Description

Fuel Temperature Sensor Description

1. Fault Codes:
Fuel Temperature Sensor Circuit High Input P0183
Fuel Temperature Sensor Circuit Low Input P0182
Fuel Temperature Sensor Rationality Check P0181

2. Monitoring Procedure

Range Check
Problems with the fuel temperature sensor are detected using a range test.
The range test tests for input values outside expected limits. If this test is not passed then the appropriate fault count will be incremented, otherwise it will be decremented.
If the count reaches a given threshold then a fault is present.
While fault counting is in progress a back-up value of fuel temperature will be supplied to avoid the problems of incorrect values reaching the rest of the system.

Rationality Check
The test on the fuel temperature sensor comprises of comparing the output from the fuel temperature sensor with a tolerance band based around the value of coolant temperature.

A fuel temperature test will check that the sensor does not have altered resistance characteristic or the sensor has not fallen off.

3. Primary Detection Parameter
Fuel Temperature - measured as thermistor voltage.

4. Fault Criteria Limits
Fuel Temperature - Low voltage (out of range)
< 0.0585 V (i.e. > 145° C)
Fuel Temperature - High voltage (out of range)
> 4.895 V (i.e. < -45° C)
Error between fuel temperature and coolant temperature
> 20° C or < -120° C

5. Monitoring Conditions
The range check will take place whenever there is power to the ECM.
The rationality check will take place once the engine has been running for a time > 40 secs.

6. Monitoring Time Length / Frequency of Checks
The frequency of the Fuel Thermistor diagnostic is 2Hz.

7. Criteria for Storing Fault Code
Two successive trips where the fuel thermistor diagnostic indicates a failed fuel temperature sensor.

8. Criteria for Illuminating MIL
Two successive trips where the fuel thermistor diagnostic indicates a failed fuel temperature sensor.

9. Criteria for Determining Out of Range Input Signals
The fuel temperature thermistor is subject to range testing as above.