LR3/Disco 3
protect the engine from overheating.
ENGINE OIL TEMPERATURE SENSOR
The oil temperature sensor is located in the engine sump. The temperature sensor is a NTC type which operates in the -
30 Degrees Celsius to +150 Degrees Celsius temperature range.
Oil Temperature Sensor Response
FUEL RAIL TEMPERATURE SENSOR
The fuel rail temperature sensor is located on the LP return line.
The sensor is an NTC sensor which is connected to the ECM by two wires. The ECM fuel temperature sensor circuit
consists of an internal voltage divider circuit which incorporates an NTC thermistor. As the fuel temperature rises the
resistance through the sensor decreases. The output from the sensor is the change in voltage as the thermistor allows
more current to pass to earth relative to the temperature of the fuel.
The ECM monitors the fuel temperature constantly. If the fuel temperature exceeds 85°Celsius (185°F), the ECM invokes
an engine 'derate' strategy. This reduces the amount of fuel delivered to the injectors in order to allow the fuel to cool.
When this occurs, the driver may notice a loss of performance.
Further fuel cooling is available by a bi-metallic valve diverting fuel through the fuel cooler when the fuel reaches a
predetermined temperature. In hot climate markets, an electrically operated cooling fan is positioned in the air intake
ducting to the fuel cooler. This is controlled by a thermostatic switch, which switches the fan on and off when the fuel
reaches a predetermined temperature.
The wires to the fuel sensor are monitored by the ECM for short and open circuit. The ECM also monitors the 5V supply.
If a failure occurs a fault is recorded in the ECM memory and the ECM uses a default fuel pressure value.
If the ECM registers an 'out of range' deviation between the pressure signal from the sensor and the pre-programmed 'set
point' a fault is stored in the ECM memory. Depending on the extent of the deviation, the ECM will reduce the injection
quantity, stop the engine immediately or prevent further engine starting.
BRAKE LIGHT SWITCH
Temperature Degrees Celsius Resistance Ohms
60
620
90
255
120
117
150
60
