I have a 2006 Sonata with about 40,000 miles on it. Recently the check engine light came on, and checking the codes revealed a P2187, System Too Lean At Idle Speed.There were no other codes. I cleaned the MAF sensor. Checked for vacuum leaks as best I could and found none. I also checked the air filter and it is clean. I cleared the code, but the check engine light came back on within a day, revealing the same trouble code.

Does anyone have any suggestions on what else to try? I'm thinking it is probably an oxygen sensor, but which one? I do not have access to an OBDII tool that can do real-time analysis.

 

Warranty = 10y/100k miles (5y/60k miles if used)
Your car = 3y/40k miles

Why don't you just take it to the dealer to have it fixed under warranty for free?

 

Which engine?

 

The engine is the I4. (Sorry about forgetting some obvious information.) I had thought it could be related to ethanol in the gas, in reference to which gas is used. Currently I use 87 octane, and have always used it.

Why not take it to the dealer? In reading over the complex warranty, it was hard to tell under just what area an oxygen sensor would fall (fuel, emissions, engine)? I came to the conclusion that an oxygen sensor was covered under a shorter period of warranty that had already passed, hence my desire to diagnose and repair the problem myself.

 

I don't know what you mean by "shorter period of warranty". If you live in the US or Canada, you get 5 years or 60,000 miles if you are NOT the first owner, or 10 years/ 100,000 miles if you are the original owner. Oxygen Sensor clearly falls under the heading of "Powertrain". Take it to the dealer, and just ask them if it's under warranty.


Looks like you're right, it's probably the primary oxygen sensor (the one before the catilytic converter). Be careful cleaning that MAF sensor, they usually don't need cleaning, and it's easy to destroy the element inside.

 

Unless you accidental filled up at an E85 pump, I don't think ethanol is the problem. I do not think the O2 sensor is to blame either. The O2 sensor is reading a lean state at idle, which means unmeter air is getting into the engine. I've heard of this happening with cars with a vacuum leak, where the intake manifold was removed and replaced without replacing the gasket or from a leaking flex pipe on the exhaust. I suspect a faulty EGR or purge valve that is stuck open which would tend to show up as a problem only when the engine is idling. I agree that this is a dealer issue where a dynamic monitor of the emmisions system can be used. It should be a warranty repair, but you can always ask first to make sure.

 

I agree with Ken, ethanol is not the problem. Trust me, your car is still under warranty. Let the dealer diagnoseand fix it for free.

 

Okay. I will schedule an appointment with the dealer and take it in. I'll be sure to post back what the problem was. Thanks for the help/support!

 

The dealer replaced the intake manifold gasket to resolve the problem.

 

Very good. Thanks for letting us know what happened.

Ken