P0442

Diagnostic Chart:

The evaporative emission (EVAP) system Is used to store fuel vapors as to reduce the amount of unburned fuel from escaping Into the atmosphere The EVAP system consists of the EVAP canister, fuel tank pressure (FTP) sensor, EVAP lines and hoses. EVAP purge solenoid (normally closed), EVAP service port, EVAP vent solenoid (normally open) and fuel tank. The ECM monitors the EVAP system for circuit faults in the EVAP purge solenoid, EVAP vent solenoid and FTP sensor circuits. The ECM also monitors the EVAP system for leaks (between EVAP vent and purge solenoid). When certain conditions have been met. the ECM will perform an EVAP diagnostic lest at idle with no vehicle speed, which will require a five consecutive phase (A, B, C, D and F) test. DTC P0442 will set if vacuum decays too quickly during Phase E of the EVAP diagnostic system test indicating a small EVAP system leak.

DTC PARAMETERS
DTC P0442 will set if the vacuum decay is greater than a calibration amount over a 3 second period during phase F of the EVAP diagnostic system test indicating a small EVAP leak when:
^ Condition exists for the entire phase F of 3 seconds
^ EVAP purge solenoid is commanded Off
^ EVAP vent solenoid is commanded On
^ Engine is at idle
^ Vehicle speed 0 mph
^ Engine load is less than 35%
^ Main relay voltage is greater than 10.0 volts
^ ECT at engine startup is between 4°C and 55°C (40° and 131°F)
^ IAT is between 4°C and 60°C (40° and 140°F)
^ Fuel tank pressure must be within -13.5 to 6.75 mmHg (-7.23 to 3.61 in H2O) to enable test
^ Long term fuel trim cells learned (if not learned, engine must run longer than 16 minutes and 45)
^ Fuel level is between 9.1 and 50.7 L (2.4 and 13.4 gallons)
^ No ECT. EVAP purge solenoid, EVAP vent solenoid, fuel tank pressure, idle speed HO2S, MAF, system voltage, throttle actuator, TP sensor or vehicle speed
^ DTCs have been set.

The entire EVAP diagnostic test will take about 16 seconds to complete when no errors have been detected. If the P0442 diagnostic fails, the rest of the EVAP diagnostic test is aborted and not run again in the ignition cycle.

If an EVAP diagnostic test is aborted due to changing enable criteria, the ECM will run the entire EVAP diagnostic test up to 10 times per ignition cycle.

P0442 is a type B DTC.

DIAGNOSTIC AIDS

IMPORTANT:
^ If DTC P0440. P0442, P0446 or P0496 is set. EVAP special functions on Scan tool will not be allowed. Clear DTCs before performing these tests.
^ The ECM uses the fuel tank pressure sensor to detect the vapor in the fuel tank during all parts of the EVAP diagnostic system test. Make sure the fuel tank pressure sensor is not skewed by verifying FTP SENSOR on Scan tool is between 1.40 and 1.60 volts with ignition On, engine Off and fuel cap removed.

Use the EVAP Pressure/Purge Diagnostic Chart and Ultrasonic Leak Detector to locate the small leak. Follow operating instructions in the "EVAP System Description".

Refer to "EVAP System Description" for a complete EVAP diagnostic test description.

Possible causes of a small EVAP leak:
^ Fuel cap leaking
^ EVAP vent solenoid valve not fully seating
^ EVAP service port valve leaking
^ EVAP line/hose connections leaking
^ Primary or secondary fuel sender O-ring leaking
^ Fuel tank pressure sensor seal leaking




USE THE EVAP SYSTEM PICTURE, WHICH WILL POINT TO POSSIBLE LEAK AREAS.