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 PerformanceDTC P0454: Fuel Tank Pressure (FTP) Sensor Intermittent
Diagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
5-Volt Reference | P0452, P0532, P0641 | P0452 | P0641 | -- |
FTP Sensor Signal | P0452 | P0452 | P0453 | -- |
Low Reference | -- | P0463 | -- | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Operating Conditions: Engine operating in Closed Loop at idle Parameter Normal Range: 0.2-4.8 V | |||
5-Volt Reference Voltage | 0 V | 0 V | 2.5 V |
FTP Sensor Signal | 0 V | 0 V | 5.0 V |
Low Reference | -- | 4.5 V | -- |
Circuit/System Description
The evaporative emission (EVAP) system stores fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in fuel tank pressure. The engine control module (ECM) monitors the FTP sensor signal in order to detect vacuum decay and excess vacuum during the EVAP system diagnostic tests.
The following table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.
FTP Sensor Signal Voltage | Fuel Tank Pressure |
|---|---|
High, Approximately 1.5 Volts or More | Negative Pressure/Vacuum |
Low, Approximately 1.5 Volts or Less | Positive Pressure |
Conditions for Running the DTC
P0451
| • | This diagnostic runs when the engine-off natural vacuum small leak test, P0442, is in progress. |
| • | This diagnostic can be tested 2 times during the engine-off period. |
P0454
| • | This diagnostic runs when the engine-off natural vacuum small leak test, P0442, is in progress. |
| • | This diagnostic can be tested 1 time during the engine-off period. |
| • | The ECM does not detect a refueling event. |
Conditions for Setting the DTC
P0451
DTC P0451 will set if the controller is unable to re-zero the FTP sensor voltage within a calibrated range. The length of the test can be up to 10 minutes.
P0454
The ECM detects an abrupt change in the FTP sensor voltage, other than a refueling event. The length of the test can be up to 10 minutes.
Action Taken When the DTC Sets
DTC P0451 and P0454 are Type A DTCs.
Conditions for Clearing the MIL/DTC
DTC P0451 and P0454 are Type A DTCs.
Diagnostic Aids
| • | A restriction in the EVAP canister or vent lines could prevent fuel vapor pressure from decreasing fast enough. If the pressure does not decrease fast enough, the re-zero procedure may not complete successfully, which could cause DTC P0451 to set. |
| • | Verify that the reference port on the FTP sensor is not restricted. |
| • | A resistance in the circuits of the FTP sensor may cause DTC P0451 to set. |
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
Special Tools
| • | J 41413-200 Evaporative Emissions System Tester (EEST) |
| • | GE-41415-50 Fuel Tank Cap Adapter |
| • | J 41413-300 EVAP Cap and Plug Kit |
Circuit/System Testing
- If DTC P0454 is set Inspect for an intermittent and for a poor connection at the FTP sensor and the engine control module (ECM).
- Remove the fuel fill cap. Connect the GE-41415-50 to the fuel tank filler neck. Connect the J 41413-200 to the GE-41415-50 .
- Pressurize the EVAP system with nitrogen to 5 inches H2O. Compare the Fuel Tank Pressure Sensor parameter with a scan tool to the J 41413-200 pressure/vacuum gage. The scan tool FTP sensor parameter should be within 1 inch H2O of the pressure/vacuum gage.
- Command the EVAP purge solenoid valve OPEN with a scan tool. Verify the scan tool FTP senor parameter decreases quickly to 0 inch H2O.
| ⇒ | If not within the specified range, replace the FTP sensor. |
| ⇒ | If the pressure does not decrease quickly, inspect the EVAP vent system for a restriction. If the EVAP vent system tests normal replace the FTP sensor. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for ECM replacement, setup, and programming |
