355 CEI Code Po422 Again

Isn’t it the function of the rear O2 sensors to determine if the cat is faulty and not the engine itself? Why should there be a code for failed O2 if the engine is ok?

How old are your cats? Are they OEM? Maybe you need to inspect them for damage and have a “sniff” test done?

 

Do you have aftermarket cats?

 

A bad MAF would also likely throw a CEL and would cause drivability issues such as poor throttle response, stalling at idle, hard starting..... Down stream O2 sensors are cheap. If they are 10 years old I'd replace them. Plus, if you get a P0422 and you reset the ECU, it takes time for the cat monitor to come back on line so it's typical you wouldn't see again immediately.

Or, replace the MAF and report back.

 

I'm just trying to understand the logic (yours and the car's)

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If the rear sensor is doing the job of detecting cat aging (a), then why would the ECU fail the O2 sensor if it is doing the correct job? Can it not differentiate between a and b?

Seems like a reasonable lifespan for modern mass-produced components, depending on mileage, but if the cats are original, then they are probably long overdue for an inspection.

 

If o2-2 is reporting information (bad or good) I wouldn't expect it to present an failed o2. If o2-2 is closely mirroring 02-1 it's likely the cat is end of life. Based on your provided info I wouldn't expect it to be MAF other than that's an "easy button" to try.. but realistically they are getting hard to find so maybe not such an easy button. A bad o2 would present as something else.

Is this the same code on both sides? Or only 1? On the majority of cars (5.2) it's a single MAF so you'll see the problem on both sides if it's MAF. If you're only getting the error on 1 bank look elsewhere.

Also the opportunities for exhaust leaks are plentiful which will mess with o2 readings. The exhaust paths are very short and it's quite a juggle to get everything to align, tight, and not leak. The o2-2 is literally about 2 inches away from the muffler connection that has a connector that is almost impossible to get leak free. The upstream donut joints on the bypass and cat junctions are also a challenge. I've realigned mine a few times, it still leaks some..

 

I did not write the firmware for this car so I am just guessing.

The ECU knows when it adjusts the mixture on bank 1, and it can monitor the Upstream O2 sensor to see the waveform to be changing to rich condition. It has a parameter for xx millisecond from adjustment to O2 signal showing the rich condition. If the parameter takes longer, then it throws up a CEL for that sensor being aged. This test can take place during self test of the monitor, or during actual driving conditions. If it decides that the Upstream sensor is aged, it will rely on the downstream sensor signals to do some mixture adjustment. Given the fact that the Downstream signal will always be slower than the upstream signal, I don't know how accurate the mixture adjustment will be. Maybe in would go into a default mixture such that it does not burn up the cat.

The ECU has a parameter for what the normally changing Upstream sensor signal looks like, and a parameter for a normal Downstream sensor signal should look like through a functioning catalyst, If the down stream signal is too fast to be more like the square wave of the upstream signal indicating that the catalyst is losing functionality, the ECU throws up a CEL for cat inefficiency.

Sophisticated software like this is written in structured code where every process is independent and communicates with each other via Programming Interfaces. Given that this would be the first instance for OBD2 management from Ferrari, it is easy to imagine that some corner cases are not yet worked out. For example, if the Downstream o2 sensor is bad, why is its signal being used to generate Cat Inefficiency error? I can say that the O2 sensor management code on the 360 (next model from 355) is much more sophisticated than that on the 355. They did learn something.

 

For info, Dave "Rocks" Lelonek had this code and it was his cats breaking up.

 

Good luck with the new MAF.

But FYI,

A 30 year old roof may not leak, but that doesn't mean it doesn't need replacing. Same with an O2 sensor. Failed (P0130) and giving bad info aren't necessarily the same thing. I've personally fix numerous cat efficiency codes by replacing the rear O2 sensor on vehicles.

Why P0422 and and P0423? Because problem is isolated to bank 1. Could be the rear O2 sensor. Could be an exhaust leak. Could be a bad cat. But this kind of speaks against the MAF.

When you erase P0422 you also reset the OBD II monitors. If you don't follow a specific drive cycle it can take severs drives and up to 100 miles (sometime more) before the monitors come back on line. Until they do they can't report problems (I.e. set a code and turn on the CEL)