P0452

Circuit Description

The EVAP Fuel Tank Pressure sensor is a sensor that changes resistance based upon fuel tank pressure (or vacuum). A vacuum is considered negative pressure.

The PCM provides a 5 volt reference and ground. The EVAP Fuel Tank Pressure sensor signal varies between ground and 5 volts as fuel tank pressure varies. As pressure decreases (negative pressure, or vacuum), voltage increases. As pressure increases, voltage decreases (positive pressure, low voltage). The PCM uses the EVAP Fuel Tank Pressure sensor values as an indicator of EVAP system efficiency. If the EVAP Fuel Tank Pressure sensor signal goes low such as when the signal line is shorted to ground or the EVAP Fuel Tank Pressure sensor is shorted internally, this DTC will set.

Conditions for Running the DTC

^ DTC P0601 is not set.
^ Fuel level at engine start up is the same or less than 85% full.
^ The Intake Air Temperature (TAT) at engine start up is between 2°C and 60°C.

Conditions for Setting the DTC

The EVAP Fuel Tank Pressure sensor reading has been 0.10 volts or lower.

Action Taken When the DTC Sets

PCM disables Evaporative Emission (EVAP) control solenoid.

^ The PCM will illuminate the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
^ The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records.

Conditions for Clearing the MIL/DTC

^ The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.
^ A Last Test Failed (current) DTC will clear when the diagnostic runs and does not fail.
^ A History DTC will clear after forty consecutive warm-up cycles with no failures of any emission related diagnostic test.
^ Use a scan tool to clear DTCs.
^ Interrupting PCM battery voltage may or may not clear DTCs. This practice is not recommended.

Diagnostic Aids

The EVAP Fuel Tank Pressure Sensor monitors a range from 7.5 in. H2O of pressure to -17.5 in. H2O of pressure (vacuum).

The vacuum and pressure in the EVAP system is measured in inches of H2O (water). Most gauges measure vacuum in inches of Hg (mercury) and pressure in psi (pounds per square inch). The following shows how the values compare:

in.H2O in.Hg psi

1 in. H2O 0.07 in. hg 0.0361 psi.
5 in. H2O 0.36 in. hg 0.180 psi.
10 in. H2O 0.73 in. hg 0.361 psi.
15 in. H2O 1.10 in. hg 0.541 psi.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

2. If the EVAP Fuel Tank Pressure sensor or circuitry are open or grounded, the sensor parameter will read 0.10 volts or less.
If fault is not present monitor the scan too] display for this sensor while manipulating the vehicle's electrical harness. A change in sensor output while manipulating the harness may indicate a circuit fault.
3. Checking if circuitry from sensor to PCM is able to respond to a 5 volt signal on the sensor input. A reading of 4.80 volts or more means wiring and PCM are OK.
17. Disconnect the suspect sensor and re-measure the resistance between the 5 volt reference and sensor ground circuits. If infinite resistance is measured the sensor is shorted.