OBD II Fault Code
OBD II P0450
Fault Code Definition
Evaporative Control System Pressure Sensor Malfunction
Symptoms
Check Engine Light will illuminate
In most cases, there are no adverse conditions noticed by the driver
In some cases, there may be a noticeable fuel odor caused by the release of fuel vapors
Common Problems That Trigger the P0450 Code
Defective Fuel Tank Sending Unit
Defective or damaged Fuel Tank
Defective Fuel Tank Pressure Sensor, wiring, or computer
Common Misdiagnoses
Fuel Cap
Evaporative Purge Valve
Evaporative Vent Valve
Polluting Gases Expelled
HCs (Hydrocarbons): Unburned droplets of raw fuel that smell, affect breathing, and contribute to smog
The Basics
The Fuel Tank Pressure Sensor is a device that tracks any positive or negative pressure changes in the Fuel Storage or Evaporative Control (EVAP) system. It constantly relays this pressure information to the Powertrain Control Module (PCM). The Fuel Tank Pressure Sensor is located on top of the Fuel Tank, or on or near the Fuel Pump and Fuel Gauge Module.
Want to Learn More?
The Evaporative Control system Pressure Sensor code sets when the readings of the Pressure Sensor remain at a fixed value and do not change for ten seconds of vehicle operation after a cold start.
P0450 Diagnostic Theory for Shops and Technicians
The Code P0450 indicates that the Evaporative Pressure Sensor output value is not changing during the EVAP Monitor test and/or the operation of the vehicle. This code uses "two trip" logic, which means that the fault condition must be present during two successive cold starts and vehicle operation.
Common Tests for the Evaluating the Fuel Tank Pressure Sensor
Retrieve the code and write down the freeze frame information to be used as a baseline to test and verify any repair.
Pay very close attention to the Fuel Tank Pressure readings by observing its data stream on a scan tool. Does the Fuel Tank Pressure Sensor work properly? If it doesn't, the system will think that no vacuum is being created when, in fact, there is a vacuum being created that the Fuel Tank Pressure Sensor is unable to read. The Fuel Tank Pressure Sensor is the primary feedback sensor that the Powertrain Computer relies on for the leak test data.
Inspect and test the Fuel Pressure Sensor wiring. Verify that there is a 5-volt reference signal from the PCM, a good ground, as well as a good signal return circuit to the PCM.
While observing the data stream change (or lack there of) on a scan tool, test the Pressure Sensor with a Vacuum Gauge while it is connected to the wiring harness.
If all of the above test results are within spec, then the problem may reside in the PCM itself.
