cardoc:
Any experience with the 2005+ and perhaps other later models?
There doesn't appear to be a specifically-identified "STFT" and "LTFT". (See attached list from 07 FSM).
I believe the relevant PIDs are "AF Correction #1" and "AF Learning #1" respectively but would appreciate your comment, especially as this might be useful for others using this thread as a P0420 troubleshooting guide with a later model that might not read out the STFT and LTFT.
Also note that there's also "AF Correction #3" and AF Learning #3" which, like the other two, will show up with those descriptions in scanner readouts but are not otherwise identified as to their significance.
(Incidentally, all of these PIDs show up when scanning my 07 engine PIDs with Romraider Logger, however "Intake Manifold Absolute Pressure" is identified as "Boost". It took me a while to make this connection . . .)
For some reason, your attachment isn't opening. I'll look into that later.
RomRaider is a tricky software package. The definitions for the ECMs are generalized for use with multiple types of ECMs and TCMs.
The Denso ECM begins a learning curve for fuel trim every time its started. It does this due to changes in temperature, pressure, etc.. Once it learns the new fuel trim data necessary, it stores it and uses that value for all closed loop operation.
The AF values are calculated in Lamda, EQRatio 1/1, 2/1, 3/1 depending on H4, H6, NZEV or PZEV vehicles, but you can change the value in RomRaider to show AF at stoichiometric if it makes reading the data easier.
The AF correction and AF learning are the values utilized by the ECM to calculate closed loop trims. The LTFT and STFT can be calculated based on the Learning and Correction respectively. You just have to watch it while you log and do the math. Or graph it and watch the waveform. Once the computer realizes there has been a change in data input, it goes back to the correction and learning to compensate. Its when there is an issue with performance and the computer is making a lot of correction in its learning curve that the MIL comes on. It sees an issue with the LTFT learning, or that input data is out of range and sets the code for the system it believes is the issue.
Now, to effectively diagnose the issue with a P0420 using aftermarket software and determine where the problem lies, and we will use RomRaider since it is widely used by Subaru owners for various reasons, log the data from the rear O2 sensor. In RomRaider, click the Rear O2 Sensor and use either Amps or Volts. When graphing this sensor, the activity of the sensor is the same as any other scan tool and the value will remain steady rich or lean indicating a fuel or ignition issue, or it will fluctuate rich/lean based on the AF Learning value
You don't necessarily need the AF values to determine if a CAT is bad. All you need to remember is the O2 sensor reports the Oxygen content of the exhaust exiting the CAT. Anytime you see a wave instead of a steady value, the CAT is bad. Otherwise, with a 420 code, you are looking to see if the O2 is rich or lean, then start with locating the issue with engine performance following with sensor outputs.
As far as the RomRaider component title in the log lists, as long as you know what you are recording, all is good. As long as you understand what values are necessary for proper performance.
My VDC actually reports Lamda values, but I can alter the RomRaider to show Stoich. I also have different scan tools that show different values. The EVO will show Stoich or Lambda depending on which value I choose to look at, either AF or EQ.
I will record a video of my car and post it if I get time today. I will use both the EVO and RomRaider. You'll just have to remember I am running E85 and have 2 6.2L cats installed so the O2 sensor values will be scewed. I just get hot air out the tailpipe.
