafter, I had my car tuned and I was on my merry little way. Since I do a lot of interstate driving, the P0420 code popped up quite quickly and with that, I lost cruise control and when I slow down to 11 MPH, a slight jerking motion probably from it automatically downshifting with that code on (I haven't tried to downshift manually yet to see if that jerk is present that way).

I took it back to the tuner and the night before I did, the CEL went away and cruise control was back. Nonetheless, he checked over the tune and reflashed the ECU. Well, the code keeps coming back and then disappearing after a little bit more driving. I informed the tuner about this issue and he is doing his research with some connections that he has.

My question is this...is it possible to permanently have the system IGNORE the P0420 code so that I do not lose cruise control? With having RLS (restless leg syndrome), my leg tends to become quite uncomfortable just pressing and holding on the gas pedal for long trips unless I am constantly shifting my leg and foot placement.

looks like tuner forgot to disable P0420 cel code its just a single check box in romraider or ecutek

I will send him a message to see about disabling it. I cannot recall if he said he did or if he just cleared the code.

If you've been there twice and he hasn't disabled it, he's useless.

This tuner doesn't know what he or she is doing.

I've had P0420 disabled for close to 2 years now and I'm on cruise control from LA to Austin TX right now.

-alex

So I got a message back from the tuner and he said that he has disabled it via the checkbox and is not sure why it is coming back on still afterwards. He said that he will get back to me after he contacts some folks at ECU Flash about this issue. Does anyone have experience with ECU flash? Is it comparable to using another tuning option? Should I look elsewhere?

Sorry man but I'm calling bs. I think he realized that he forgot to turn it off. He will 'call' the other owners who won't have that problem. He will call you back and say 'nope none of them have a cel, why don't you come back in and I will reflash the ecu...' But this time the code will be turned off. Is this with ecutek?

Hopefully this is sorted out for you soon :)

use tactrix ecuflash quite a bit.

its likly a problem with the definition for the particular rom

if the guy is flashing oft romns with ecu flash hes probably been caught with the rom calid changes if so you quite lucky the ecu int bricked.

get him to open rom in romraider using romraider defs

if you post thge rom up here we can have a look

Or just buy your own tactrix adapter and fix your own problems. They're super cheap. Much less painful than going back to your amateur tuner.

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.

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.

nailed it

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.

While this is something that I would like to do eventually in learning how to tune my car myself, I do not want to mess anything up without some practice/teaching.