Last week I fueled up my '09 HHR and headed north to Zephyrhills (about 5 hr's away). I kept switching the info readouts just to see how far I had gone, and fuel consumption (and fight boredom) I couldn't believe the incredible mileage I was getting. After over an hour into the trip I realized it was impossible. Just at that moment, the gauge jumped from full to empty, and the low fuel warning came on. The digital "distance till empty" still said 416mi (after it increased from +/-365mi.). The next day, about mid-day the gauge started working again, and has worked since then.
MY QUESTION IS: Is this something I should go to the dealer and get checked out, or just let it be? Will there possibly be an error code? It works now and without an error code, will they be able to diagnose the cause?

 

If you bring it in for service, you might want to mention PIC5363A, it might help if there are not codes stored.

 

Went on here to try to figure out this problem too - mine did it once where it stayed near full - then i ran out of gas one day, not listening to my intuition. after that it worked fine for several weeks. Then the other day it was sticking near full and then last night suddenly dropped to near empty - low fuel light on. put the odb reader on and had a new code (CEL has always been on due to a bad cat - so didn't think to check for a new code till now) - shows P0461 Fuel Level Sensor 'A' Circuit range/Performance.
At 180K I am guessing i'll be needing to replace the fuel pump to clear this up.
Separate issue of the gas pumps shutting off all the time when trying to fill the tank is another unrelated issue - haven't researched that one - wondering if others have experience that - like the fuel is going up the fill tube really quick even when tank is empty and shuts the pump off so have to wait 10 sec for it to settle down - only takes about 1/3 to 1/2 gallon at a time making filling up incredibly annoying and never knowing when the tank is near full.
I think i found the issue - joy joy https://www.chevyhhr.net/forums/prob...-insane-60631/

 

Why do you think "unrelated"? That usually means that the EVAP vent valve is blocked OR you are filling up with the engine running.