Faulty EVAP pressure sensor (fuel tank pressure sensor); Damaged, chafed or corroded wiring or connector to the sensor (open circuit, short to earth or short to supply); Blocked, kinked or cracked EVAP vent or vapour lines affecting the pressure reading; Faulty or stuck purge valve or vent valve causing abnormal pressure in the system; Loose, damaged or incorrect fuel filler cap, or a damaged filler neck seal; Fault in the engine control unit's sensor supply or signal input.

P0450

EVAP System Pressure Sensor/Switch A Circuit.

Generic
Powertrain
Generic code
Low severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
50: FaultThe specific fault in that area

What it means

P0450 is the generic code for a fault in the evaporative emission (EVAP) system pressure sensor or switch 'A' circuit. The engine control unit monitors the sensor's signal and sets the code when the reading is implausible, out of range, or does not change as expected during EVAP system tests. The sensor's location and the exact test conditions vary by model and engine.

Symptoms

Engine management warning light on
Failed emissions or MOT-related readiness checks
Fuel smell around the car or fuel tank area
Difficulty refuelling, such as the pump clicking off repeatedly (model dependent)
Other EVAP codes stored alongside, such as leak or purge valve faults
Usually no noticeable change in driveability

Possible causes

Faulty EVAP pressure sensor (fuel tank pressure sensor)likely
Damaged, chafed or corroded wiring or connector to the sensor (open circuit, short to earth or short to supply)likely
Blocked, kinked or cracked EVAP vent or vapour lines affecting the pressure readingpossible
Faulty or stuck purge valve or vent valve causing abnormal pressure in the systempossible
Loose, damaged or incorrect fuel filler cap, or a damaged filler neck sealpossible
Fault in the engine control unit's sensor supply or signal inputrare

How to diagnose

Read all stored and pending codes and note freeze frame data, looking for related EVAP codes
Check the fuel filler cap is fitted, the correct type, undamaged and tightened properly
Visually inspect the sensor, its connector and the wiring for damage, corrosion, water ingress or chafing
Locate the sensor using model-specific information, as its position depends on the vehicle, and check the connector pins for tightness
With the ignition on, check the sensor's reference supply, earth and signal voltages against the manufacturer's specification
View live sensor data with the system at rest and compare it with expected values; check it responds when the purge or vent valve is operated using a bidirectional test
Inspect EVAP hoses, the vent line and the canister area for blockage, kinks, cracks or damage
Test purge and vent valve operation and electrical resistance against specification

How to fix

Repair or replace damaged wiring or connectors in the sensor circuit
Replace the EVAP pressure sensor if its signal is out of range or fails to respond
Replace a faulty or sticking purge valve or vent valve
Clear blockages and replace cracked, kinked or disconnected EVAP lines
Replace a faulty or incorrect fuel filler cap or damaged filler seal
Check for a manufacturer software update only if one is documented for this fault on the specific model

Can I keep driving?

Low severity

The car can normally be driven as usual, as this fault mainly affects the emissions monitoring. Book it in for repair soon, particularly if you can smell fuel, as the EVAP system should be working properly and the fault could lead to a failed emissions test.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.