P0420 freeze frame data

[rc_cola_j]

Hi all,

 

After changing my O2 sensors last week, I'm now randomly throwing a P0420 code. Below is the FF data. Can anyone interpret this? I've read that if the fuel trim is low it could be a fuel injector or fuel pressure regulator problem....if it's too high I could have a vacuum leak. But I don't know what I'm really looking at here....thoughts?

 

 

 

 

 

 

 

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[bushnut]

So the stft and the ltft are: Short Term Fuel Trim and Long Term Fuel Trim respectively and B1 and B2 are bank 1 and 2 meaning left and right side of the engine. The fuel trim numbers are the air fuel ratio that the ECU is making. + numbers mean more fuel to air and - numbers mean less fuel to air.. Ideally the air /fuel mix should be something like 14.7 to 1. on the scan tool closer to zero is best. Short term means every few seconds. Long term is over minutes or hours. that number shouldn't change very often though the STFT will change every second or so. If you have High + numbers like 20% or more could indicate a vacuum leak as more air is in the system for the ECU to mix in enough gas. High - numbers could mean a fuel leak. ( I had this twice with leaking injectors that killed my Cat)

 

Cal % load...is how hard the engine is working in your case 54%

fuel sys...CL means closed loop..

ETC is engine temperature in degree Celsius 84 is good that is operating temp.

MAP kpa is air pressure into the engine in KILO Pascals.

RPM is well RPM

 

all of this looks pretty normal to me....

I'd be checking electrical issues related to missfire

hope this helps

 

[rc_cola_j]

So the stft and the ltft are: Short Term Fuel Trim and Long Term Fuel Trim respectively and B1 and B2 are bank 1 and 2 meaning left and right side of the engine. The fuel trim numbers are the air fuel ratio that the ECU is making. + numbers mean more fuel to air and - numbers mean less fuel to air.. Ideally the air /fuel mix should be something like 14.7 to 1. on the scan tool closer to zero is best. Short term means every few seconds. Long term is over minutes or hours. that number shouldn't change very often though the STFT will change every second or so. If you have High + numbers like 20% or more could indicate a vacuum leak as more air is in the system for the ECU to mix in enough gas. High - numbers could mean a fuel leak. ( I had this twice with leaking injectors that killed my Cat)

 

Cal % load...is how hard the engine is working in your case 54%

fuel sys...CL means closed loop..

ETC is engine temperature in degree Celsius 84 is good that is operating temp.

MAP kpa is air pressure into the engine in KILO Pascals.

RPM is well RPM

 

all of this looks pretty normal to me....

I'd be checking electrical issues related to missfire

hope this helps

 

Dude, thanks.

 

Misfire? Bad Cat converters?

 

 

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[Bunchie]

They say average life span is 100k miles...so what THEY are also saying is I should have changed them YEARS ago-haha, didn't get that memo! Add them to the list of req'ds....sigh.

[bushnut]

P420 is catalist below threshold. could be the catalytic converter has failed the question is why. read this..... ttps://www.obd-codes.com/p0420

Edited June 2, 2017 by bushnut

[adamzan]

Yes, figure out why. My parents r50 went well over 300k km on the original converters, never an issue... Yours also could have been bad for a while, but the old sensor was @!*% and wasn't picking it up. Great if you want to run headers, lol. Misfires, running too rich (due to misfires or bad primary o2, or other sensors), and burning oil destroy converters. They are technically designed to last the life of the car, they don't just "go bad". They just get destroyed by other issues that most people don't notice right away.

 

Unfortunately once that code comes up there isn't much you can do short of replacing them. Don't fall for any of that cleaning your cat BS. You want to be very careful with the manifold converters. On my Xterra they came apart and scored the cylinder wall of my engine. Which = massive oil consumption.

[rc_cola_j]

So I got up a little early today, warmed up the car and ran the engine at 2500-3000rpm for a few minutes. Then watched the O2 sensor values in the scan tool.

 

For the most part, they all look normal. However, Sensor 1 Bank 1 periodically spikes up anywhere from 1.8 to 2.3V....what could be causing this?

 

 

[bushnut]

what do the fuel trims tell you in relation to the O2 sensors. A high Negative value means the ECU is cutting fuel so you might have a leaking injector...that was my problem. A high + positive value means an un metered air leak. use some brake keen or something to spray around the intake manifold while the engine is running., you'll know right away if there is a vacuum leak.

[rc_cola_j]

what do the fuel trims tell you in relation to the O2 sensors. A high Negative value means the ECU is cutting fuel so you might have a leaking injector...that was my problem. A high + positive value means an un metered air leak. use some brake keen or something to spray around the intake manifold while the engine is running., you'll know right away if there is a vacuum leak.

I'm looking at short term trim values or long term?

 

 

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[bushnut]

long term. also does it burn oil? is there any exhaust leaks?

[rc_cola_j]

No oil burning.

 

There is one pinhole leak near the muffler....(after the downstream o2 sensors.

 

The EGR does stick open from time to time....would this be causing this issue?

 

I'll check the field trim in a few mins.

 

 

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[rc_cola_j]

Both the Bank1 and Bank 2 fuel trims read steady at -10.2% (at idle after a good drive)

[rc_cola_j]

if my cats are gone, how do I know for sure?