1996 Pontiac Grand Am Reversed Polarity

A scan tool will tell you if computer is cooked, but most likely there is a fuse or fuseable link/relay blown.

Remove and check each one, one at a time.

[quote:b77dac45b1="mmprince4000"]A scan tool will tell you if computer is cooked, but most likely there is a fuse or fuseable link/relay blown.

Remove and check each one, one at a time.[/quote:b77dac45b1]

I have checked every relay, they all are fine and I would have to tow my car to have access to a code reader. All fuses are fine. The local parts store says I would not be able to get a code unless the chk/engine light is on which it isn't. any other ideas, is it possible to diagnose the computer any other way?

96 and above are OBDII and diagnosis can only happen with a scanner.
A scanner will tell you any problems with PCM, but if you don't have access to one,

Check spark using plug grounded to valve cover bolt, if OK, then check fuel by spraying starting fluid into intake, if engine runs, then fuel issue, if not then spark.

[quote:5f44f900d7="mmprince4000"]96 and above are OBDII and diagnosis can only happen with a scanner.
A scanner will tell you any problems with PCM, but if you don't have access to one,

Check spark using plug grounded to valve cover bolt, if OK, then check fuel by spraying starting fluid into intake, if engine runs, then fuel issue, if not then spark.[/quote:5f44f900d7]

I have fuel pressure but no spark. I checked fuel pressure at the fuel rail. No luck with starting fluid into the intake. As I mentioned I don't want to pay for a computer if it is not the problem, I'm not sure what you mean by OBDII. I can get access to a scanner but will it tell me if the computer is fried?

A scanner will check PCM for any errors, so start with the scanner.

In 1996 ALL cars sold in U.S. switched to OBDII (on board diagnostics) from the older OBDI.

This is more sophisticated and is used for stronger emmission laws that went into effect.
They also mandated a common diagnostic port design.