P0451

DTC P0451 or P0454

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. Initial Inspection and Diagnostic Overview
* Review Strategy Based Diagnosis for an overview of the diagnostic approach.
* Diagnostic Procedure Instructions provide an overview of each diagnostic category.

DTC Descriptors

DTC P0451
- Fuel Tank Pressure (FTP) Sensor Performance

DTC P0454
- Fuel Tank Pressure (FTP) Sensor Intermittent

Typical Scan Tool Data






Circuit/System Description

The evaporative emission (EVAP) system is used to store fuel vapors in order to reduce the amount of fuel vapors into the atmosphere. The fuel tank pressure (FTP) sensor is only used for EVAP system diagnostics. The FTP sensor is a transducer that varies resistance according to changes in the 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 test.




The table illustrates the relationship between FTP sensor signal voltage and the EVAP system pressure/vacuum.


Conditions for Running the DTC

* The engine is running.
* DTCs P0451 and P0454 run once an ignition cycle when the above condition is met.

Conditions for Setting the DTC

P0451

The ECM detects the FTP sensor voltage is less than 0.58 volt within 13 seconds after start up.

P0454

The ECM detects an abrupt change in the FTP sensor voltage.

Action Taken When the DTC Sets

DTC P0451 and P0454 are Type B DTCs.

Conditions for Clearing the MIL/DTC

DTC P0451 and P0454 are Type B DTCs.

Diagnostic Aids

If a shared 5-volt reference circuit is shorted to ground or shorted to a voltage, other 5-volt reference circuits may be affected.

Circuit/System Testing

1. If DTC P0454 is set Inspect for an intermittent and for a poor connection at the FTP sensor and the engine control module (ECM).
2. 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.

Important: The EVAP vent solenoid valve will not remain closed when commanded ON with positive pressure applied to the EVAP system.

3. Disconnect the EVAP vent line from the vent solenoid, and seal it, using the correct plug from the J 41413-300.
4. Pressurize the EVAP system with nitrogen to 5 inches H20. 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 H20 of the pressure/vacuum gage.

• If the FTP sensor parameter is not within 1 inch H20 of the pressure/vacuum gage, replace the FTP sensor.

5. Command the purge solenoid valve OPEN with a scan tool.

• If the FTP sensor parameter is not 0 inch H20, replace the FTP sensor.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure. Verification Tests

* Fuel Tank Pressure Sensor Replacement
* Programming and Relearning for ECM setup, and programming Programming and Relearning