Mike717

Hello all, New to the forums here so I'll try to be as detailed as I can. My pops has an 08 gmc sierra 1500 4.3l v6 and Im trying to find the issue here of the engine turning over but wont start. It seems as if its deprived of fuel being a fuel issue potentially. We went to auto parts store and got the pressure valve test kit for fuel and connected it to the tap in my screenshot with key on its 60PSI and while turning over 60PSI doesn't seem to be dropping so I think the pump is fine???? Check this screenshot out - https://imgur.com/a/6rXTwdR On the top of the throttle body where I pointed out the cap is where we tested from but in that boxed area we suspect this part may be at fault. Does anyone know what it is? Also on the throttle body itself is a sensor on the left side and another just up top of that also pointed out. We've checked, cleaned and reseated the connections there no luck. Its also notable that when the issue first started as he was driving a few days ago check engine came on and says "Reduced engine power" he did stall out several times before he crawled home multiple times. It wont even start anymore, we did manage to get OD tool to check for engine light its code reporting is: P0641 "5V Reference 1 Circuit" - only 1 code no others. We think the little wire just up top of the throttle body where the test point was on the line is measuring something under that black cover perhaps its having the issue. Any feedback greatly appreciated.