my speedometer does not work but other gauges and tach do. the indicator that shows what gear tranny is in does not work,door locks don't unlock when i park or kill engine, abs and check engine symbols are lit up, and engine has little acceleration at low speed. all seemed to happen at once. i have been kicking the brake switch on the cruise control to get it to work for the last month, been too lazy to try to adjust or clean, don't think this has caused the other problems but thought i should come clean on it.

 

Kicking the switch will destroy it. You have lost a module or the programming. Try this and tell me how you do. All newer GM vehicles may have a BCM (Body Control Module)
PCM is the Transmission module.
Put the vehicle in sunlight to keep the auto headlights off. Connect a charger to the battery to keep it charged, observing proper polarity. Put the key in the ignition and turn to run position. Observe which lights do not work on the dash. Also if your security light is on that's a good thing.
Turn the ignition off and take the key out. Put the key back in and turn to run position. all the lights in the dash (those that work) will come on. Leave the key ON for 30 mins. DO NOT use any accessories or use the windows. Put the drivers window down BEFORE you do this so if the auto locks activate you can still get in it.
After 30 minutes shut the ignition OFF, REMOVE the key and re-insert. Disconnect the battery charger and start the truck. See if it all works again. If not borrow some money and take it to the dealer. They charge an arm and butt but that will be your only alternative. You may also check for codes as the check engine light may not be working.
let me know how you fare.
John