Toyota Repair: K&N Systems & Check Engine light, mass air sensor, air fuel mixture

Question
2001 Toyota Tacoma, automatic. Installed K&N air intake system and "Check Engine" light is on. My application has both a crankcase sensor/element and mass air sensor on the air intake tube. So far I've tried; disconnected negative battery terminal at times as long as overnight. Made sure there are no air leaks around crankcase or mass air sensor fittings. With engine OFF pulled and then put back in the two ECU fuses. Any help is appreciated. Thanks.

Answer
Without actually knowing the trouble code I will give you the most common cause of the check engine light, part of it is caused by the K&N filter which contains some sort of oil, some of this oil along with dust particles can attach to the MAF platinum sensor wire, this wire measures the air flow in the intake tube and sends this information to the computer, the computer adjusts the air/fuel mixture, if the wire is coated with oil or dust it will send an erroneous signal to the computer which in most cases will drive the mixture lean and it will set an PO171 trouble code.  Try doing the following to solve this problem:
Remove the MAF from the intake, get some electronic parts cleaner from a computer store, using another cleaner won't work,spray the cleaner into the opening where the thin wires are until they look clean and shiny, either let it air dry or blow dry it with a can of compressed air available from electronic supply or camera stores, remove the EFI fuse or disconnect the battery for ten seconds, the engine light should go off, if this becomes a chronic problem consider installing the factory OEM filter.