P2196 and P2198 codes after fill up (intermittent)

Okay, got a REALLY interesting issue. Which seems to be getting progressively more frequent as time passes on.

I fill up my vehicle with fuel and prior to filling up it runs perfectly fine. No issues whatsoever and fuel control is correct. The engine could be hot or cold, so this is not temperature related. After filling up, upon the start up, the RPM begins to drop down to the idle range and then has a hard time regulating. I inspect my air fuel ratio gauge and see an air fuel ratio of less then 9.0 AFR.

Upon inspection of PID data on my scanner I can see that STFT fuel control is going haywire at -20% and greater for both bank 1 and 2 simultaneously.

I never obtained codes regarding this occurrence until tonight after filling up I found a pending P2196 and P2198. The codes basically state the air fuel ratio sensor for bank 1 and 2 are stuck biased rich.

As previously mentioned, fuel control is NEVER an issue prior to fill ups. This condition has only recently started occurring over the last 3 or 4 months and has progressively become more frequent after fill ups.

A little background about the truck

2012 Supercharged
Automatic
Air Injection present
96,000 miles
Truck otherwise runs great

A little insight and or ideas would be extremely helpful, but I know this issue is not directly being affected by failing oxygen sensors.

The only thing I can think of which could be causing this is a stuck open EVAP purge valve, or a AIR injection system which is injecting air while it is not supposed to. However, that still begs the question. WHY AFTER FILL UP ONLY?

 

I'm thinking stuck open purge valve too, although I'd think you'd have evap codes if that were the problem. I work on Fords mostly but I think it works the same for other brands too. The purge valve is normally closed so an easy way to see if it isn't closing is to unplug the connector and remove the hose from the tank side of the purge valve and see if you feel any vacuum at the valve while the engine is running.

I had that same problem when I did an ls1 swap in a car I had. I didn't understand the system at the time and removed everything I thought I didn't need, which included the purge valve, which was fine, except that I ran the vent hose from the gas tank directly into the intake. Every time I filled up, it had a hard time starting and idling since the fuel vapors were getting pushed up the line into the intake. Figured out what was going on and no more problem.

 

Are you overfilling the tank? Pull the canister down and see if it's full of liquid fuel. Alot of cars are programmed to purge on cold startup. If the canister is saturated it could cause this

 

I have never done that for the very reason that I knew that if you go past the gas tanks auto shut off function you will start flooding the canister. The canister when I inspected the lines and it when I was having the issue were clean and clear.

Just to update this thread it turns out that I had some junk clogged up in the evap system. I ran low pressure smoke through the system to pressurize it and check for leaks. By relieving smoke out through the fuel cap area a few times while it was being smoked, whatever was lodged in the evap breather lines ended up getting cleared out because the issue ceased to exist ever again after doing that.

This case has been closed. Lucky for me.

 

Glad you got some closure, evap systems in general are finicky as hell

 

Very much so. It's a poor design and I've been saying it for years.