check engine light

[chan]

hi all
i recently purchased a 96 mustang coupe
i just had a tune up done (basic) plugs, filter, fuel oil change etc
ever so often i keep getting the check engine light on the panel
i reset the system by dis-con the ground term. the light goes away but pops back up every few days.
the manual says it's an emission problem but i just passed the NY state emission test plus i just had a tune up...
can you shed some light as to what may be wrong??
I've been told the sensors need to be checked!
Any other sugggestions??
thanks
chan

[PNYXPS66]

Chan:

First, just clearing the codes won't help you with your problem. Additionally, if you are clearing them by removing the ground wire from the battery, you could possibly damage other components including erasing memory in your ECM that makes the engine run. I don't suggest doing that.

If the ECM registers a problem code from one of the many sensors, the light comes on. The first thing to do is to get the actual code number from the ECM memory to find out exactly what is wrong. You can take the car to any shop and they should be able to pull the codes and tell you what is wrong. You are correct that it's probably an emissions issue. The most likely problem is a failing Oxygen sensor. You can have a failing O2 sensor and still pass emmissions tests. Since the car is a 96 I imagine it has over 50K miles on it. You should replace the O2 sensor every 50-60K miles like a fuel filter. You can get them at any parts store like Napa or Auto Zone. Prices can run about 20-50 dollars depending on the vehicle. The sensor is located on the exhaust manifold or on the tail pipe just before or after the catalytic converter. You may actually have more than one; some vehicles with v-6's and v-8's have one on each exhaust manifold, and may have one before AND after the catalytic converter. I recommend replacing all of them at the same time lest you replace on and it doesn't solve your problem. Or, you replace one then a week later you have to replace another because it was weak also.

Hope this helps and good luck.