P0442

DTC P0442 Evaporative Emission (EVAP) System Small Leak Detected






Circuit Description

The evaporative system includes the following components:

- The fuel tank.
- The EVAP vent solenoid.
- The fuel tank pressure sensor.
- The fuel pipes and hoses.
- The vapor lines.
- The fuel cap.
- The evaporative emission canister.
- The purge lines.
- The EVAP purge solenoid.

The evaporative leak detection diagnostic strategy is based on applying a vacuum to the EVAP system and monitoring the vacuum decay. The VCM monitors vacuum level via the fuel tank vacuum sensor input. At an appropriate time, the EVAP purge solenoid and the EVAP vent solenoid are turned ON, allowing the engine vacuum to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP purge solenoid turns OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period. A small leak in the system will cause DTC P0442 to be set.

Conditions for Running the DTC

- No active MAP sensor DTCs.
- No active TP sensor DTCs.
- No active VS DTCs.
- No active O2 sensor DTCs.
- No active ECT sensor DTCs.
- No active IAT sensor DTCs.
- DTC P0125 not active.
- The Fuel Level is greater than 12.5 % and 87 %.
- The ECT is between 4-30°C (39-86°F).
- The IAT is between 4-30°C (39-86°F).
- The cold start temperature difference (ECT minus IAT) is less than:
- 1.5°C (35°F)when the IAT is greater than the ECT or
- 8°C (46°F) when the ECT is greater than the IAT.
- The BARO is greater than 72 kpa.
- The change in fuel tank vacuum is less than 0.6 in. of H2O, or the change in fuel level is less than 8 %.
- The throttle position is less than 75 %.
- The vehicle speed is less than 65 mph (104 km/h).
- The fuel tank vacuum level remains above a calibrated value for a specified number of seconds.

Conditions for Setting the DTC

The EVAP system is unable to hold a specified vacuum level for a calibrated number of seconds.

Action Taken When the DTC Sets

- The VCM illuminates the MIL during the second key cycle in which the DTC sets.
- The VCM stores the conditions which were present when the DTC sets as the Freeze Frame and the Fail Records data.

Conditions for Clearing the MIL or DTC

- The MIL will turn OFF after one ignition cycle in which the diagnostic runs without a fault.
- The Freeze Frame information and the history DTC will clear after one ignition cycle in which the diagnostic runs without a fault.
- A scan tool can clear the DTC(s)..

Diagnostic Aids

Important: An accurate indication of fuel level is required for the VCM to properly pass or fail this DTC. Always diagnose fuel level sensor DTC's before performing this DTC's diagnostic table. Always check for fuel level sensor DTC's stored in history.

Check for the following conditions:

- A loose, missing, damaged, or improperly installed fuel cap.
- Missing or damaged O-rings at EVAP canister fuel vapor and purge line fittings.
- A cracked or punctured EVAP canister.
- A damaged or disconnected source vacuum line, EVAP purge line, vent hose or fuel tank vapor line.
- Incorrectly routed or defective EVAP system vacuum and vapor lines.
- A poor connection at the VCM: Inspect the harness connectors for the following conditions:
- Backed out terminals.
- Improper mating.
- Broken locks.
- Improperly formed or damaged terminals.
- A poor terminal to wire connection.
- A damaged harness: Inspect the wiring harness to the EVAP vent solenoid EVAP purge solenoid and the fuel tank pressure sensor for an intermittent open or short circuit.
- A missing or damaged weather-pack on the EVAP Purge Solenoid connector.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to set occurs. This may assist in diagnosing the condition.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

3. Inspect the service port. Make sure that the dust cap and valve core are not loose or damaged (the valve core may have left hand threads). If the service port is suspect of leakage use the following procedure:

- Disconnect the purge line from the EVAP Purge solenoid valve.
- Connect a hand vacuum pump to the service port by placing the hose/adaptor over the unthreaded end portion of the service port.
- Apply vacuum to 5 in. Hg. If the vacuum does not hold replace the service port (may require line replacement).

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. 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 (vacuum).