P2420
DTC P2420 Evaporative Emission Pressure Switching Valve Stuck OFFMalfunction Detection Condition:
DTC SUMMARY
HINT: The vent valve is built into the canister pump module.
DESCRIPTION
NOTE: In this vehicle's EVAP system, turning ON the vent valve does not seal off the EVAP system. To check for leaks in the EVAP system, disconnect the air inlet vent hose and apply pressure from the atmosphere side of the canister.
While the engine is running, if a predetermined condition (closed loop, etc.) is met, the purge VSV is opened by the ECM and stored fuel vapors in the canister are purged to the intake manifold. The ECM changes the duty cycle ratio of the purge VSV to control purge flow volume.
The purge flow volume is also determined by the intake manifold pressure. Atmospheric pressure is allowed into the canister through the vent valve to ensure that the purge flow is maintained when the negative pressure (vacuum) is applied to the canister. The following two monitors run to confirm appropriate EVAP system operation.
1. Key-off monitor
This monitor checks for Evaporative Emission (EVAP) system leaks and canister pump module malfunctions. The monitor starts 5 hours* after the ignition switch is turned OFF. More than 5 hours are required to allow the fuel to cool down to stabilize the Fuel Tank Pressure (FTP), thus making the EVAP system monitor more accurate.
The leak detection pump creates negative pressure (vacuum) in the EVAP system and the pressure is measured. Finally, the ECM monitors for leaks from the EVAP system and malfunctions in both the canister pump module and purge VSV based on the EVAP pressure.
HINT: *: If the engine coolant temperature is not below 35 °C (95 °F) 5 hours after the ignition switch is turned OFF, the monitor check starts 2 hours later. If it is still not below 35 °C (95 °F) 7 hours after the ignition switch is turned OFF, the monitor check starts 2.5 hours later.
2. Purge flow monitor
The purge flow monitor consists of the two monitors. The 1st monitor is conducted every time and the 2nd monitor is conducted if necessary.
- The 1st monitor
While the engine is running and the purge Vacuum Switching Valve (VSV) is ON (open), the ECM monitors the purge flow by measuring the EVAP pressure change. If negative pressure is not created, the ECM begins the 2nd monitor.
- The 2nd monitor
The vent valve is turned OFF (open) and the EVAP pressure is measured. If negative pressure is not created, the ECM interprets this as the purge VSV being stuck closed, illuminates the MIL and sets DTC P0441 (2 trip detection logic).
Atmospheric pressure check: In order to ensure reliable malfunction detection, the variation between the atmospheric pressures, before and after conduction of the purge flow monitor, is measured by the ECM.
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INSPECTION PROCEDURE
NOTE: The intelligent tester is required to conduct the following diagnostic troubleshooting procedure.
HINT:
- Using the intelligent tester monitor results enable the EVAP system to be confirmed.
- Read freeze frame data using the intelligent tester. Freeze frame data records the engine conditions when malfunctions are detected. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air-fuel ratio was lean or rich, and other data from the time the malfunction occurred.
MONITOR DESCRIPTION
Monitor Strategy:
Typical Enabling Conditions (Part 1):
Typical Enabling Conditions (Part 2):
Typical Malfunctions Thresholds:
5 hours* after the ignition switch is turned OFF, the leak detection pump creates negative pressure (vacuum) in the EVAP system. The ECM monitors for leaks and actuator malfunctions based on the EVAP pressure.
HINT: *: If the engine coolant temperature is not below 35 °C (95 °F) 5 hours after the ignition switch is turned OFF, the monitor check starts 2 hours later. If it is still not below 35 °C (95 °F) 7 hours after the ignition switch is turned OFF, the monitor check starts 2.5 hours later.
P2420: Vent valve stuck open (vent)
In operation C, the vent valve turns ON (closes) and the EVAP system pressure is then measured by the ECM, using the canister pressure sensor, to conduct an EVAP leak check. If the pressure does not increase when the vent valve is open, the ECM interprets this as the vent valve being stuck open. The ECM illuminates the MIL and sets the DTC.
MONITOR RESULT
Refer to the CHECKING MONITOR STATUS. Mode 6 Data