'05 2.0 golf GLS cooling problem or fuel problem?

[Herbie91]

2005 Golf GLS 2.0, mom's car.
83k miles. she drives 3 miles a day.... max.

Her engine light is on and has trouble starting it sometimes, usually if it's been sitting after a medium length drive (she thinks). took it to my mechanic and had it scanned. I lost the code number, but he said is was a thermostat malfunction. even though the temp gauge is working and seems to be accurate so he cleared the light. now the lights back on again and it's having a harder time starting. this doesn't happen every time she starts the car tho, so i guess she's been comfortable living with it for the time being.

i should mention, she (mom) believes it's a fuel issue. the light goes away "when she puts gas in it" and comes back on once the tank gets closer to empty. BUT, none of the evidence i'm given says anything about fuel. but, when she was crankin it to try and start it earlier is smelt a little like gas in the garage. it didnt start... cranked it a few more times and it kicked over. could this be a clogged fuel filter? same thing happened to my '67 bug all the time.

me on the other hand wants to fix this bitch before it gets worse (like it always does)
after researching the problem with out the code number, im thinking the thermostat is stuck open... or maybe this has something to do with the temp sensor... even though the readout looks normal. and there doesnt seems to be any other issues with the cooling system apart from the "iffy" code from my mechanic.

any help would be awesome. i'll deal with the pissed middle aged single mother, you guys help me with the car.

[Herbie91]

problem solved. replacing thermostat and coolant temp sensor.

[Anony00GT]

problem solved. replacing thermostat and coolant temp sensor.

Yep. Probably the ever-so-common fault code P2181.

Faulty temp sensor will cause starting issues and the fuel smell