Wrangler 4WD L4-150 2.5L VIN P MFI (1998)
Fuel Level Sensor: Description and Operation
The fuel gauge sending unit (fuel level sensor) is attached to the side of the fuel pump module. The sending unit consists of a float, an arm, and a
variable resistor (track). The resistor track is used to send electrical signals to the Powertrain Control Module (PCM) for fuel gauge operation and for
OBD II emission requirements.
For fuel gauge operation: As fuel level increases, the float and arm move up. This decreases the sending unit resistance, causing the fuel gauge to read
full. As fuel level decreases, the float and arm move down. This increases the sending unit resistance causing the fuel gauge to read empty.
After this fuel level signal is sent to the PCM, the PCM will transmit the data across the CCD bus circuits to the instrument panel. Here it is translated
into the appropriate fuel gauge level reading.
For OBD II emission monitor requirements: A voltage signal is sent from the resistor track on the sending unit to the PCM to indicate fuel level. The
purpose of this feature is to prevent the OBD II system from recording(setting false misfire and fuel system monitor trouble codes. The feature is
activated if the fuel level in the tank is less than approximately 15 percent of its rated capacity. If equipped with a Leak Detection Pump (EVAP system
monitor), this feature will also be activated if the fuel level in the tank is more than approximately 85 percent of its rated capacity.
