Check Engine and Coolant Lights

I have had my check engine light go on over 4 times now. Each time I take it back to my mechanic and he says its something new and fixes the problem. The light will go off for about a day or two, one time it even lasted a week, but then it always comes back on. My mechanic is a friend and does not charge me that much for the fixes, so I know he is not ripping me off. The last time I got it back he said the check engine light might come back due to a 2 miss fires of the engine and of course it turned on again in a day. The Coolant light also turned on. For the first time. I asked him about it and he said he filled the coolant and that it must be the sensor inside the tank saying its empty when its really not. Is there anyway to shut off the check engine and check coolant lights. My car is not over eating it is running at the exact middle of the gauge.

The car is a 2000 4cl passat. With about 55,000 miles on it. Any help would be great. Thanks.

You problably have a faulty ECT. Its the coolant temp sensor and is located on the rear of the engine. ITs a 4pin connector and the old style sensor is black, the new one is green. The metal on the sensor tip corrodes.