P0452

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. The control module supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the FTP decreases, negative pressure or vacuum, high voltage. The FTP sensor signal voltage decreases as the FTP increases, positive pressure, low voltage. This DTC sets when the FTP sensor signal goes below a predetermined value.

CONDITIONS FOR RUNNING THE DTC
The engine is running

CONDITIONS FOR SETTING THE DTC
^ The FTP voltage is less than 0.1 volt
^ All conditions present for greater 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

DTC P0452 - Steps 1-4:

DTC P0452 - Steps 5-13:

The numbers below refer to the step numbers on the diagnostic table.
2. If DTC P1639 sets, the 5-volt reference may be shorted to ground.
5. If the FTP sensor voltage is near 5 volts, the FTP sensor signal and 5-volt reference circuits are OK from the fuel tank harness connector to the control module.