We are working on my aunts 05 Trailblazer with the V6. It was having intermittent fuel sending unit issues so we replaced the fuel pump assembly. After a couple days had the same issue again where the fuel gauge went to empty for a few seconds. We were testing for connection under the hood with a power probe when things started going down hill fast. The engine went from running fine to putting itself into "power down" mode. Then while trying to figure out why it put itself into that mode the vehicle wouldnt start at all. Now we can get it to start but there is 0 throttle response and no feedback from the PCM. Any suggestions? Does the PCM need to be reflashed?