DTC Advanced Diagnostics: P0451
DTC P0451:Evaporative Emission (EVAP) Leak Check Module Pressure Sensor Range/Perfomance

General Description
The powertrain control module (PCM) monitors the leak detction pressure sensor output voltage. The leak detction pressure sensor output voltage rises as the fuel tank pressure increases. Conversely, the leak detction pressure sensor output voltage drops as the fuel tank pressure decreases. Rapid changes in the leak detction pressure sensor output voltage due to electrical noise or an intermittent open during the EVAP leak detection may cause incorrect leak detection, so abnormal output is monitored. If the leak detction pressure sensor output voltage change occurs for specified ratio within a set time, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type
Execution
Once per driving cycle
Sequence
None
Duration
31 seconds or more
DTC Type
Two drive cycles, MIL on

Enable Conditions
Condition
Minimum
Maximum
Elapsed time after starting the engine
10 seconds
–
Engine coolant temperature [ECT SENSOR 1]
131 °F (55 °C)
–
12 volt battery voltage [BATTERY]
10.5 V
–
EVAP canister purge valve duty [EVAP PC DUTY]
Other than 0 %
Fuel feedback
During deceleration
Other
Other than purge-cut operation
[ ]: HDS Parameter

Malfunction Threshold
The leak detction pressure sensor output voltage change occurs for specified ratio within a set time.

Possible Cause
NOTE: The causes shown may not be a complete list of all potential problems, and it is possible that there may be other causes.
Leak detction pressure sensor failure

Confirmation Procedure
Operating Condition

1.
Start the engine and let it idle until the radiator fan comes on.
2.
Drive the vehicle at a steady speed 35 mph (56 km/h) for at least 10 seconds.
3.
Decelerate with the throttle valve fully closed.
4.
Repeat Driving Pattern steps 2 through 3, three times.
Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.
With the HDS
None.

Diagnosis Details
Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC, the freeze data, and the on-board snapshot are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, the freeze data, and the on-board snapshot can be cleared with the scan tool Clear command or by disconnecting the 12 volt battery.