p0420 code, help
 

I have a ZZP DP with high flow cat. I have had this set up for about three months, no problems. three days ago, I start getting the CEL p0420, catalytic insufficiency. the only thing i have changed since the DP install is a coolingmist injection. Any suggestions on what is causing this CEL and what i can do to fix it. I've reset the code about 4 times now. Keeps coming back

thanks

that code does not hurt anything. the rear 02 is calibrated to the stock cat. not a high flow.

hence why you get the code.

I was running fine for three months, no codes ever, why all the sudden now?? Any ideas

some cars are instant on it, some take time. clear it, and go about your way

yea my subaru throws that code its just the sensor, clear it and move on

I get that sometimes with my vibrant dp.

Thats what I do too.

I have had the ZZP hi flow car for over a year now with no code, the cat could be shot.

The computer is tell you the CAT isn't doing it's job. The 2 O2 sensors produce a SINE wave and if the two sensors match that means the CAT isn't doing it's job any more and the code is produced.

You won't pass emissions with that code, no matter how many times you clear it, because the OBDII tests will never complete.

i have actually been throwing that code randomly in my subaru it would come on and go away its come on so many times i dont even bother with it any more, but i just got the car inspected and it did pass emission, granted the light wasnt on but that wont change what its like in the cat.. idk maybe i just got lucky.

everyone, thanks for the feedback. Looks like I'm stuck with it for now. Seems to be running OK.

yea it should run okay your are probably going to see a decrease in gas mileage though, thats one thing i forgot to tell you.

Dtc P0420.catalyst System Low Efficiency:spam:

Fortunately I haven't seen a decrease in gas mileage

I have cleared the stupid code 3 times but keeps coming back, the car runs fine, just get used to the CEL.

Conditions To Running The Dtc;an Engine Misfire,high Engine Oil Or Coolant Consumption,retarded Spark Timing,a Weak Or Poor Spark,a Lean Fuel Mixture,a Rich Fuel Mixture,a Damaged Oxygen Sensor Or Wiring Harness,the Catalyst Test May Abort If The Vehicle Falls Out Side The Conditions For Running The Dtc,a Catalyst May Be Temporari Degraded If A Fuel With High Sulfur Content Has Been Used.:confused: ?

your lucky im filling up my subbie about every three days, its getting about 230 miles to the tank, i think it should be getting almost 280-300...

i got this code instantly with my ZZP DP.

Same error, here's something to try
 

I'm getting this same P0420 dtc using Hahn Racecraft header and hi-flo down tube.

You can use your VCM Editor, like HP Tuner, to change the error limit or disable it. By default it's set to 0 - MIL on first error. Hope this helps.