P0450 OBD-II: Evaporative Emission System Pressure Sensor/Switch

OBD II Fault Code

• OBD II P0452

OBD-II Code P0450 is defined as a Evaporative Control System Pressure Sensor Low Input

The Code P0452 indicates that the Evaporative Pressure Sensor is indicating pressure change values that are below specification, during the EVAP Monitor test and/or the operation of the vehicle.

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The evaporative control (EVAP) system captures any raw fuel evaporating from the fuel storage system (e.g. the fuel tank, filler neck, and fuel cap). Under precise operating conditions—dictated by engine temperature, speed, and load—the EVAP system stores and purges these captured fuel vapors back into the combustion process.

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.

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 P0452 Code

• Defective Fuel Tank Sending Unit
• Defective or damaged Fuel Tank
• Defective Fuel Tank Pressure Sensor, wiring, or computer
• Defective Carbon Canister
• Defective Canister Vent Valve - in some cases

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.

P0452 Diagnostic Theory for Shops and Technicians

The Evaporative Control System Pressure Sensor Low Input code sets when the readings of the Pressure Sensor are below specification for ten seconds of vehicle operation after a cold start. 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.