nissan sentra - check engine light

[heaton]

We have a 2000 Nissan Sentra - the check engine light has been on for over one year and will only turn off if the battery is disconnected (for about 20 miles). We have had it into several dealers/shops, and get a different answer every time (o2 sensor, air filter, fuel injectors) - ranging from $500 to $2000. How the heck do we really know what it is and how can we just turn it off, the car seems to run fine.

[ogpala]

Did the dealer give you any error code? I suspect it is the Mass Air Flow Sensor (MAF) located on the air intake manifold after the air filter. I have the same problem with my 2000 Corolla. You can clean it yourself or ask the dealer to do it. Give it a try rather than pay a handsome fee for them to second guess.

[heaton]

The dealer did not give an error code - one dealer said it was the O2 sensor, another said an air filter, and yet another said the catalytic converter. I'll get the error code and have the air intake manifold cleaned. Thanks for your help!

[ogpala]

Make sure you have a clean new air filter and clean the MAF sensor also. Reset the light by pulling out the EFI fuse (should be in the fuse box near the battery) for 10 sec instead of disconnecting the battery terminal. That will reset the check engine light.

Test drive your car on the Highway and if the engine light does not come back after the cleaning and test drive, then you have the solution. If the engine light comes back after the test drive, you need a mechanic to fix your problem. Make sure you get the error code from the mechanic to pin-point the actual problem. My Corolla needed a new MAF sensor ($250+), cleaning would not work.

Please note that the proper procedure to reset the light is with a scanner (computer). The mechanic or dealer will charge you about $50 + taxes.

Take your car to AutoZone, they will check your code for free.

[mospeed1]

is your car still under warrenty?

[Creagach]

usually speaking cleaning a maf isn't a good idea there is only two small wires in there that look like filaments for a light bulb they are pretty delicate and if your air filter is attached there shouldn't be anything dirty in it, it's past the pcv and crankcase catch can so what would get it dirty?

[mmcleo11]

Creagach, usually the MAF is dirty from small backfires, which leaves carbon deposits on the wires. This will affect the resistance of the wires, giving an error and making the car run slighty rich...
Heaton: Is the cars exhaust a bit more smokier than normal??