I own a 99 ford escort zx2 and my check engine light has been on for quite sometime now and I have gotten it checked. It says switchessensor indicates lean. I have replaced the O2 sensor and I cleaned the MAF sensor yet I am still having this problem. If you know anything about this problem please let me know.

Without the actual code number I can only guess but the common lean causes are clogged fuel injectors, O2 Sensor failure or an intake leak. Now, there are two O2 sensors, one in front of and another behind the catalytic convertor. However, when these fail they usually have their own code. Check for cracked, loose or disconnected hoses around the intake manifold/throttle body and add a can of high quality (Lucas, STP, Techron) injector cleaner to your fuel and drive a couple hundred miles. Less frequent is if too much ethanol is present in the fuel. If you inadvertantly dispensed E85 into the tank to bring the ethanol content to around 40% or more, you'll get the same code. If this was the case simply drive it out and refill with regular unleaded. A one time occurence won't hurt anything. Let me know the exact code number and I'll see if anything else comes to mind. Good Luck!

my check engine light is on constantly as well. it threw a code for being to lean, right now the code number is slipping my mind. being in school for auto mechanics we worked on it for a whole day to find out why. figured out that it was the DPFE sensor(im pretty sure thats the intials, the differential pressure feedback EGR thing lol) which does nothing to harm or help the car, its like a 50 dollar part that we arent going to replace lol.

A piece of black electrical tape over the light will take care of it then! Glad you found it. Stuck EGR can cause lean as well. Bad sensor info can make light w/o real problem too!