I Swapped a 5.3 lm7 into my 2000 tahoe z71 obs, i cranked it and it started right up and shut off, i used the hptuners to set the vats setting to "none" then clicked "write entire" and security light turned off and now truck wont start, i did this about 5 times and still wont start, i set the vats to serial again then it starts right up and security light starts flashing again. Any advice? been at this for the past three days