BMW 840i Fuel Pressure Sensor Replacement Cost

A technician will begin diagnosis of a faulty fuel temperature sensor by running a diagnostic scan with a scan tool connected to the vehicle's data port. The scan will not tell the technician if the sensor is bad, but it can reveal if the circuit for the sensor has a fault in it. If the scan is positive, the technician will access the sensor, unplug the harness wires, and test the sensor as well as the wire harness plugs. Using a multimeter, the technician will check the resistance reading of the temperature sensor. If the readings are off, the sensor needs to be replaced. If the readings are normal, the harness is checked for continuity with the multimeter.

To replace the fuel temperature sensor in most vehicles, a technician must remove the fuel pump assembly from the fuel tank. First, the technician will relieve the residual pressure in the fuel system by disabling the fuel pump (usually by removing a fuse) and cranking the ignition. Then the battery is disconnected. On some cars and SUVs, the top of the fuel tank and the fuel pump assembly are accessible from inside the passenger compartment. If this is the case, the technician removes the back seat and an access cover in the floor below. On trucks, and on many cars, the fuel tank must be removed from underneath the vehicle in order to gain access to the fuel pump assembly. In either case, once access to the fuel pump assembly is achieved, the technician will unplug the wiring harness connectors from the top of the assembly. The fuel lines are detached, often using a special tool for the connectors. The technician will remove the retaining ring that holds the fuel pump assembly in place and pull the assembly out of the tank. The fuel temperature sensor is unplugged from the assembly and detached. A new sensor is installed in its place. The pump is inserted into the tank, secured, and plugged in. If the fuel tank was removed from the vehicle, it is reinstalled. The fuel system is enabled and the system is tested.

RepairPal recommends installing a new fuel pump assembly gasket when a fuel temperature sensor is being replaced. Also, any mounting hardware for the fuel tank that might be compromised should also be replaced.

The electrical system on the vehicle should be disabled to prevent accidental arcing of wires during the repair that might cause the open fuel system to ignite.

If the fuel pump assembly is easily accessible underneath the rear seat of a vehicle, someone with intermediate to advanced DIY skills might be able to tackle the job. A diagnostic scan is necessary and experience with a multimeter is needed to avoid replacing a sensor that is not bad. If the fuel tank needs to be removed from the vehicle, the repair should be left to a qualified technician at a trusted repair shop.