Technical Description of OBD-II Trouble Code
Malfunction in the Pressure Sensor of the Evaporative Emission Control System
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that applies to OBD-II equipped vehicles such as Dodge, Ram, Ford, GMC, Chevrolet, VW, Audi, Toyota, etc. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
A stored code P0450 indicates that the powertrain control module (PCM) has detected a malfunction in the pressure sensor circuit of the evaporative emissions (EVAP) system.
The EVAP system is designed to capture fuel vapors from the fuel tank before they escape into the atmosphere. It utilizes a vented reservoir, commonly known as a canister, to store excessive vapors until the engine is being operated under the appropriate conditions to burn them thoroughly.
Fuel storage tank vapors are discharged through the pressure relief valve to the canister via a network of metal tubes and rubber hoses. The pressure developed when fuel is stored acts as the propellant, causing the vapors to vent through the tubes and eventually into the canister. The canister contains a charcoal element that absorbs fuel vapors and holds them for release at the appropriate time.
The EVAP system consists of various components, including the charcoal canister, EVAP pressure sensor, purge valve/solenoid, vent control valve/solenoid, and a complex system of metal tubes and rubber hoses stretching from the fuel tank to the engine compartment.
The EVAP system utilizes engine vacuum to draw fuel vapors into the intake manifold, where they can be burned instead of being released into the atmosphere. The PCM controls the purge control valve/solenoid, which regulates intake vacuum to the EVAP canister, allowing fuel vapors to be drawn into the engine when conditions are ideal for efficient fuel vapor burning.
The EVAP pressure sensor enables the PCM to monitor the pressure in the EVAP system. It is typically located in the fuel tank and integrated into the fuel pump/fuel level sending unit housing. If the EVAP and/or fuel tank pressure deviate from the predetermined range over a set period of time and under certain circumstances, a code P0450 will be stored, and the malfunction indicator lamp (MIL) may illuminate.
Other related evaporative emission trouble codes include P0451, P0452, P0453, P0454, P0455, P0456, P0457, P0458, and P0459.
Code Severity & Symptoms
The code P0450 is associated with emissions regulation and does not significantly affect engine drivability. It should not be considered severe.
Symptoms of this code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
To diagnose a code P0450, you will need a diagnostic scanner, a digital volt/ohmmeter, a reliable vehicle information source (All Data DIY), and possibly a smoke machine.
Start by visually inspecting the EVAP system hoses and lines, paying attention to those routed near sharp edges or hot exhaust components. Remove the fuel cap and inspect the seal, then properly screw it back on.
Connect the scanner to the vehicle diagnostic port and retrieve all stored codes and freeze frame data. Make a note of this information as it may be helpful if the code is intermittent. Clear the codes and test drive the vehicle until it either enters OBD-II readiness mode or the code is reset. EVAP codes usually require multiple drive cycles before they are reset.
Use the diagnostic stream of the scanner to observe EVAP pressure sensor data. If the system pressure is within the manufacturer’s recommended specifications, suspect that tightening or replacing the fuel cap has resolved the issue.
Since this is specifically an EVAP pressure sensor code, it is advisable to test the EVAP pressure sensor before performing a smoke test. The EVAP pressure sensor is usually located at the top of the fuel storage tank. Gain access to the sensor and follow the manufacturer’s recommendations for testing. Replace the sensor if it fails to comply with specifications.
If the EVAP pressure sensor appears to be functioning properly, unplug all related controllers and test individual circuits with the DVOM. Replace any open or shorted circuits as necessary.
Additional diagnostic notes:
