Potential relevant history: A few months ago I got P2097 Post catalyst fuel trim system too rich bank 1 997 turbo. I reset the code to see if it was a fluke, the code never came back.

Since I don't drive the car very much, the ready codes for smog weren't ready. I also remembered the CA supposedly now checks ECU tunes, so I flashed back to factory tune this morning, the only aftermarket parts I have now are headers and high-flo cats.

I drove the car around this morning and got most of the systems flipped to the ready state expect for Secondary Air System. I waited several hours and then followed the procedure to get Secondary Air System ready, mainly, idled for 10 min, and then checked the codes again. Secondary Air System still wasn't ready, BUT, I did see two new codes (NO CEL). P0420 & P0430. These codes weren't there before I did my 10 min idle today.

I looked those codes up, and they say my cats are bad. I have a hard time believing they would all of the sudden be bad. I tried looking up what the O2's are saying, and I only see downstream O2's in durametric, not upstream (should I see those?)

And when I looked at the voltage, this is what I see (is that saying -50 Volts?), that can't be right, but maybe I'm reading it wrong? And where are the upstream ones in the durametric?

My plan is to replace the pre and post 02's (if I'm doing the work, I'm going to replace them all), look for any exhaust leaks, clear the codes, and see what happens. Could the P0420 & P0430 be related to putting back on the factory tune, seems like the only plausible explanation?

Anybody else have any thoughts?

 

If I remember correctly, the SAI's purpose is to inject more air into the exhaust on start up so the cat's can heat up and process the exhaust air to keep emissions lower.

The codes may be related to that, and fixing the SAI may solve both problems (if you have not fixed it yet). In PA you can have 1 ready indicator fail and still pass inspection.

Ed

 

If your previous tune coded out the rear O2 sensors, that would explain it. It seems unlikely they both failed simultaneously. You’ve also got the visual component to contend with. I’ve no idea how problematic the headers will be for visual. But they often scrutinize your cats. You could also try O2 extenders, but those could be flagged on visual too. Four O2’s is a chunk of change. The money may be better spent on a used stock exhaust to swap in for smog.

 

997.1? Read the voltage on the post-cat 02 sensors (narrowband). They should read between 0.0 and 1.0 volts. Based on my research and experience, a normal reading before they trigger a cell is between 0.5 and 0.8 volts.

Your pre-cat sensors (wideband) should read between 0.0 and 5.0 volts. I think it’s about 0.5 to 4.5 volts, to be honest.

Values in your screenshot seem funky. Show me front O2 sensor values, if they’re funky as well, we can hopefully un-funk them together inspector gadget style.

 

I had aftermarket cats that failed with those codes… out of the blue (and with <7k mi on the car). The only solution for me to be able set codes and pass California smog was to replace with a used OEM exhaust/catalytic converter.

 

Following back up. I opted to first try and replace all 4 O2's. Reset the codes, replaced my Werks1 intake with stock intake (so I wouldn't fail visual), and then took the car on an 800 mile cruise around Northern California with some friends last weekend. No more error codes and the car passed smog fine this morning!

What's strange, I still don't see my pre cat O2's show up in the Durametric engine "actual values" list, only post cats, not sure why, but now that things are looking healthy again, who cares.


out with the old!



Car drove flawlessly



And as a bonus. I'm getting the best gas mileage I've even gotten on the freeway, and the acceleration is smoother.

 

Many older tunes 'code out' the pre cat sensors . . .

 

Goodness gracious I hope they don’t haha. They’re the important, wideband sensors. 0V-5V

Its the secondary, so post-cat o2 sensors that get disabled. Usually narrowband. 0V-1V (ECU wants to see 0.5-0.8V roughly, which confirms catalyst operation is within the spec)

 

My car popped a P0420 code out of the blue today.


Other than an aftermarket Speedtech exhaust with 200 cell cats, mechanically the car is bone stock. The exhaust is only 4 years old and has maybe 8K miles on it. No way the cats should have gone bad right?

Like OP, Durametric gives me no upstream O2 values to read, only downstream, and I see numbers in the -50 range.

It flutters around slightly but for the most part just hums along right here in both banks.

Are we sure about "They should read between 0.0 and 1.0 volts" ?

 

Reset. Try again, drive real easy until all clear. Report back.

edit: don’t drive aggressively. Reset and just drive normal. Not too easy or aggressive.

I had the same thing.

edit2: something is off that you can’t read pre-cat values. Call someone specialized to inspect your tune or log anything O2 related and attach to here for us enthusiasts to review.

something is off.

 

my plan was to reset and see what happens.

as for the O2 readings, my car is not tuned. like op it’s not that i’m not getting any values for pre-cat readings, it’s that durametric doesn’t even display an entry for them. they are not available to select.

 

yes, durametric will show both upstream and downstream if you select the correct boxes, I've used that function many times. Sorry, I don't remember which boxes to check, but I think they were easy to find.
upstream should vary, downstream should not +/- 0.2V

I just saw that you got it sorted
and the note about tunes deleting pre cat values, that makes sense.