Fuel Pressure Sensor / Fuel Temperature Sensor

Courtesy of VOLVO CARS CORPORATION

Overview 

The fuel pressure, fuel temperature sensor is combined and consists of both the fuel pressure sensor and the fuel temperature sensor. The sensor detects the fuel pressure (the absolute pressure) and the temperature of the fuel in the fuel rail.

The fuel pressure sensor is located on the fuel rail's end.

The fuel pressure-/fuel temperature sensor can be diagnosed by the engine control module (ECM) and its signals (pressure and temperature) can be read off.

Fuel pressure sensor 

The pressure sensor is a Piezo resistive type resistor, the resistance of which changes with the pressure. Depending on the pressure in the fuel rail, an analog signal of 0 - 5 V is transmitted to the engine control module (ECM). Low pressure results in low voltage, high pressure gives high voltage.

The engine control module (ECM) then uses this signal to adjust the pressure in the fuel rail using the fuel pump control module. See also: FUNCTION  

The pressure sensor is supplied with 5 V and grounded in the engine control module (ECM). The pressure sensor transmits a signal indicating the fuel pressure to the engine control module (ECM) on a separate cable.

HINT: The relative pressure (absolute pressure minus atmospheric pressure) is displayed when reading off the fuel pressure via a manometer connected to the fuel rail. 

Fuel temperature sensor 

The temperature sensor is an NTC sensor. The sensor is supplied with voltage (signal) from and grounded in the engine control module (ECM).

The resistance in the sensor changes according to the temperature of the fuel. This provides the engine control module (ECM) with a signal of between 0 - 5 V. Low temperature results in high voltage (high resistance). High temperature results in low voltage (low resistance).

The engine control module (ECM) uses the signal to calculate the volume of the fuel.