P0444
Evaporative Emission Control System Purge Control Valve Circuit OpenP0444 is a generic OBD-II powertrain diagnostic trouble code: Evaporative Emission Control System Purge Control Valve Circuit Open. It is logged by the engine control unit when the powertrain monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.
What P0444 means
P0444 is stored when the PCM detects an open circuit in the EVAP canister purge control valve circuit. The purge valve is a normally-closed solenoid that the PCM pulses open during warm cruise conditions to draw stored fuel vapours from the charcoal canister into the intake manifold for combustion. An open circuit means the PCM is commanding the valve but the expected current draw is absent — typically because of a broken wire, a disconnected connector, or a failed solenoid coil with very high resistance.
This code is an electrical circuit fault, not an EVAP leak. The distinction matters during diagnosis: P0444 (open) means the control signal cannot reach the valve, whereas P0440/P0442/P0455 address vapour leaks from the system plumbing. The purge valve is usually found on the intake manifold or near the charcoal canister, connected by a short wiring harness. Connector corrosion and harness damage near heat sources are the most common root causes.
Driveability impact is usually minimal — the engine continues to run normally on fresh fuel — but fuel vapour cannot be purged from the canister, so it may eventually saturate and allow raw vapour to escape to atmosphere. The MIL will illuminate and the EVAP monitor will report incomplete, causing an emissions test failure.
Common causes
Most-frequently reported root causes when P0444 is logged.
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1
Broken or open wire in the harness between the PCM and the purge valve connector.
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2
Disconnected or backed-out terminal in the purge valve electrical connector.
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3
Corroded connector pins causing high resistance or complete loss of continuity.
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4
Failed purge valve solenoid coil with an open internal winding.
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5
Blown fuse supplying the purge valve control circuit.
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6
PCM output driver fault that cannot sink current through the valve circuit (rare).
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7
Wiring damaged by heat from nearby exhaust components.
Symptoms drivers notice
How to diagnose P0444
A typical diagnostic flow when this code is present.
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1
Retrieve and record the code; check for companion EVAP leak codes (P0440, P0442, P0455) which would point to separate plumbing faults.
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2
Visually inspect the purge valve connector and harness for obvious damage, corrosion, or disconnection.
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3
With the connector plugged in, back-probe the control wire and measure voltage while the PCM commands the valve open (scan tool active test); no voltage change confirms an open in the supply or signal circuit.
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4
Unplug the purge valve and measure solenoid coil resistance between the two terminals; typical spec is 14–30 ohms — OL (open) confirms a failed valve coil.
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5
Check harness continuity from the purge valve connector pin back to the PCM pin; any break or high resistance confirms a wiring fault.
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6
Inspect and test the fuse for the purge valve circuit; replace if blown and investigate for an underlying short.
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7
If all wiring and the valve test good, test the PCM driver output with a lab scope before condemning the PCM.
Related powertrain codes
- P0400 — Exhaust Gas Recirculation Flow Malfunction
- P0401 — Exhaust Gas Recirculation Flow Insufficient Detected
- P0402 — Exhaust Gas Recirculation Flow Excessive Detected
- P0403 — Exhaust Gas Recirculation Circuit Malfunction
- P0404 — Exhaust Gas Recirculation Circuit Range/Performance
- P0405 — Exhaust Gas Recirculation Sensor A Circuit Low
Frequently asked questions
What is the difference between P0444 and P0445?
P0444 is an open circuit (too much resistance — broken wire, disconnected plug, or open coil), while P0445 is a short circuit (too little resistance — wiring shorted to ground or a coil that has failed shorted). The diagnostic approach is opposite: P0444 requires finding a break in the circuit, P0445 requires finding an unintended low-resistance path.
Can a bad purge valve cause a rich condition or rough idle?
A stuck-open purge valve can cause a rough idle or rich mixture, but P0444 means the valve circuit is open, so the valve cannot receive the command to open. An open-circuit purge valve will default to closed (no purge), so rich-running symptoms are unlikely with this specific code.
Is it safe to drive with P0444?
Yes, the vehicle is safe to drive. The purge valve being inoperative does not affect combustion directly. However, the canister will not be purged of stored vapours, eventually leading to saturation and a possible fuel smell. Prompt repair is recommended to restore emissions compliance.
How do I test the purge valve itself?
Unplug the purge valve connector and measure resistance across the two solenoid terminals with a multimeter. A typical healthy valve reads 14–30 ohms. An OL (open) reading means the internal coil is broken and the valve must be replaced. You can also apply 12 V and a ground directly to the terminals and listen for an audible click, confirming the valve mechanically operates.
Disabling P0444 in software
RaceTune can permanently disable P0444 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.
Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.
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