97 GMC Sierra 4wd

Usually battery or connections. Just work from battery back. If you have a known good battery to throw in great if not a volt meter would be very helpful right now. If you do have someone turn key while you watch volts on battery Post only. If stays around 12.20 or higher than look for corrosion cables or loose connections. If you have side post than you just have to make sure those connections are tight and clean. If battery voltages goes 11.5 or below than battery it is.

Make sure your mains are tight to engine and fuse block. Then check wire connections and voltage at the starter itself. I had to replace my starter a while back too

Hey been trying to get back to you. First time learning how to respond to questions going to email. Reply doesn't work. If you asked about the switch on the gear shifter then yes it could keep it from starting but you said it acted as though it was trying to start. That switch is either on or off it's either working or not so if it's not working and it doesn't think it's in park then it will not try to start at all. If it's working then you should be able to try to start it. You can shift into drive or reverse and see if that changes. If it doesn't act like it's trying to start it all then that's which is working. It still should be something with the starter wires excetera. PS that switch goes bad s lot but I've seen people wiggle the shifter to make it work for years until it doesn't. Don't jump to far ahead or you might miss something that's an easier fix. Disregard if this wasn't for you. I'll be here on and off if I can help you. If you don't have the ability to do electrical test then I would take battery first then starter if you don't find any loose wires to be tested and go from there

Thanks for getting back with me ! Have not figured out this site yet. My truck will sometimes get stuck in park and will not come out initially but it will eventually. I also do not have to depress the brake to shift gears which is unusual. I checked the battery and all is well. I have a friend bringing me a almost new starter for free so I am going to try that . I think these are two separate problems but figuring both out is a plus !