P0442

DTC P0442 Evaporative Emission (EVAP) Control System Small Leak Detected




Circuit Description
The evaporative system includes the following components:
- Fuel tank.
- EVAP vent solenoid.
- Fuel tank pressure sensor.
- Fuel pipes and hoses.
- Fuel vapor lines.
- Fuel cap.
- EVAP canister.
- Purge lines.
- EVAP canister purge valve.
- EVAP service port.

The evaporative emission system is checked by applying vacuum to the EVAP system and monitoring for a vacuum decay. The PCM monitors the vacuum level through the fuel tank pressure sensor signal. At an appropriate time, the EVAP canister purge valve and the EVAP vent solenoid are turned ON, allowing the engine to draw a small vacuum on the entire evaporative emission system. After the desired vacuum level has been achieved, the EVAP canister purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in vacuum level over a given time period, when all other variables remain constant. A small leak in the system will cause Diagnostic Trouble Code P0442 to be set. DTC P0442 is a type A code.

Conditions for Setting the DTC
- The BARO is greater the 72.3 kPa.
- No: MAP, TPS, IAT, ECT, EGR, EVAP, VSS, or System Voltage Diagnostic Trouble Codes.
- IAT and ECT at start up are between 3.5 °C (38 °F) and 32 °C (90 °F).
- The difference between IAT and ECT at start-up is less than 6.75 °C (12.2 °F).
- Vehicle Speed is less than or equal to 98 kph (60 mph).
- Fuel Level counts vary by less than 8 counts in a 0.125 second time frame.
- The Fuel Tank Level Sensor reads between 10 % and 90 %.
- Maximum Engine Run time is at least 540 seconds.
- The difference between the actual Fuel Tank Pressure and the expected Fuel Tank Pressure is less than the PCM's expectation.
- Fuel Tank Pressure slope is less than or equal to 1 mm (0.03 inches) of water. The above conditions are met, and the following condition is met once:
- A single 15 second vacuum decay slope and three 5 second vacuum slopes are all greater than or equal to the PCM's upper threshold.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM will record operating conditions at the time the diagnostic fails. The Freeze Frame and Failure Records buffers will store this information.
- A history Diagnostic Trouble Code is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after 3 consecutive ignition cycles in which the diagnostic runs without a fault.
- A history Diagnostic Trouble Code will clear after 40 consecutive warm up cycles without a fault.
- A Tech 2 can clear the Diagnostic Trouble Codes.

Diagnostic Aids
- A loose, missing, or damaged fuel cap.
- Missing or damaged O-rings at the fuel vapor fittings and the EVAP purge line canister fittings.
- Cracked EVAP canister.
- Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel vapor line.
- The Fuel Pressure Sensor shares a 5 Volt reference with the MAP sensor and TP sensor.

If these codes are also set, it could indicate a problem with the 5 Volt reference circuit or components itself.
- The Fuel Pressure Sensor share a ground with the MAP sensor and the TP sensor.
- Poor connection at PCM: Inspect harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
- Damaged harness: Inspect the wiring harness to the EVAP vent solenoid, the EVAP purge solenoid, and the fuel tank pressure sensor for an intermittent open or intermittent short circuit.

Check for charcoal particles. Refer to EVAP System before starting repairs.

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

Steps 1 - 5:

Steps 6 - 7:

Steps 8 - 9:

Steps 10 - 13:

Steps 14:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Chart:
1. The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the Tech 2 if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the Tech 2 for later reference.
3. If a vent solenoid or EVAP canister purge valve electrical malfunction is present, the purge system will not operate correctly. Repairing the electrical malfunction will very likely correct the condition that set Diagnostic Trouble Code P0442.
4. Checks the fuel tank pressure sensor at ambient pressure.
6. Forces the fuel tank pressure sensor to re-zero.
7. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.