I have a 2009 Prius and get the p2196 almost every time I drive the car. The rich condition only happens occasionally during off throttle deceleration, typically after a period of having been heavier on the throttle, and it only happens briefly. I have watched the real time air/fuel and seen it spike for a brief second to trigger the code. After the code appears I can clear it right away, and it stays away until it gets similarly triggered again. Thanks for any help.
I got a Prius with this problem but the other error code related to this... P0138. I've read threads about replacing upstream sensor solving the problem but I don't know the tune up history of this 2004 Prius. So I plan to do the tune up/engine care first and then work on the error code next. Of course I haven't seen the error code in a while, so I might lose my motivation...
What region in the US are you? As in what's temperature and humidity / weather where you're having those symptoms? I got a Prius in PNW with this problem but its the other error code related to this: P0138. I've read threads about replacing upstream sensor solving the problem but I don't know the tune up history of this 2004 Prius. So I plan to do the tune up/engine care first and then work on the error code next. Of course I haven't seen the error code in a while, so I might lose my motivation... How about you? What's your engine care history?
I can verify that both upstream and downstream sensors have been replaced with OEM new ones. It also has a new MAF sensor. It is also worth mentioning that I drive the car hundreds of miles a day on average. It used to burn a ton of oil, but a b-12 piston soak got it down to burning slightly less than a half a quart between oil changes.
If you want to find out if your ECU is correct - pull your spark plugs and inspect the tips. If you don't know what a lean vs rich burn spark plug looks like - there's plenty of examples on an internet search. What are the chances that you have a leaky injector or two. Spark plug should tell you that too. Hopefully you've got a clean air filter and checked your air intake pathways are clear. Good Luck....
