The ECM monitors the fuel tank internal pressure using the vapor pressure sensor. The ECM supplies the sensor with a regulated 5 V reference voltage, and the sensor provides the ECM with a signal voltage of between 0.5 V and 4.5 V as feedback, depending on the pressure level in the fuel tank.
When the pressure in the fuel tank is low, the output voltage of the vapor pressure sensor is low. When it is high, the output voltage is high.
- The ECM sets DTC P0451, if either one of the following conditions applies: The ECM checks for noise in the sensor by monitoring the fuel tank internal pressure when the vehicle is stationary. When the vapor pressure sensor is functioning normally, it indicates a small variation in pressure. If the indicated pressure variation deviates from the predetermined level, the ECM illuminates the MIL and sets the DTC.
- The ECM checks for a stuck sensor by monitoring the fuel tank internal pressure for an extended time period. If the indicated pressure value does not vary over the time period, the ECM interprets this as a malfunction in the sensor, and illuminates the MIL and sets the DTC.