Downstream O2 sensor codes 420 and 430
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Downstream O2 sensor codes 420 and 430
Hello. I have a C6 and a 2007 Suburban and thought I might find the best answer to a question about the Suburban here. It is used off road and doesn't need to pass New York State emissions. I don't have cats but have the rear O2 sensors in stock location. I get codes 420 and 430 and don't want to look at the CEL. I know the computer can be tuned to keep the CEL off but if a dealer worked on it or I ever decided to register it, the emissions readiness test won't show complete, correct? I have tried about six or seven O2 simulator extenders and none of them worked for more than a few weeks. I put my scanner on it and the voltage of the rear sensor is around .8 volts when driving but when I idle, it fluctuates enough to throw the codes. If I get an O2 sensor simulator extender and completely plug the orifice, will that work? All the simulators I have tried have different sized orifices and some even had little cats but none have been completely plugged to keep all exhaust from the O2 sensor. That would keep the voltage steady but not sure if it would be correct value. any ideas would be appreciated. Thanks.
Melting Slicks
Joined: Feb 2007
Posts: 3,297
Likes: 398
From: Raleigh Suburbs
No, you will not pass emissions with codes. Typically Vendors provide/sell simulators, with installation of headers or such, which trick the computer reading correctly. Might try contacting a Vendor here for advice, like Texas Speed and Performance (TSP).
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Thanks. I am experimenting with the O2 extenders and found by stuffing them with steel wool, I can control the dampening they provide to the exhaust getting to the rear sensor and it may work. I just wanted to confirm it can't be done thru tuning.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
Rear OS sensor are just montoring the cats only. They have nothing to do on how the engine runs, so yes, then can be turned off to they are not reporting errors in the tune.
So in either HP tuner, or EFI live, go into Engine DIAG, and uncheck SES enable boxes and change the last line to no error reported in the list below, then flash the tune back into the ECM with the error reporting changes.
P0036
P0054
P0056
P0060
P0137
P0138
P0140
P0141
P0157
P0158
P0160
P0161
P0420
P0430
P2270
P2271
P2272
P2273
Hence we are just turning off the rear bank 1 and 2 O2 sensors/not allowing the Ecm to send errors on what they are reporting.
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Dano, thanks. I thought they could be disabled so a CEL never illuminated but in states like CA and NY, wouldn't an emissions test show the ECM did not complete the emission test sequence and it would fail if i ever had to have it registered?
Melting Slicks
Joined: Feb 2007
Posts: 3,297
Likes: 398
From: Raleigh Suburbs
I don't believe so - there should/would be no errors reported to the PCM.
Race Director
Joined: Dec 2013
Posts: 12,502
Likes: 3,629
Burning Brakes
Joined: Jun 2015
Posts: 1,190
Likes: 311
From: Shelbyville Kentucky
You can also fool downstream O2's by installing an O2 spacer. It gets the O2 up out of the exhaust gasses and stops "cat below spec codes". Not needed if you just turn the off in a tune though.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
I am using the extenders right now and have experimented with different amounts of steel wool in them to let just the right amount exhaust get to the O2 sensor. It is working so far but think a tune would be better long term solution. I don't have to worry about a sniffer test in my state, just a computer scan for emissions inspection.
Melting Slicks
Joined: Feb 2007
Posts: 3,297
Likes: 398
From: Raleigh Suburbs
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
I bought HP Tuners and it was very easy to use. I unchecked the codes listed above and also disabled the Catalyst overtemp and Post O2 check. Hopefully that all works and the car will still scan properly. Thanks for everyone's help.
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Hello. I am also disabling the rear O2 sensors in my 2013 C6. I unchecked and did no report on the codes listed by Dano but also noticed a few others related to the second O2 sensors. They are P013a thru f and P014a,b. They are all about response time on the rear O2s. I unchecked and did no report on those too. Are those ones that others also disable when not running cats?
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
Thanks for everyone's responses. I had another thought on this. I did disable every DTC code related to the downstream O2 sensors along with catalyst overtemp protection in fuel control and catalyst and post O2 test in engine diagnostics. I have driven it a lot and it runs well with no codes.
Since I still have my downstream O2s installed (just my cats are gutted) could I have just left all the DTCs enabled and driven it to see what codes it threw and then disable just those codes? Would that make a difference in the readiness test when it gets inspected by the state?
Since I still have my downstream O2s installed (just my cats are gutted) could I have just left all the DTCs enabled and driven it to see what codes it threw and then disable just those codes? Would that make a difference in the readiness test when it gets inspected by the state?
Thread Starter
Racer
Joined: Jul 2013
Posts: 351
Likes: 24
From: New York
For an update on this I did the same modification to my Suburban and it just passed my state's yearly emission inspection so I can confirm you can tune out the rear O2 sensors and pass in states like NY and CA. My Corvette's inspection is due in the fall and I expect it will also pass just like the Suburban