Volvo: check engine light for Volvo 960, 1996 volvo 960, volvo 960

Question
Hi. I recently purchased a used 1996 Volvo 960. The check engine light has come on. Then the gear shift got locked. I was able to unlock it but cannot get the check engine light to come off. I tightened up the gas cap, so hopefully that's it.  What do you think is the problem? I've also had some problems with the car not wanting to start?  Could there be a electrical glitch?
where in the car can I located the error code box, before taking it in, can i check other things? please help....

Answer
Mark,
Without a scanner that will read the codes in your car, taking it to someone that has one is the only way to read the codes. There is not a way to read them manually. If the car will not start maybe the answer is in the fault codes.
On the shift lock the micro switch for the lock out solenoid is the weakest link in the system. That parts gets replaced very often.