Emissions and evaporative
P0443EVAP purge control valve circuit
EVAP System Purge Control Valve A Circuit
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Generic OBD-II code
Evaporative Emission (EVAP) System Component
What this part does
Captures and purges fuel vapor from the fuel tank/charcoal canister into the engine rather than releasing it to the atmosphere; includes the purge and vent solenoids and related sensors.
What the computer is measuring
Petrol evaporates in the tank, and letting that vapour into the atmosphere is not permitted. The evaporative emissions system captures it in a charcoal canister instead, holds it there, and then feeds it into the engine to be burnt at moments when doing so will not upset the fuelling. The part that lets it in is the purge valve.
The purge valve is an electrically operated solenoid. The computer commands it open by a percentage, pulsing it so that a controlled amount of vapour is drawn in by manifold vacuum. Like most solenoid outputs, the computer monitors the circuit rather than trusting it, watching the current flowing when it energises the coil.
P0443 is the result of that monitoring failing. The circuit did not behave the way an intact solenoid on intact wiring behaves. It is a circuit code, and that is what separates it from the rest of the evaporative family.
How this differs from the leak codes
Most evaporative codes people meet are leak codes. The computer seals the system, applies vacuum or pressure, watches how it holds, and reports a small or a large leak. Those codes send you looking for a loose fuel cap, a perished hose or a cracked canister.
P0443 is not one of those. It never got as far as testing for a leak. It is reporting an electrical problem with the valve circuit itself, which means the fuel cap is not the answer here and neither is a smoke test. Start at the connector, the coil and the wiring.
The reverse is also worth knowing. A purge valve stuck mechanically open, drawing vapour in continuously, upsets idle and can push the mixture rich, and that may show up as a rich or an idle code rather than as this one. If the car idles badly and has been hard to start just after a fill up, check what the valve is doing mechanically as well as electrically while it is off the car.
What you will notice
- Check engine light on with nothing else wrong, which is the usual case.
- A rough idle or a stall shortly after refuelling if the valve is stuck open.
- Difficulty starting immediately after filling up, then normal running once it clears.
- An emissions test failure, because the evaporative monitor cannot complete.
Likely causes, most common first
Ordered by how often each one actually turns out to be the problem, not alphabetically and not by part price.
A failed purge solenoid
The most common cause. The coil goes open circuit or shorts, and the computer sees the current it expects on that circuit disappear or spike.
A damaged connector or chafed wiring at the valve
The valve is usually mounted on or near the intake manifold, where heat cycling hardens the connector and cracks the insulation.
A blown fuse or an open supply circuit
Cheap to check and often shared with other components, so look for other codes that would point at the same fuse.
A corroded or loose ground
A ground that has degraded raises circuit resistance until the current no longer looks right to the module.
A failed driver inside the engine control module
Rare, and only a reasonable conclusion once the solenoid, the wiring and the supply have all been proven good.
What to check, in order
Command the purge valve on and off with a scan tool while listening or holding a hand on it.
A clean click each time means the valve and its circuit are working, so the fault is intermittent and needs catching while present. No click sends you to the coil and the wiring.
Measure the resistance across the solenoid coil.
An open circuit or a very low reading confirms a failed solenoid. A sensible reading in the tens of ohms clears the valve itself and moves the fault into the harness.
Check for supply voltage at the valve connector with the ignition on.
No supply moves the fault back to the fuse and the supply wiring. Supply present with a good coil leaves the control wire and the module driver.
Check the control wire back to the module for an open circuit or a short.
A fault found in the wiring is the answer. A sound control wire with a good coil and a good supply is the only situation where the module driver becomes a fair conclusion.
While the valve is out, check whether it holds vacuum when closed.
A valve that leaks when commanded closed explains the rough idle and the hard starting after refuelling, and is worth knowing even though this code is about the circuit.
Where this one turns up most
- Vehicles where the purge valve is bolted directly to the intake manifold and takes engine heat continuously.
- Higher mileage cars where the valve has never been replaced and the connector has gone brittle.
Codes that often show up alongside it
What a DriveDecode adapter can read
A DriveDecode adapter reads engine and emissions systems: the powertrain and emissions codes the OBD-II standard requires on every US vehicle it covers. It does not read ABS, airbag (SRS), TPMS or transmission-specific manufacturer codes. Those need make-specific decoding that generic OBD-II hardware cannot do.
Reading P0443 on your own car
DriveDecode pulls P0443 straight off the vehicle along with the freeze frame the computer stored when it set: the coolant temperature, engine load and speed at that exact moment. That context is what separates a fault that happens on a cold start from one that happens under load, and it is the first thing the list above asks you to narrow down.
Last reviewed 2026-09-08. Definition sourced from the published standard.