I am looking at buying a 2004 Chevrolet Silverado 2500 diesel. I am told the airbag light is on, the sales guy told me it is the sensor ? I asked for a price at the local Chevrolet garage, the parts guy said the light could be a number of more costly things. Any way I can check this, as I have said I have not bought the truck yet.

thank you in advance

A local Autozone can do a OBDII scan for free. That may help. They may need to use a scanner capable of scanning the Air bag system.

You can try Before you buy a used car, get the facts - Carfacts.com (http://www.carfacts.com) to see if the car was in an accident.

Airbags are costly to replace. It could have deployed in an accident and not replaced. Costly.

KeepItSimpleStupid

Thanks for the advice, I have looked at carfax, the truck is clean in all departments.
Taking the truck to an Autozone would be tricky, the Silverado does not have a plate.

OK, then take the scanner to it. They allow you to use one with a deposit, for free.

Good thinking, I will do that. Will any OBD II scanner be able to check the air bag light / sensor ?

Not necessarily. Call and ask. They typically have Actron scanners. Here is a blurb from Actron's website:

Actron® (http://www.actron.com/faq_detail.php?pid=16298&id=17)