Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
hi I am not to experienced with A/f ratio sensors but since that is post cat code I would address the po420 first the moderators are good with A/f ratio sensors I have quite a bit of studying to do to understand those they are different from traditional o2 sensors
ScannerDanner has numerous tests for either A/F or O2. I suggest you do them to ensure your sensors are good. In a nutshell, they involve introducing propane to the intake to ensure the sensors sense rich. In a similar fashion, you introduce a vacuum leak to the intake to ensure the sensors sense lean. You would monitor the sensors as someone else drives as well.
In addition, please send freeze frame data. If lean codes at idle (low rpm), could be vacuum leak. If at higher RPMs, maybe it is caused by lack of fuel or MAF. More information and more tests will allow you to narrow it down.
I agree. Fuel trims would be a good place to start. Even though a/f sensors are not the same as O2 sensors, interpreting the fuel trims applies to both the same.
Tyler posted a great sticky thread on testing a/f sensors.
Hey what's up freedom auto? Yeah I would check fuel trims like the guys are mentioning as well. Make sure their Is no exhaust leak upstream of the cat as that would cause confusion to the 02 sensor and also flag the p0420. Make sure that 02 that was put in is OEM or at least denzo. 02 sensor should switch from rich to lean if I'm not mistaking in 100ms. Graph the 02 with short term fuel trim only and see how it switches. I would go to global 0b2 and see them there as the manufacturers give different voltage numbers and confuses us. Good luck let us know what u find
The P2096 makes me suspect an exhaust leak that's influencing the catalyst and downstream O2 performance. It doesn't take much - even a sensor gasket leaking is sometimes enough. Many OE's are recommending to pressurize the exhaust system to around 5 PSI and spraying soapy water to detect pinholes and leaks. I made up my own tester from an exhaust cone and a pressure regulator.
If that comes up negative, consider if the downstream O2 itself is skewed. Make sure that it agrees with the upstream A/F sensor as you introduce rich and lean changes. Does the downstream sensor switch rich and lean while cruising at steady throttle?
What brand of cat did you install? Aftermarket is a crap shoot. :silly:
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