DTC Descriptor
DTC P0451: Fuel Tank Pressure (FTP) Sensor PerformanceDiagnostic Fault Information
Important: Always perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
Circuit | Short to Ground | High Resistance | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|---|
FTP Sensor Low Reference | -- | P0446, P0451 | P0446 | -- | P0451 |
FTP Sensor Signal | P0452 | -- | P0452 | P0453 | P0451, P0454 |
FTP Sensor 5-Volt Reference | P0452, P0530, P0641 | P0451 | P0446, P0453 | P0453, P0530, P0641 | -- |
Typical Scan Tool Data
Circuit¹ | Normal Range | Short to Ground | Open | Short to Voltage |
|---|---|---|---|---|
FTP Sensor Low Reference | -- | 1.5 V | 4.5 V | -- |
FTP Sensor Signal | 1.5 V | 0 V | 0 V | 5 V |
FTP Sensor 5-Volt Reference | 0 V | 0 V | 5 V | |
¹ With EVAP system vented to atmosphere | ||||
Circuit/System Description
The fuel tank pressure (FTP) sensor measures air pressure or vacuum in the evaporative emission (EVAP) system. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal voltage varies depending on EVAP system pressure or vacuum. The controller also uses this FTP signal to determine atmospheric pressure for use in the engine-off small leak test, DTC P0442. Before using this signal as an atmospheric reference it must first be re-zeroed.
Conditions for Running the DTC
| • | DTC P0451 runs only when the engine-off natural vacuum small leak test, DTC P0442, executes. |
| • | The number of times this test runs can range from 0-2 per engine-off period. The length of the test can be up to 10 minutes. |
Conditions for Setting the DTC
This DTC will set if the controller is unable to re-zero the FTP sensor voltage within a calibrated range during the engine-off small leak test, DTC P0442.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/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. |
Diagnostic Aids
| • | A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from bleeding off fast enough. If the vent system cannot bleed off pressure fast enough, the re-zero procedure may not complete successfully, which could cause this code to set. By using the purge solenoid command on a scan tool, vacuum can be applied to the system instead of pressure. With the EVAP canister vent solenoid valve open and the EVAP canister purge solenoid valve commanded to 100 percent, the vacuum should not increase to more than 9 inches H2O. |
| • | Ensure that the reference port on the FTP sensor is unobstructed. |
Reference Information
Schematic Reference
Connector End View Reference
Electrical Information Reference
Scan Tool Reference
Special Tools Required
J 41413-200 Evaporative Emission System Tester (EEST)
Circuit/System Verification
- If DTCs P0452, P0453, or P0641 are set, repair those first.
- With a scan tool, command the EVAP canister vent solenoid valve closed.
- Command the purge solenoid to 20 percent.
- Observe the FTP sensor voltage parameter as the vacuum increased to the abort limit.
- The voltage should scale smoothly.
Circuit/System Testing
- Start the engine with the J 41413-200 connected to the fuel filler neck.
- Allow the engine to idle.
- Use the Purge/Seal function to seal the system with a scan tool.
- Command the EVAP canister purge solenoid valve to 20 percent.
- Observe the vacuum/pressure gage on the J 41413-200 and the FTP parameter on the scan tool.
- Allow the vacuum to increase on the gage of the J 41413-200 until it reaches approximately 16 inches H2O, or until the vacuum reached the abort limit on the scan tool.
- Use the Purge/Seal function to seal the system with a scan tool.
- If the difference between the FTP parameter on a scan tool and the vacuum/pressure gage on the J 41413-200 is more than 1 inch H2O, replace the FTP sensor.
- If the Fuel Tank Pressure Sensor parameter on a scan tool display is less than 3.2 volts, replace the FTP sensor.
Important: Refer to the J 41413-200 operation manual for detailed instructions.
Repair Instructions
Important: Always perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
