P0443 to P0445: EVAP purge valve control circuit

The purge valve is the one EVAP component that lives in the engine bay rather than under the car. That makes it accessible, testable and, when it fails, straightforward to replace.

Code	Meaning
P0443	Purge control valve circuit malfunction
P0444	Circuit open
P0445	Circuit shorted

Related: P0440 to P0446 EVAP purge and vent valve and P0441 incorrect purge flow.

Circuit codes are electrical

That is the key distinction. These are not flow codes and not leak codes.

• P0444 — open circuit. A broken wire, a disconnected connector, or an open solenoid winding.
• P0445 — short circuit. Usually a chafed wire touching ground or power, sometimes a shorted solenoid.
• P0443 — general circuit malfunction, which some manufacturers use for either.

The valve is normally switched on its ground side by the ECU, with battery voltage supplied through a fuse or relay.

The three-minute test

You need a multimeter and access to the valve. On most engines it is on or near the intake manifold with a vapour hose and an electrical connector.

1. Check resistance across the solenoid. Typical values sit in the 20–40 Ω range; check your specification.

Reading	Meaning
Within specification	Solenoid electrically healthy
Infinite / open	Winding failed — explains P0444
Near zero	Shorted winding — explains P0445

2. Check supply voltage at the connector with ignition on. No voltage means the fault is the fuse, relay or wiring, not the valve: fuses and relays basics for owners.

3. Apply battery voltage briefly to the solenoid off the vehicle. It should click audibly. A silent valve with correct resistance is mechanically seized.

Why it fails

Charcoal dust

The canister degrades over time and sheds fine carbon dust into the vapour line. That dust reaches the purge valve and jams it. This is the most common mechanical failure.

A valve that failed because of canister dust will do it again unless the canister is addressed.

Heat

The valve sits on a hot engine. Solenoid windings and plastic bodies both suffer.

Connector

Vibration and heat cycles. Check the latch and the pin tension before condemning the valve.

The ECU driver

Rare, but a shorted valve can take the output transistor with it. If a new valve sets P0445 immediately, that is the reason to consider.

The stuck-open symptom

Worth knowing because it produces a driveability complaint rather than a silent code.

A purge valve stuck open lets fuel vapour into the intake continuously, including at idle when the engine does not want it. Symptoms:

• Rough or unstable idle: fluctuating idle RPM causes.
• Rich running and negative fuel trim.
• Difficulty starting after refuelling, when the canister is fully loaded.

That last one is a strong clue. If the car is hard to start immediately after a fill and fine otherwise, look at the purge valve.

Watch fuel trim to confirm

The purge valve’s effect is visible in the data without any tools.

At a warm idle, watch short-term fuel trim. When the ECU commands purge, trim should move negative briefly as vapour arrives, then recover.

Behaviour	Meaning
Trim dips when purge commanded	Valve working
No change at all	Valve stuck closed or no flow
Trim permanently negative	Valve stuck open

Fuel trim STFT and LTFT explained.

After replacing it

1. Clear the code.
2. Check fuel trims settle near zero at idle.
3. Drive a full cycle to let the EVAP monitor run. It is fussy about conditions — roughly half a tank, a cold start, and a steady drive: how the EVAP monitor works.
4. Confirm readiness shows complete before an emissions test: OBD readiness monitors explained.

Step three catches people out. The monitor may take several days of normal driving to run, so a car that shows no code is not yet a car that has passed the test.

You can check this yourself. Pair an ELM327 adapter, open the free tier of the app and watch short-term fuel trim at a warm idle. A trim that never moves and a trim stuck negative point at opposite failures of the same valve.