Ok so I have a 2008 hhr started loosing power and died got it started back and ran with low power for just a few minutes and died and wouldn't start back the temperature gauge reads hot but it's not running hot towed it home turned the key on temperature hand went straight to red and says cool down mode so replaced sensor and the same thing with the new one so not sure if it's the reason it won't start but got to checking stuff have fuel pressure and spark but no injector pulse with noid hooked up.the temperature gauge will bounce cold to hot if u leave the key on for a little while but it never stays on cold just returns to hot every time

 

That's an instresting problem. Are there any codes in the system? The temp gauge problem makes me think of a ground issue.

 

My brain is saying either the main ECM ground at the radiator support (driver side), or the old loose fuse box thing.

 

No codes at all I guess today I will check ground I'm not sure if the two are related just kinda of weird it heppend at the same time and that new sensor did the same thing

 

Ok so I got the car running and not real sure what we did but now when I turn the a.c. on the rpms jump to like 4000

 

Ground wires, fuse box halves loose, relays loose in fuse box.