P0442

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 Of 3):

Diagnostic Chart (Part 3 Of 3):

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) tests the Evaporative Emission (EVAP) system for the following conditions:
^ Large and small leaks (P0440 and P0442)
^ Excess vacuum (P0446)
^ Purge flow during non-commanded conditions (P1441)
^ Fuel pressure sensor and fuel level sensor faults (P0452, P0453, P0462 and P0463)
^ EVAP purge and vent valve faults (P0443 and P0449)

The PCM monitors the amount of vacuum in the EVAP system by monitoring the fuel tank pressure sensor. For this Diagnostic Trouble Code (DTC), the PCM turns ON both the EVAP purge valve and the EVAP vent valve when the Conditions for Running the DTC are met. This applies an engine vacuum to a closed EVAP system. The PCM turns OFF the EVAP purge valve when the system reaches the correct amount of vacuum. With the EVAP purge valve OFF and with the EVAP vent valve ON, the EVAP system should hold the vacuum in the EVAP system. This test will indicate a small leak if the EVAP system fails to hold enough vacuum for a specific length of time. This DTC will set after two consecutive failures of the above test.

CONDITIONS FOR RUNNING THE DTC
^ None of the following DTCs are present:
- Fuel trim
- Fuel injector circuit
- Misfire
- Exhaust Gas Recirculation (EGR) system
- Secondary Air Injection (AIR) system
- Vehicle Speed Sensor (VSS)
- Throttle Position (TP) sensor
- Heated Oxygen Sensor (HO2S)
- Intake Air Temperature (IAT) sensor
- Manifold Absolute Pressure (MAP) sensor
- Engine Coolant Temperature (ECT) sensor
- Mass Air Flow (MAF) sensor
^ The battery voltage is between 5-18 volts.
^ The Barometric Pressure (BARO) is more than 75 kPa.
^ The fuel level is between 15-85 percent of full capacity for at least 10 seconds continuously. The time limit is required because fuel sloshing within the tank may cause the fuel level indication to vary outside the fuel level limits.
^ The ECT at start up was between 4°C and 30°C (40°F and 86°F).
^ The IAT at start up was between 4°C and 30°C (40°F and 86°F).
^ The ECT is not more than 8°C (47°F) more than or 2°C (36°F) less than the IAT at start up.

CONDITIONS FOR SETTING THE DTC

IMPORTANT: This DTC does NOT report a first failed test. A first fail of this DTC will have a scan tool status as Not Run. Use the scan tool data display parameter EVAP Test Result in order to determine if this DTC has failed or passed for this ignition cycle.

The vacuum in the EVAP system decays or leaks too fast.

DIAGNOSTIC AIDS

IMPORTANT: An accurate indication of fuel level is required for the PCM to properly Pass or Fail this DTC. Always diagnose fuel level sensor DTCs before performing this diagnosis. Always check for fuel level sensor DTCs stored as history.

Perform a physical inspection of the EVAP system. Check for the following conditions:
^ A loose, missing, defective, or incorrect fuel tank cap
^ Any incorrectly routed or defective EVAP system vacuum and vapor lines
^ A malfunctioning or damaged vapor canister

Check for charcoal release from the vapor canister. Refer to EVAP System Cleaning.

If the problem is intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
3. Inspect the service port. Make sure that the valve core is not loose or damaged. The valve core may have left hand threads.
4. If the vehicle passes the Service Bay Test then an intermittent leak had occurred. Check the fuel tank cap for a possible loose or leaking condition that may have caused this DTC to set.
If the Service Bay Test can not be run, proceed to step 5. If a fault is not currently present the diagnostic table steps will return you to step 3.
9. Refer to the information supplied with the EVAP pressure/purge diagnostic cart on proper setup and adjustment procedures.
13. If a leak was not found in step 9, and the vehicle is equipped with on-board refueling vapor recovery, connect the EVAP pressure/purge diagnostic station with the fuel cap adaptor to the fuel tank filler neck and repeat step 9. These vehicles are equipped with a check valve at the base of the filler tube which may not allow pressure from the EVAP service port to be applied to the filler tube and the fuel cap.
An EVAP pressure sensor that does not correctly respond to pressure or vacuum will cause this DTC to set.
The EVAP pressure sensor monitors a range from +7.5 in H2O of pressure to -17.5 in H2O of pressure or vacuum.