P0451

DTC P0451: Fuel Tank Pressure (FTP) Sensor Performance

Wiring Diagram:

Circuit Description
The control module monitors the Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the Evaporative emission (EVAP) diagnostic test. The control module supplies a 5 volt reference and a low reference circuit to the FTP sensor. If the FTP sensor signal voltage is not within a calibrated value range during a cold engine start, this DTC sets.

Conditions for Setting the DTC
- Engine is running.
- Minimum purge flow fluctuation is greater than 0.3501 g/s.
- FTP sensor voltage fluctuation is less than 0.05 V for 10 times.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will illuminate.
- The ECM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame and Failure Records buffers.
- A history DTC is stored.

Conditions for Clearing the MIL/DTC
- The MIL will turn OFF after four consecutive ignition cycles in which the diagnostic runs without a fault.
- A history DTC will clear after 40 consecutive warm up cycles without a fault.
- The DTC(s) can be cleared using the scan tool.

Diagnostic Aids
Inaccurate readings will occur if resistance measurements are taken on a fuel tank pressure sensor. The fuel tank pressure sensor contains an internal amplifier circuit that requires applied voltage to function properly.

The FTP sensor on the scan tool should be between 2.35 - 2.85 V with the ignition ON and the engine OFF and the fuel cap removed. This represents atmospheric pressure or 0 inches of vacuum.

Step 1-12:

Step 13-14:

Troubleshooting