My car has finally given one of the dreaded, incredibly uninformative "check engine light"s

I was told there was multiple ways to diagnose this light ranging from complete diagnostic systems to simple home-brewed impulse counters.

I was also told that you could use a multimeter.
Now i have a couple multimeters laying around, but do they have to be able to read something special to be able to be used for diagnostics?

Also, I'm somewhat of a car junkie, and I take every oppurtunity to get my hands dirty, but when it comes to diagnostics I'm utterly useless.

I know there is some sort of connector on the driver's side fender, a circle shaped 9-pin connecter, but is this the diagnostic port?

Assuming it is, how would I go about using the multimeter (assuming i can) to read the codes?


I know this is alot of questions, but any help would be appreciated.

Thanks in advance,
-E

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I love my cars to death but my wallet sure doesn't.