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. The control module supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases when the FTP decreases. Negative pressure or vacuum indicates high voltage. The FTP sensor signal voltage decreases when the FTP increases. Positive pressure indicates 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 sensor voltage is less than 0.1 volts
^ All conditions are present 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 1-4:

Steps 5-14:

The numbers below refer to the step numbers on the diagnostic table.
5. This step tests for the proper operation of the circuit in the high voltage range.
6. The 5-volt reference circuit for the FTP sensor is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.
7. The FTP sensor signal circuit is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.