Open circuit in the purge valve control wire, commonly at the connector or where the harness flexes near the intake manifold; Failed purge valve solenoid with an open coil winding, which leaves the control line floating high; Corroded or backed-out terminal in the purge valve connector, creating a high-resistance path that the DME reads as high signal; Short to battery voltage on the control wire, often from chafing against a hot or sharp engine component; Failed driver inside the DME, though this is rare and should only be suspected after all wiring and valve checks pass; Water intrusion into the connector or valve body causing intermittent high-signal readings

DTC codes / BMW codes / P1440

P1440 · BMWPurge Control Valve Control Circuit Signal High

Q: What does code P1440 mean?

Purge Control Valve Control Circuit Signal High. P1440 on a BMW means the digital motor electronics (DME) has detected a high-voltage signal on the control circuit for the fuel tank breather (purge) valve, indicating an open circuit, short to voltage, or a failed valve coil. The DME commands the valve to open and close to meter fuel vapor into the intake, and it monitors the circuit for expected voltage behavior. A high signal means the circuit is not pulling the voltage down as expected when the valve is commanded on.

P1440 on a BMW means the digital motor electronics (DME) has detected a high-voltage signal on the control circuit for the fuel tank breather (purge) valve, indicating an open circuit, short to voltage, or a failed valve coil. The DME commands the valve to open and close to meter fuel vapor into the intake, and it monitors the circuit for expected voltage behavior. A high signal means the circuit is not pulling the voltage down as expected when the valve is commanded on.

SystemPowertrain

Code typeBMW specific

SeverityLow

Fix difficultyIntermediate

AreaAuxiliary emission controls

Symptoms you may notice

Often no symptoms besides the warning light, especially if the valve is stuck closed and the tank can still vent through the carbon canister
A faint fuel vapor smell around the rear of the car or in the engine bay after parking
Slightly rough idle or a stumble just after refueling, when purge flow is highest
Intermittent check engine light that clears and returns with temperature or vibration changes
Failed emissions inspection due to the stored fault and incomplete evaporative monitor

Common causes, most likely first

Open circuit in the purge valve control wire, commonly at the connector or where the harness flexes near the intake manifold
Failed purge valve solenoid with an open coil winding, which leaves the control line floating high
Corroded or backed-out terminal in the purge valve connector, creating a high-resistance path that the DME reads as high signal
Short to battery voltage on the control wire, often from chafing against a hot or sharp engine component
Failed driver inside the DME, though this is rare and should only be suspected after all wiring and valve checks pass
Water intrusion into the connector or valve body causing intermittent high-signal readings

How to diagnose and fix it

Clear the fault and road-test with a scan tool to confirm P1440 returns and to check for related evaporative codes
Inspect the purge valve connector and harness for corrosion, chafing, or a loose terminal, repairing as needed
Measure the purge valve coil resistance with a multimeter and compare to BMW specifications for the engine, replacing the valve if open or out of range
Back-probe the control wire at the valve and command the valve on with the scan tool to verify the DME is pulling the circuit low
Check the control wire for a short to battery voltage with the key on and the DME disconnected, repairing the harness if voltage is present
Verify power and ground at the valve, then re-test the circuit after repair and clear the fault
Complete an evaporative system monitor drive cycle to confirm the repair and readiness for emissions testing

What a high purge signal really tells you

A high signal on the control circuit often means the valve coil is open, so the DME sees battery voltage on the command wire instead of the expected pull-down, which is why the valve itself is the most common fix.
Technicians sometimes replace the DME when the real fault is a chafed control wire shorting to voltage near the intake manifold, so always ohm and load-test the harness before condemning the module.
The purge valve can fail intermittently with heat, so a cold resistance check may pass while the fault only sets after the engine bay reaches operating temperature.
A stuck-open purge valve can cause a rough idle and fuel trim drift without setting P1440, so do not assume every purge fault is a high-signal circuit problem.
BMW evaporative monitors run under specific fuel level and temperature conditions, so the code may not reset immediately after repair until the correct drive cycle is completed.

Can I keep driving with P1440?

The car is safe to drive with P1440 because the purge valve defaulting closed only affects evaporative emissions and does not risk engine damage. Avoid topping off the fuel tank past the first click and get the circuit checked soon, especially if you smell fuel vapor or notice a rough idle after refueling.

Tools that help

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