P0453

CIRCUIT DESCRIPTION
The control module monitors the fuel tank pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced evaporative emission (EVAP) diagnostic test. The control module supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the FTP or vacuum decreases. This is also referred to as negative pressure or vacuum, and high voltage. The FTP sensor signal voltage decreases as the FTP increases. This is also referred to as positive pressure, and low voltage. When the FTP sensor signal voltage goes above a predetermined value, DTC P0453 will set.

CONDITIONS FOR RUNNING THE DTC
The engine is running.

CONDITIONS FOR SETTING THE DTC
^ The FTP sensor voltage is more than 4,9 volts.
^ All conditions exists for more than 5 seconds.

ACTION TAKEN WHEN THE DTC SETS
^ The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
^ The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

CONDITIONS FOR CLEARING THE MIL/DTC
^ The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
^ A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
^ A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
^ Clear the MIL and the DTC with a scan tool.

TEST DESCRIPTION

Steps 1-8:

Steps 6-14:

The number below refers to the step number on the diagnostic table.
2. If DTC P1639 set, the 5-volt reference circuit may be shorted to a voltage.