Check engine light came on, borrowed a code reader, plugged it in, and didn't work. Checked another car, it worked. Whats wrong with my cars computer.

There may not be anything wrong with your cars pc, even if the obd-2 meter worked in one car doesn't mean it is for yours. They will only work on some makes and models. Look at the connector on the meter to see if it covers all points on your plug. If it does, it may not matter at all.If it were made for your car you would have some kind of reading, or your pc would be dead and so would the car. Run your car down to Auto-Zone and for free they will brings there's out to see why the check engine light came on. It usually comes on due to an emissions problem. They will give you the code and if its not a hard code which needs attention now, they can erase it. My 2004 Chevy Silverado's check engine light has been on for over a year now. I bought a meter and every now and then I will erase it. It will stay off long enough to pass smog, even though it shows an emissions problem. I would do the auto-zone thing if it were mine and you will know, its worth the drive.
Best of Luck,
Shastalaker7

That should be A OBD2 system you will need to check the DLC connector 16 pin to do so you will need a digital voltmeter to check the DLC if can git the book that came with the scanner it should have a appendix B in the back topic reference

SOUND LIKE EITHER YOU HAVE PCM FUSE BLOWN IF GETTING NO POWER. FROM 0BD 2 TERMINAL IT HAS POWER TO ITS TERMINAL WHERE YOU PLUG IN SCANNER.OR YOUR SCANNER HAS TO POWER UP FROM CIGARETTE LIGHTER OR CAR BATTERY.IT YOUR SCANNER SHOULD HAVE POWER HOOK UP CABLES FOR BATTERY AND CIGARETTE LIGHTER TO POWER UP SCANNER.