P0442

P0442 Evaporative Emission System Small Leak

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

The EVAP emission system is checked by applying vacuum to the EVAP emission system and monitoring for a vacuum decay. The powertrain control module (PCM)/engine control module (ECM) monitors the vacuum level through the fuel tank pressure sensor signal.

At the appropriate time, the EVAP emission canister purge valve and the EVAP emission 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 emission canister purge valve is turned OFF, sealing the system. A leak is detected by monitoring for a decrease in the vacuum level over a given time period, when all other variables remain constant. A small leak in the system will cause DTC P0442 to be set.

Conditions for Setting the DTC
- DTC(s) P0106, P0107, P0108, P0112, P0113, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0449, P0452, P0453, P0506, P0507, P1130, P1133, P1134, P1171, P1404, P1627 and P1640 will not set.

- EVAP Service Bay Test:
- Barometric Pressure (Baro) is greater than 72.3 kPa.
- Vehicle is in idle.
- Vehicle Speed Sensor (VSS) is less than 6 mph (10 kph).
- Engine speed is less than 1700 rpm.
- Throttle Position (TP) sensor is less than 1.7%.

- FTP Mode:
- Engine Coolant Temperature (ECT) and Intake Air Temperature (IAT) are between 39 °F (4 °C) and 95 °F (35 °C) at Engine start up.
- The value of ECT minus IAT is less than 46 °F (8 °C) or the value of IAT minus ECT is less than 59 °F (15 °C) at Engine start up.
- Vehicle Speed is less than 90 mph (145 kph).
- The change in the MAP is less than 5 kPa.
- The TP Sensor is less than 2.0%.
- The change in RPM is less than 100 rpm.
- The change in the AD fuel is less than 12.
- Vapor pressure slope is 0.10 in H2O/sec.
- Fuel level is between 15% and 85%.
- System voltage is between 11 volts and 16 volts.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The PCM/ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn off after three consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 80 consecutive warm-up cycles without a fault.
- DTC(s) can be cleared by using the scan tool.

Diagnostic Aids
Although this DTC is considered a type A diagnostic (refer to "Powertrain Control Module/Engine Control Module"), it acts like a type B diagnostic under certain conditions. Whenever this diagnostic reports the system has passed, or if the battery is disconnected, the diagnostic must fail twice before setting a DTC. The initial failure is not reported to the diagnostic executive or displayed on a scan tool. A passing system always reports to the diagnostic executive immediately.

Check for the following conditions:
1. Missing or damaged O-rings at fuel vapor and EVAP emission purge line canister fittings.
2. Cracked or punctured EVAP emission canister.
3. Damaged source vacuum line, EVAP emission purge line, EVAP emission vent hose or fuel tank vapor line.
4. Poor connection at PCM/ECM. Inspect harness connectors for the following conditions:
- Backed-out terminals
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection

5. Damaged harness. Inspect the wiring harness to the EVAP emission vent solenoid EVAP emission canister purge valve and the fuel tank pressure sensor for an intermittent open or short circuit.

Step 1 - 5:

Step 6 - 10:

Step 11 - 12:

Test Description
Number(s) below refer to the step number(s) on the Diagnostic Table.
1. The On-Board Diagnostic (OBD II) System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool 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 DTC P0442.
4. Checks the fuel tank pressure sensor at ambient pressure.
5. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.