Failed fuel tank pressure sensor (most common cause on older Subaru models); Damaged or corroded wiring harness at the fuel tank pressure sensor connector; Open or shorted circuit between the pressure sensor and the engine control module; Faulty evap canister vent valve or its electrical connector; Loose or corroded ground connection for the evap system; Failed engine control module (rare but possible after other causes are ruled out)

DTC codes / Subaru codes / P1440

P1440 · SubaruFuel Tank Pressure Control System Low Input

Q: What does code P1440 mean?

Fuel Tank Pressure Control System Low Input. P1440 on a Subaru means the engine control module has detected a low electrical input from the fuel tank pressure control system, which monitors the pressure sensor and vent valve circuit used for evaporative emissions testing. The computer expects a voltage signal within a specific range and sees it drop below the minimum threshold, indicating a short to ground, an open circuit, or a failed sensor.

P1440 on a Subaru means the engine control module has detected a low electrical input from the fuel tank pressure control system, which monitors the pressure sensor and vent valve circuit used for evaporative emissions testing. The computer expects a voltage signal within a specific range and sees it drop below the minimum threshold, indicating a short to ground, an open circuit, or a failed sensor.

SystemPowertrain

Code typeSubaru specific

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Illumination of the check engine light, often with no other noticeable symptoms
A slight fuel odor around the rear of the vehicle if the system is stuck open
Difficulty refueling or a fuel filler nozzle that clicks off repeatedly
Rough idle or hesitation in rare cases when the purge flow is affected
Failed emissions inspection due to the stored code
Intermittent warning light that may clear and reset after key cycles

Common causes, most likely first

Failed fuel tank pressure sensor (most common cause on older Subaru models)
Damaged or corroded wiring harness at the fuel tank pressure sensor connector
Open or shorted circuit between the pressure sensor and the engine control module
Faulty evap canister vent valve or its electrical connector
Loose or corroded ground connection for the evap system
Failed engine control module (rare but possible after other causes are ruled out)

How to diagnose and fix it

Connect a scan tool and record freeze-frame data to confirm the code and check for related evap codes
Visually inspect the fuel tank pressure sensor connector and wiring for corrosion, chafing, or loose pins
Measure reference voltage and ground at the pressure sensor connector with the key on
Test the sensor signal wire for continuity and shorts to ground using a multimeter
Check the evap canister vent valve for proper resistance and operation
Replace the fuel tank pressure sensor if electrical tests confirm it is faulty
Clear the code and perform a drive cycle to verify the repair and ensure the monitor completes

What Subaru techs check before replacing the sensor

A low input code often results from a corroded connector pin at the fuel tank pressure sensor rather than a failed sensor itself, especially on older Subaru models exposed to road salt.
The fuel tank pressure sensor on many Subarus is integrated into the evap canister assembly, so technicians should verify the part before ordering a replacement.
A stuck-open evap vent valve can cause the pressure sensor to read low, setting P1440 even when the sensor is good.
Intermittent P1440 codes can be caused by a wiring harness that rubs against the fuel tank shield, so a wiggle test while monitoring live data is essential.
Do not overlook the ground connection for the evap system, as a poor ground can mimic a failed sensor and lead to unnecessary parts replacement.

Can I keep driving with P1440?

The vehicle is safe to drive with P1440 because it only affects the evaporative emissions system and does not impact engine performance or safety. Avoid topping off the fuel tank excessively and have the code diagnosed soon to prevent a small evap leak from worsening.

Tools that help

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Guidance is general and written for Subaru vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.