Check engine light - 1999 Mercury Cougar

[Craig Rhoads]

My finacee's check engine light is on in her '99 cougar and the code indicates that "running lean, bank 2". Sounds like an O2 sensor to me but I was hoping someone could confirm and point me in the right direction as to which sensor it is. Thanks in advance for any help.

 

[Kevin Palmer]

The O2 is what sensed it and tripped the code. It could be a defective o2. But it could easily be something that triggered the O2 to trip the code.



If it is not the O2 itself then you have some sort of a vacuum leak I would think. Check out your hoses real well. While the engine is running spray some carb cleaner on the hoses and see if the RPM's change. If so, you have a bad vacuum hose.

 

[EddieS'04]

Also if you have an old squirt bottle, you can spray water on al the vaccum hoses. The engine will stumble if the leak is big enough.