P0442
DTC P0442SYSTEM DESCRIPTION
The evaporative emission (EVAP) system is used to store fuel vapors to reduce the amount of unburned fuel from escaping into the atmosphere. The EVAP system consists of the EVAP canister, the fuel tank pressure (FTP) sensor, the EVAP lines and hoses, the EVAP canister purge solenoid valve which is normally closed, the EVAP service port, the EVAP canister vent solenoid valve which is normally open, the fuel tank, and the powertrain control module (PCM). The PCM monitors the EVAP system for circuit faults in the FTP sensor, the EVAP canister purge solenoid valve and the EVAP canister vent solenoid valve circuits. The PCM also monitors the EVAP system for small and large leaks. During the EVAP diagnostic, the PCM monitors the FTP sensor for an atmospheric pressure reading when all of the DTC parameters have been met with the engine running. The PCM will then command the EVAP canister vent solenoid valve ON, closed valve, and command the EVAP canister purge solenoid valve to a fixed duty cycle. The PCM will let the pressure drop in the fuel tank for a certain length of time, after which it will turn OFF the EVAP canister purge solenoid valve. If a correct amount of vacuum is achieved, the PCM will run the DTC P0442 diagnostic, which will monitor the decay in the vacuum of the sealed system over a calibrated amount of time. DTC P0442 sets when the vacuum decay is greater than the calibrated amount for a certain length of time due to a small leak.
CONDITIONS FOR RUNNING THE DTC
- DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0452, P0453, P0502, P0503, P0601, P0602, P1621 are not set.
- The EVAP canister vent solenoid valve is commanded ON, closed.
- The EVAP canister purge solenoid valve is commanded OFF, closed.
- The engine is running.
- The fuel level is between 15-85 percent.
- The barometric pressure (BARO) is greater than 75 kPa.
- The engine coolant temperature (ECT) and the intake air temperature (IAT) are between 4-30°C (39-86°F) at engine startup.
- The ECT and the IAT are within 8°C (15°F) of each other.
- The throttle position (TP) angle is between 7-35 percent.
- The vehicle speed is less than 113 km/h (70 mph).
- The DTC P0442 diagnostic runs once per ignition cycle after the above conditions have been met.
CONDITIONS FOR SETTING THE DTC
- If the vacuum decay is greater than 0.02 volts with low fuel level and 0.10 volts with high fuel level, FTP sensor volts per second indicating a small EVAP leak, DTC P0442 will set.
- The above condition exists longer than 15 seconds.
ACTION TAKEN WHEN THE DTC SETS
- The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
CONDITIONS FOR CLEARING THE MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.
DIAGNOSTIC AIDS
- An EVAP canister purge solenoid valve or EVAP canister vent solenoid valve circuit fault may have caused this DTC to set.
- The PCM uses the FTP sensor to detect the amount of vacuum pulled on the EVAP system during the leak diagnostic tests. Ensure that the fuel pressure sensor is not skewed by verifying the FTP sensor on the scan tool is between 2.35-2.85 volts with the ignition ON and the fuel cap removed.
- Locate the small leak with the Evaporative Emission System Tester.
- The following are possible causes of a small leak:
- The fuel cap is leaking.
- The EVAP canister vent solenoid valve is not seating correctly.
- The EVAP vent hose is loose or damaged.
- The EVAP canister is leaking.
- The fuel sender assembly O-ring is leaking.
- The fuel tank or filler neck is leaking.
- The small leak diagnostic can detect a leak greater than 0.020 of an inch in diameter.
- A condition may exist where a leak in the EVAP system only exists under a vacuum condition. By using the scan tool Purge/Seal function to create a vacuum, seal the system and observe the FTP parameter for vacuum decay, this type of leak may be detected.
TEST
