Voltage should measure 1.25 kPa (0.5 volts). When the air pressure in the tank is 1.25 kPa (4.5 inches Hg), the sensor output Of the sensor will measure 1.3-1.7 volts. The outside air pressure, such as when the fuel fill cap is removed, the output voltage When the air pressure in the fuel tank is equal to The sensor provides a signal voltageīetween 0.1-4.9 volts to the PCM. Reference voltage and ground to the sensor. The sensor mounts at the top of the fuel tank sending unit. Pressure, or vacuum, in the fuel tank and the outside air pressure. Purge Valve Leak Test P1441 A stuck open or partially open purge valve.įuel Tank Pressure Sensor: The fuel tank pressure (FTP) sensor measures the difference between the air Vacuum Decay Test Small Leak Test: P0442 A small leak somewhere in the system,Ĭanister Vent Restriction Test: P0446 A restriction in the EVAP vent system Weak Vacuum Test and Large Leak Test: P0440 A large leak, above. If the PCM detects an increase, a malfunction is indicated by setting DTCĭiagnostic Test Failure. This isĪccomplished by sealing the EVAP system purge valve and the EVAP vent valve andĪllowing the PCM to monitor the FTP sensor. This tests for small leaks to the intake manifold. Too high, a malfunction is indicated by setting DTC P0446. Period of time and conditions have been met, this test will pass. The FTP sensor looks for sufficient vacuum from the engine intake manifold. This tests for a restriction in the EVAP vent system. If the calculation indicates that a leak is present, the Small Leak Test will fail. Vacuum has decayed to near zero, the PCM subtracts the measured slope from the vacuum decay toĬalculate the leak size. This test is used to determine the vacuum leak size. If vacuum decay is still more than aĬalibrated value, a malfunction is indicated by setting DTC P0442. If the decay rate is more than aĬalibrated value, another Vacuum Decay Test will be initiated. Measuring the change in the fuel tank pressure over a period of time. This tests for small leaks in the EVAP system. If Weak Vacuum does not pass, the test continues through this ignition cycle. The FTP sensor looks for high tank vacuum over a period of time. This tests the EVAP system after the Weak Vacuum Test has failed. If the PCM does not detect an increase, a malfunction is indicated by setting DTC P0440. The FTP sensor value should increase over a period Restriction in the vacuum supply to the fuel tank. Pressure (FTP) sensor detects a low fuel tank pressure resulting from a large vacuum leak or a This tests for large leaks and blockages in the EVAP system. The EVAP diagnostic tests include the following tests:
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If the diagnostic fails a sub-test, the PCM stores aĭiagnostic trouble code (DTC) in order to indicate the type of fault detected. Sub-tests in order to detect the fault conditions. The enhanced evaporative system diagnostic conducts Usually a fault can only be detected after a cold start with a trip of sufficient length andĭriving conditions to run the needed tests. If there is a leak, the system either will not achieve a vacuum, or a vacuum cannotīe maintained. The vacuum remains for a specified period of time, then there are no evaporative leaks, and a PASS is The powertrain control module (PCM) then monitors the ability of the system to maintain the vacuum. System integrity by applying a vacuum signal, ported or manifold, to the fuel tank in order to create a The system is required in order to detect the evaporative fuel system leaks as small as 0.040 inchīetween the fuel filler cap and the EVAP canister purge valve. When the engine is able to use the extra fuel vapor, the intake air flow purges theįuel vapor from the carbon element and then the normal combustion process consumes the fuel vapor. The EVAP canister stores the vapors until the engine is able to use The EVAP transfers the fuel vapors from the sealed fuel tank to an activated carbon The evaporative emission (EVAP) control system limits the fuel vapors from escaping into theĪtmosphere. Read Some Popular EVAP System Questions And Answers Evaporative Emissions System (EVAP) Description