P0171 CEL Code
 

Got this CEL code after filling up my Santa Fe. I was filling up and changed grip on the fuel nozzle. The pump shut off and I thought it was because I changed hand position and the nozzle slipped. So I pressed the nozzle again and it very quickly shut off again. I realized the tank was full and I had just "topped" it up. It wasn't much, maybe 1/2 litre at most. I never top the tank up since I've heard it can cause problems with the emissions system. I drove home (about 35 Km) and noticed a bit of rough idling when I came to stop lights/signs. Next day I reset the code and drove the car. No rough idle. The P0171 CEL code has not come back on after several trips. So I think the problem was topping up the fuel tank. I have read on another thread that replacing the charcoal canister fixed the P0171 code. I suspect the problem in that case was overfilling that damaged/flooded the canister.

Hello and welcome to the forum.

Microsys00:
P0171 indicates a lean running engine. With the tank overfilled lean running is less likely than rich running. Lean running is most often caused by a vacuum leak between the MAF sensor and the intake valves.

For now I wouldn't worry because the code has not come back. A code is set when the same error happens 2 x in sequence. Whatever has caused this in your car is being handled by the PCM computer in sufficient manner.

Welcome to aboard.

Hello and welcome!