Gas filling nozzle clicks off every 2 seconds when refueling

The Evaporative emissions vent valve back under the vehicle near the fuel tank is bad or you have a pinched hose somewhere under there ,or the vapor canister came apart an is clogged ! Fuel Filling Troubleshooting Vent Solenoid Fixing Car Where The Gas Pump Keeps Shutting Off As You Try To Refuel

It could be an emmissions problem. Sometimes even the gas cap being loose can cause a code. Make sure to tighten the cap when done refuelling...you should hear repetitive clicks when its tight. Other components related to code p0172 are o2 sensor(bank 1) and catalytic converters. Hope this helps!

a suggested have the filler and recovery and evap system of the tank filler tube checked out ..could be perished seals or piping
other thoughts
some gas stations fuel pump sniffers can be more sensitive to shut offs than others....the pump sensor is supposed to be tested adjustable or sensor replaced regular intervals
these days the operator wait till there enough complaints before doing anything

the new model cars seem to have more filler neck filling issues
than in the past
could be the smaller diameter of the pump nozzle

could be the temperature of the day fuming the gas in the cars filler tube

Did the car store or was not used for a while or been in an accident I think the (float ) level for the tank has been moved or broken Like in a toilet if the float does not work water will run for ever In a mitsubishi shogun pajero the tank is easily approcheable on the rear of the seat I ' m not sure on the BMW Best ask and get your mechanic to change it Good luck

My buddy Charlie says your smaller vent line is either plugged or crimped. don-ohio

replace the filler unit

Don't stick it in so far.

you have a faulty antirollover valve witch is located in the gas tank.it is stuck in the shut off position.explaning wy you can't put gas in it.
what is the code that keeps setting?
the antirollover valve is a plastic spring loaded ball that prevents fuel spillage from the tank in the case that your vehicle should be upsidedown. these valves have been known to fail ,causing problems refueling the vehicle.

you have a breather line that could be clogged. Try not putting the nozzle all the way in when refueling so air can get out.

The ORVR (On-Board Refueling Vapor Recovery) system consists of a unique fuel tank, flow management valve, fluid control valve, one-way check valve and vapor canister.

The ORVR (On-Board Refueling Vapor Recovery) system is used to remove excess fuel tank vapors. This is done while the vehicle is being refueled..

Fuel flowing into the fuel filler tube (approx. 1 inches I.D.) creates an aspiration effect drawing air into the fuel fill tube. During refueling, the fuel tank is vented to the EVAP canister to capture escaping vapors. With air flowing into the filler tube, there are no fuel vapors escaping to the atmosphere. Once the refueling vapors are captured by the EVAP canister, the vehicle's computer controlled purge system draws vapor out of the canister for the engine to burn. The vapor flow is metered by the purge solenoid so that there is no, or minimal impact on driveability or tailpipe emissions.

As fuel starts to flow through the fuel fill tube, it opens the normally closed check valve and enters the fuel tank. Vapor or air is expelled from the tank through the control valve and on to the vapor canister. Vapor is absorbed in the EVAP canister until vapor flow in the lines stops. This stoppage occurs following fuel shut-off, or by having the fuel level in the tank rise high enough to close the control valve. This control valve contains a float that rises to seal the large diameter vent path to the EVAP canister. At this point in the refueling process, fuel tank pressure increases, the check valve closes (preventing liquid fuel from spiting back at the operator), and fuel then rises up the fuel filler tube to shut off the dispensing nozzle.