check engine light???

OK...this is kind of weird...
yesterday when i started my 200o tahoe limited i noticed the orange indicator that lets you know what gear you are in wasnt illuminated...i turned the truck off and started her again and it was back on...when i accelerated the truck was sluggish and the check engine light came on...i turned my tahoe off and restarted her...she drove normally but the check engine light is now on all the time...does anyone know what the problem could be and if not does anyone know where i can get the diagnostic done for free possibly...i would take it to the chevy dealer but i kind of hate the dealership...they always try to get over on you
ANY HELP WOULD BE GREAT
thanks

Got an AutoZone nearby? I've always heard they will hook up a code reader and scan the code(s) that are causing the check engine light for free. I bought a code reader a while back for like $90. You can probably find one cheaper than that. It's been a good investment for me. I've used it a few times already and a couple times on my friends vehicles.

your PNRDL switch on the tranny is probably shot. but get it scanned before replacing any parts.