P2421 - EVAPORATIVE EMISSION SYSTEM VENT VALVE STUCK OPEN

The EVAP (Evaporative Emission Control) system retains fuel vapors to prevent them from escaping into the atmosphere. This is done until the PCM determines the conditions and time at which the vapors can be purged and engine damage is prevented.

In this system are the fuel filler cap, fuel tank, charcoal canister, valves, vacuum lines, and pressure sensors. The vapors are stored in the charcoal canister, which is connected to the vent valve, which is usually closed, in order to prevent the vapors from escaping.

The P2421 OBDII fault code setting indicates that the vent valve experienced a lockout condition in the open position.

• Check Engine light comes on.
• Other codes associated with the evaporative emissions system are set.

The P2421 OBD2 diagnostic code is set by one or more of the following:

• The fuel cap may not be tightened properly.
• The vacuum hoses or lines could have blockages or be improperly tightened.
• The EVAP system wires or connectors may have deficiencies causing the malfunction.
• The vent valve may have been damaged.
• The vent valve solenoid could have defects.
• Possibly the purge control solenoid is defective.

To troubleshoot the DTC P2421 OBDII code you must do the following:

• Check the fuel cap to make sure it is properly tightened.
• Check the wires associated with the Evaporative Emission Control System for defects caused by high temperatures. Repair or replace as required.
• Check the EVAP system connectors for pin damage and that they are properly connected. If inconsistencies are detected, make adjustments accordingly.
• Inspect the EVAP system vacuum lines and hoses for leaks. Repair it as required.
• Replace the EVAP system vent valve.