P0420 P0430 codes and car won't start

[Mouse330]

While cranking with a scan tool or code reader that’s shows data see if there’s a cranking rpm

[pyroguy]

Originally Posted by Mouse330

P0420 and p0430 are catalytic converters efficiency codes. Does not mean the cars are clogged! Not going to produce a no start issue

I pulled the cats and they were not clogged. I'm far from stock these days and I believe the cat code was from headers with high flow cats.

[imponte]

Hi, i have the same problem. But only cold weather, cold start cause this issue, car is just starting but after 1 second the engine stoppng.. Second try no issue, it has a perfect start..
The car spec: Slp long tube headers, small handmade mufflers instead of the cats, and slp catback xpipe..
I know this codes dues to O2 sensors.

Here my question. My car have 2 O2 sensor, one before cat, one after cat. Can i just turn of the after one w/ tune? Is this important for the air/fuel ratio, or just for the cat is there or not? I've heard that in some vehicles, two sensors are adjusting the air-fuel ratio

[pyroguy]

Sorry for no final update on the issue. Believe it or not, without throwing a code, my cam position sensor went out on me. Nothing to do with the cats or O2 sensors, and my tuner said this was the first time he'd seen a cam position sensor go out without throwing a code. Overall he has seen very few cam position sensors go out, but this was a first without throwing a code for him. He tried to see if the car had fuel, it did, then tested for spark, it didn't, so he chased the wiring around to make sure nothing chafed or burned/melted, which it hadn't, so he replaced the cam position sensor and the car fired right up.

[imponte]

Originally Posted by pyroguy

Sorry for no final update on the issue. Believe it or not, without throwing a code, my cam position sensor went out on me. Nothing to do with the cats or O2 sensors, and my tuner said this was the first time he'd seen a cam position sensor go out without throwing a code. Overall he has seen very few cam position sensors go out, but this was a first without throwing a code for him. He tried to see if the car had fuel, it did, then tested for spark, it didn't, so he chased the wiring around to make sure nothing chafed or burned/melted, which it hadn't, so he replaced the cam position sensor and the car fired right up.

Good for you But my issue is totally different. I have catless pipe.

Here my question. My car have 2 O2 sensor, one before cat, one after cat. Can i just turn of the after one w/ tune? Is this important for the air/fuel ratio, or just for the cat is there or not? I've heard that in some vehicles, two sensors are adjusting the air-fuel ratio

[imponte]

Any suggestions?

[InFiD3ViL]

Imponte, yes, you can turn off the reporting on the rear O2 sensors via a tune safely. They are only used to measure catalyst efficiency on these cars, not for altering AF ratio.

Pyroguy, I don't find that all that surprising anymore. I have had 2 upstream O2 sensors fail on me on my car and it never threw a code. The second time one failed the sensor was completely dead, zero voltage. You would think major sensor failure would trigger a CEL, but I gave up on relying on the CEL. Now, any strange behavior in the way it runs and I scan it immediately and check trims and O2 behavior/speed.

[imponte]

Originally Posted by InFiD3ViL

Imponte, yes, you can turn off the reporting on the rear O2 sensors via a tune safely. They are only used to measure catalyst efficiency on these cars, not for altering AF ratio.

Pyroguy, I don't find that all that surprising anymore. I have had 2 upstream O2 sensors fail on me on my car and it never threw a code. The second time one failed the sensor was completely dead, zero voltage. You would think major sensor failure would trigger a CEL, but I gave up on relying on the CEL. Now, any strange behavior in the way it runs and I scan it immediately and check trims and O2 behavior/speed.

That's what I'm looking for