P0451
DTC P0451
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (Diagnostic System Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (Strategy Based Diagnosis) for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions (Diagnostic Procedure Instructions) provides an overview of each diagnostic category.
DTC Descriptors
DTC P0451
- Fuel Tank Pressure (FTP) Sensor Performance
Diagnostic Fault Information
Typical Scan Tool Data
Circuit/System Description
The FTP sensor is used to detect any unexpected pressure in the EVAP system. The PCM supplies a 5-volt reference, an electrical ground, and a signal return circuit that has a 5-volt bias. The FTP sensor contains a silicon based chip that changes electrical resistance when pressure is applied. The sensor converts the positive or the negative pressure into an electrical signal and sends the signal to the PCM.
Conditions for Running the DTC
Condition 1
* Intake air temperature is between 4-35°C (40-95°F).
* Atmospheric pressure is between 70-110 kPa.
* Battery voltage is greater than 10.5 volts.
* The engine is running.
* DTC P0451 runs once per drive cycle when the above conditions have been met.
Condition 2
* Intake air temperature is between 4-35°C (40-95°F).
* The ignition has been OFF continuously for 5, 7 or 9.5 hours.
* The engine coolant temperature is between 4-35°C (40-95°F).
* Atmospheric pressure is between 70-110 kPa.
* Battery voltage is greater than 10.5 volts.
* DTC P0451 runs once per drive cycle when the above conditions have been met.
Conditions for Setting the DTC
Condition 1
The FTP sensor output voltage rapidly shifts from inside to outside a specified range 10 times within 10 seconds.
Condition 2
The FTP sensor signal voltage is fixed during the FTP sensor test portion of the engine OFF EVAP diagnostic.
Action Taken When the DTC Sets
DTC P0451 is a Type B DTC.
Conditions for Clearing the DTC
DTC P0451 is a Type B DTC.
Reference Information
Schematic Reference
Engine Controls Schematics ([1][2]Electrical Diagrams)
Connector End View Reference
Component Connector End Views (Connector Views)
Description and Operation
Evaporative Emission Control System Description (Evaporative Emission Control System Description)
Electrical Information Reference
* Circuit Testing (Circuit Testing)
* Connector Repairs (Connector Repairs)
* Testing for Intermittent Conditions and Poor Connections (Testing for Intermittent Conditions and Poor Connections)
* Wiring Repairs (Wiring Repairs)
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions (Powertrain Diagnostic Trouble Code (DTC) Type Definitions)
Scan Tool Reference
Control Module References (Programming and Relearning) for scan tool information
Circuit/System Verification
1. Ignition OFF, remove the fuel tank filler cap.
Note: The FTP sensor reading will vary slightly with atmospheric pressure. The values indicated are for pressures at sea level.
2. Ignition ON, observe the scan tool FTP sensor parameter. The reading should be between 3.5-3.8 V.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
Circuit/System Testing
1. Ignition OFF, remove the fuel tank filler cap.
Note: The FTP sensor reading will vary slightly with atmospheric pressure. The values indicated are for pressures at sea level.
2. Ignition ON, observe the scan tool FTP sensor parameter. The reading should be between 3.5-3.8 V.
• If greater than the specified range, disconnect the fuel tank ORVR vent line that connects to the evaporative emission (EVAP) canister. If the scan tool FTP sensor parameter is still greater than 3.5-3.8 V, repair the trapped vapor pressure in the fuel tank.
• If less than the specified range, test for high resistance in the FTP sensor signal circuit terminal 3.
3. If all circuits test normal, replace the FTP sensor.
Repair Instructions
Perform the Diagnostic Repair Verification (Verification Tests) after completing the diagnostic procedure.
* Evaporative Emission System Vacuum Leak Pump Replacement (Service and Repair)
* Control Module References (Programming and Relearning) for control module replacement, setup, and programming