Will not crank over

For last couple months kept acting like barely wanted to start but would always start until the other day when it did not. Had battery tested and battery is not the issue. Checked fuses and all fuses seem to be good. Seems to be getting proper ground. When I short the starter from the fuse box the starter turns over and the engine will start but does not stay running as it is not being fed any gas. I switched IGN relays and starter relays out with other relays and that did not seem to change anything. Tried book method to reset antitheft system. Have left key on and disconnected pcm fuse for 5 min then tried but no success. Seen online to try to clear codes with OBD reader. When I hook up the OBD reader wont read codes says link error. I believe issue is being caused by either the lock cylinder or the ignition switch itself. Any ideas?