There is a test for the air temp sensor. It is buried somewhere in the manual CD.
I could e-mail you the whole section in the manual, and you would have to search it. The file is about 5 megs (.pdf - 173 pages). Send me a PM with your e-mail. I am too lazy to look for it.

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1999 Porsche 996 Carrera Convertible
1994 420E - SOLD
1986 300E - SOLD, what a car
609 Certified