Toyota Celica 2005 Repair Manual page 744

DTC P0451
DTC P0452
DTC P0453
MONITOR DESCRIPTION
DTC "P0451, P0452 or P0453" is recorded by the ECM when the vapor pressure sensor malfunctions.
P0451
The ECM monitors pressure in the fuel tank using the vapor pressure sensor. The ECM supplies the sensor
with a regulated 5 V reference voltage and the sensor returns a signal voltage between 0.5 V and 4.5 V ac-
cording to 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.
For this DTC P0451, the ECM checks for a "noisy" sensor or a "stuck" sensor.
The ECM checks for a "noisy" sensor by monitoring the fuel tank pressures when the vehicle is stationary
and there should be little variation in the tank pressure. If the indicated pressure value exceeds specified
limits, the ECM will illuminate the MIL and a DTC will be set.
The ECM checks for a "stuck" sensor by monitoring the fuel tank pressure for an extended time period. If
the indicated pressure value does not change over this period, the ECM will conclude that the fuel tank pres-
sure sensor is malfunctioning. The ECM will illuminate the MIL and a DTC will be set.
P0452 and P0453
The ECM monitors pressure in the fuel tank using the vapor pressure sensor. The ECM supplies the sensor
with a regulated 5 V reference voltage and the sensor returns a signal voltage between 0.5 V and 4.5 V ac-
cording to the pressure level in the fuel tank.
If the output voltage of the vapor pressure sensor is out of normal range, the ECM will determine that there
is a malfunction in the sensor or sensor circuit.
When pressure indicated by the vapor pressure sensor goes below −3.999 kPa (−30 mmHg, −1.18 in.Hg)
or above 1.999 kPa (15 mmHg, 0.59 in.Hg), the ECM interprets this as a malfunction in the vapor pressure
sensor. The ECM will turn on the MIL and a DTC will be set.
2005 CELICA (RM1131U)
DIAGNOSTICS − ENGINE (2ZZ−GE)
Evaporative Emission Control System Pres-
sure Sensor/Switch Range/Performance
Evaporative Emission Control System Pres-
sure Sensor/Switch Low Input
Evaporative Emission Control System Pres-
sure Sensor/Switch High Input
743
DI−545
DI1K0−18