Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P0451: Fuel Tank Pressure (FTP) Sensor PerformanceDiagnostic Fault Information
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
5-Volt Reference | * | -- | P0120, P0122, P0450, P0453 | ** | -- |
FTP Sensor Signal | P0452 | P0451 | P0453 | P0453** | P0451 |
Low Reference | -- | P0451 | P0110, P0113, P0115, P0118, P0120, P0123, P0220, P0223, P0450, P0453 | -- | -- |
*Engine cranks but won't start **Internal PCM or FTP sensor damage may occur if the circuit is shorted to B+ | |||||
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: The engine coolant temperature is greater than 70°C (158°F) and the ignition is ON with the engine is OFF. Parameter Normal Range: FTP Sensor 3.5-3.8 volts | |||
5-Volt Reference | * | 5.0 volts | ** |
FTP Sensor 1 Signal | 0.1 volts | 5.0 volts | 5.0 volts |
Low Reference | -- | 5.0 volts | -- |
*No scan tool communication with control module **Internal PCM or FTP sensor damage may occur if the circuit is shorted to B+ | |||
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.
Fuel Tank Vapor Space | FTP mmHg | FTP Signal Voltage |
|---|---|---|
Pressure | Positive Value | High |
No Pressure | Near Zero | 3.0-3.6V |
Vacuum | Negative Value | Low |
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). |
| • | Atmospheric pressure is between 70-110 kPa. |
| • | Battery voltage is greater than 10.5 volts. |
| • | The ignition has been OFF continuously for greater than 5 hours. |
| • | 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 appears 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
Connector End View Reference
Description and Operation
Evaporative Emission Control System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition OFF, remove the fuel tank filler cap.
- Ignition ON, observe that the scan tool FTP sensor parameter is between 3.5-3.8 volts.
- 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.
Important: The FTP sensor reading will vary slightly with atmospheric pressure. The values indicated are for pressures at sea level.
Circuit/System Testing
- Ignition OFF, remove the fuel tank filler cap.
- Ignition ON, observe the scan tool FTP sensor parameter is between 3.5-3.8 volts.
- If all circuits test normal, replace the FTP sensor located in the EVAP vacuum leak pump assembly.
Important: The FTP sensor reading will vary slightly with atmospheric pressure. The values indicated are for pressures at sea level.
| ⇒ | 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 volts, 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. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for control module replacement, setup, and programming |
