Description

Fuel Tank Pressure Sensor Monitor Description

1. Fault Codes:
Fuel tank pressure sensor low fault: P0452
Fuel tank pressure sensor high fault: P0453
Fuel tank pressure sensor performance fault: P0451

2. Monitoring Procedure

Summary
The resistance of the fuel tank pressure sensor changes in relation to the pressure difference between the fuel tank and ambient. Through connection to the input resistor networks of the ECM any disconnection of the sensor can generate both high and low input voltages, which are outside the normal operating voltage range. These are detected to diagnose a fuel tank pressure fault in the system.

Range Test
If the value of FUEL TANK PRESS VOLTS is less than FUEL TANK PRESS DIAG MIN VOLT THR or more than FUEL TANK PRESS DIAG MAX VOLT THR, then an appropriate fault counter is incremented up to a limit of fuel tank pressure diagnostic fault limit. Otherwise the fault counter is decremented down to a limit of zero. If the fault counter reaches the limit then a fuel tank pressure sensor fault is present.

Rationality Test
The test on the fuel tank pressure sensor comprises of comparing the output from the fuel tank pressure sensor with a tolerance band around ambient pressure. This is done during conditions of minimal vapor generation within the fuel tank.

3. Primary Detection Parameter
Fuel tank pressure - Measured in volts, the outcome of a potential divider calculation.

4. Fault Criteria Limits
Fuel Tank Pressure - Low out of range 0V
Fuel Tank Pressure - High out of range 6V
Error between fuel tank pressure and ambient pressure > 1 kPa or < -0.3 kPa

5. Monitoring Conditions
The range test will take place when the canister closure valve is open.
The rationality check will take place when the coolant temperature is between two thresholds, air temperature is between two thresholds, purge flow rate is below a threshold and the canister closure valve is open.

6. Monitoring Time Length / Frequency of Checks
The frequency of the fuel tank pressure diagnostic is 40Hz.

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

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

9. Criteria for Determining Out of Range Input Signals
The fuel tank pressure sensor is subject to the range test above.