16117285451 Fuel Tank Sender Unit For BMW X3 F25 / X4 F26

16117285451 fuel tank sender unit for BMW X3 F25 and X4 F26. It is the in-tank level sensor that drives the fuel gauge and the remaining range display on these two SUV bodies, and it is reached through the access opening under the rear seat bench.

The sender floats on a stainless arm inside a plastic carrier and sweeps a film resistor track as the tank level changes. On the F25 and F26 the tank is saddle shaped, so the sender arm is longer than on a saloon and the pivot is offset towards the right hand chamber. The carrier is held by a bayonet ring and sealed with an O-ring, and the electrical connector is a sealed four pin housing that also carries the low fuel switch contact.

Applications are the X3 F25 and the X4 F26, both of which use this sender in the right hand side of the tank. The service procedure is to fold the rear seat forward, remove the access cover, disconnect the battery, unplug the sender, then turn the locking ring. Clean the tank top before opening it, because grit around the flange is the most common reason for a fuel smell in the cabin after the job.

Symptoms that point at the sender rather than the gauge are a needle that stays at full for a long time after refuelling and then drops quickly, a reading that swings when the car corners, and a low fuel warning that appears with a quarter tank still showing. On these cars the sender signal also feeds the range calculation in the iDrive menu, so an erratic remaining range figure is often the first clue, well before the needle looks wrong.

Each unit is checked for resistance at empty, quarter, half, three quarter and full positions, and the arm travel is verified against the nominal sweep. The flange O-ring is supplied.