What does it mean?
The OBDII system on 1996 and newer vehicles is equipped with an evaporative emissions monitor that performs diagnostic self-checks to detect fuel vapor leaks. If a leak is detected, then a code is set in the engine control module and the check engine light is illuminated. The component that reads the fuel vapor pressure is the evaporative emission control system pressure sensor, also referred to as the fuel tank pressure sensor.
The evaporative emission (EVAP) control system pressure sensor is used for onboard diagnosis of the EVAP system itself to check for leaks and does not initiate or control changes to the EVAP purge or vent valve operations. It detects and measures pressure in the purge line of the EVAP system. The pressure sensor’s output voltage increases as the pressure in the purge line increases, and the sensor voltage output is monitored by the engine control module (ECM).
The EVAP system pressure sensor is located at the EVAP canister. It can be mounted directly on the canister or it may be connected to the EVAP canister by a section of hose. EVAP control system pressure sensor. The EVAP control system pressure sensor converts pressure to a voltage reading. The sensor voltage is then communicated to the ECM via a signal wire connected to the sensor. There are three wires for the EVAP pressure sensor: a ground, a 5v reference signal, and the sensor signal wire.
The EVAP pressure sensor is only monitored under certain conditions which can make it tricky to diagnose. Voltage is monitored by the ECM only once the vehicle speed sensor has recorded a trip of one minute at a minimum speed of 10 miles per hour. The ECM only monitors the EVAP control system pressure sensor when the fuel tank level is between 25 and 75 percent.
The code P0450 is set when the ECM reads a voltage signal lower than 0.5v or higher than 4.8v from the EVAP control system pressure sensor for more than 500 milliseconds, or half a second.