P0442

DTC P0442 Evaporative Emission System Small Leak

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

At the 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 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, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0300, P0402, P0404, P0405, P0406, P0443, P0449, P0452, P0453, P0506, P0507, P1130, P1133, P1134, P1627 and P1640 will not set.
- Intake air temperature (IAT) and engine coolant Temperature (ECT) are between 4 °C (40 °F) and 32 °C (90 °F) at engine start up.
- Barometric Pressure (BARO) is greater than 72.3 kPa.
- ECT is not more than 6.25 °C (43.3 °F) greater than the intake air temperature at engine start up.
- Intake Air Temperature (IAT) is not more than 6.25 °C (43.3 °F) greater than the Engine Coolant Temperature (ECT) at engine start up.
- Vehicle speed is less than or equal to 90 mph.
- Fuel tank level is between 10% and 90%.
- The Throttle Position (TP) sensor is less than or equal to 100%.
- The change in fuel tank pressure is less than or equal to 24.9 in H2O.
- The vapor pressure slope is less than or equal to 0.152 in H2O/sec.
- System voltage is between 11 v and 16 v.
- No fuel slosh, and the change in fuel level percent is 21 counts in 0.125 sec.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The 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.
- Coolant fan turns on.

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 40 consecutive warmup 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, 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:
- Missing or damaged O-rings at fuel vapor and EVAP purge line canister fittings.
- Cracked or punctured EVAP canister.
- Damaged source vacuum line, EVAP purge line, EVAP vent hose or fuel tank vapor line.
- Poor connection at ECM. Inspect harness connectors for the following conditions:
- Backed-out terminals
- Improper mating
- Broken locks
- Improperly formed
- Damaged terminals
- Poor terminal-to-wire connection
- Damaged harness. Inspect the wiring harness to the EVAP vent solenoid EVAP canister purge valve and the fuel tank pressure sensor for an intermittent open or short circuit.

Steps 1 - 6:

Steps 7 - 11:

Steps 12 - 13:

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.
2. 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.
3. Checks the fuel tank pressure sensor at ambient pressure.
5. Forces fuel tank pressure sensor to re-zero.
6. Verifies that the fuel tank pressure sensor accurately reacts to EVAP system pressure changes.