abs?

i have an 03 alero 2.2 with 80k on it. yeaterday the check engine, abs and trac off light came on at the same time. i took it to have the codes read and they said no codes came up. the dealer said it might be an abs issue that wouldnt come up on a simple code scan. i have noticed a shuddering in the brakes recently. is this related?

If the SES and ABS lights came on it should have a code in the history... maybe a better scans needed.

I'd just drive it for a while longer, one of the wheel sensors are probly goin south, it's just best to know exactly which one before you start replacing things randomly.

The shuddering you're feeling is likely to be warped brake rotors. This is another common problem on the Alero. You'll have to replace them to get rid of the shuddering. (I'm presuming here that this only occurs under braking conditions)
It's probably not related to your abs/trac off lights. Those are probably a wheel speed sensor gone bad. They can be tested individually at each wheel with a multi-meter. Also, not all scanners are capable of scanning ABS systems. Be sure to have your system scanned with an ABS capable scanner to read ABS related codes.