Safe to drive. Repair before the next emissions test. P0443 means the ECM has detected that the EVAP purge control valve circuit is not responding to its commanded drive signals -- indicating a failed purge valve solenoid, open or shorted wiring, or a blown fuse on the valve supply circuit.
What P0443 means
The evaporative emission (EVAP) system stores fuel vapour from the fuel tank in a charcoal canister, then purges that stored vapour into the intake manifold for combustion once the engine is warm. The ECM controls a purge VSV (vacuum switching valve) or purge solenoid by sending a timed duty-cycle signal and simultaneously monitoring the circuit's electrical response. When the measured terminal voltage at the ECM's output pin does not correspond with its commanded on/off state -- for example the ECM commands the valve open but detects an open circuit, or commands it closed but sees a short to ground -- P0443 is set as a 1-trip code. This is a circuit integrity fault, not a vapour-flow or leak fault; it confirms the valve or its wiring is not responding electrically to ECM commands.
Symptoms
- Check engine light (MIL) illuminated -- typically the only symptom in most driving conditions
- Fuel odour, especially after refuelling, if the canister cannot purge accumulated vapour
- Slightly elevated fuel vapour emissions flagged in emissions testing
- Failed OBD-II EVAP system monitor readiness (monitor stays INCOMPLETE during drive cycle)
- Rough or slightly lean idle in some cases if the purge valve sticks open, drawing unmetered air into the intake
Common causes
- Failed purge VSV solenoid -- internal open or short in the coil (resistance spec is 23-26 ohms at 20 C on Toyota systems)
- Open circuit in the purge valve wiring between the ECM output pin and the valve's ground terminal
- Short to ground on the ECM control wire, keeping the valve energised continuously
- Blown fuse on the purge valve power supply circuit (EFI relay or dedicated EVAP fuse)
- Corroded or loose connector at the purge VSV causing intermittent signal inconsistency
- Failed ECM driver transistor for the purge control output (rare)
Severity & driving advice
Severity: Low — No drivability impact in most conditions. A stuck-open valve can cause lean idle. Emissions-test failure is likely. Repair within 1-2 months.
Can I drive? Safe to drive. Repair before the next emissions test.
Diagnostic approach
- Check purge valve function with a scan tool active test — Connect a scan tool and navigate to the EVAP or purge valve active test. Command the purge VSV on and off while holding a finger over the canister-side vacuum hose port on the valve. When commanded ON the valve should apply suction (vacuum passes through). When commanded OFF no suction should be felt. If the valve does not respond mechanically to the command, proceed to the resistance check.
- Measure purge VSV solenoid resistance — Disconnect the purge VSV connector and measure resistance between the two solenoid terminals. On Toyota systems the specification is 23-26 ohms at 20 C (68 F). Values significantly below this indicate a shorted coil; infinite resistance (OL) indicates an open coil. Either reading confirms the valve has failed and should be replaced.
- Verify power supply voltage to the purge valve — With the purge VSV connector disconnected and the ignition on, measure voltage from the power-supply pin in the harness connector to body ground. It should read 11-14 V (battery voltage via the EFI relay). Zero volts indicates a blown fuse, failed relay, or open supply wire. Inspect the EFI main fuse and EFI relay in the engine room fuse block.
- Inspect the control wire from ECM to purge valve for open or short — With the purge VSV connector and the ECM connector both unplugged, measure resistance from the ECM control pin (labelled PRG on Toyota) to the purge valve harness control pin -- should be below 1 ohm. Measure the control pin to body ground -- should be above 10 kohm. If below 1 kohm to ground, the control wire is shorted. Trace the harness along the firewall and under the intake manifold for damage.
- Replace the purge VSV and retest — If solenoid resistance is out of specification and wiring checks are normal, replace the purge VSV. After replacement, clear the code and run an EVAP monitor drive cycle (cold start, drive at varying speeds with several deceleration events) to confirm the monitor completes and passes.
Make & model notes
Toyota: Toyota uses a purge VSV (vacuum switching valve) on many engine families including the 4.0L 1GR-FE in FJ Cruiser, 4Runner, and Tacoma. The solenoid coil resistance spec is 23-26 ohms at 20 C. Note that on Mexican-market FJ Cruiser models the P0443 data is specifically tagged as applicable to Mexico models only -- North American models with the closed EVAP system may use different purge control logic. Verify your emission system type before diagnosis.
Ford: Ford F-150 and Explorer with 5.0L and 3.5L EcoBoost engines use a canister purge solenoid near the charcoal canister. A corroded 2-pin connector is a common cause of P0443 on these models. Inspect the connector body for green corrosion before replacing the solenoid itself -- connector replacement often cures the fault.
FAQ
Can a P0443 cause my car to fail an emissions test?
Yes, in two ways. First, the code itself causes a test failure in states with OBD-II plug-in testing. Second, if the purge valve is not functioning, the EVAP system readiness monitor may remain incomplete, which also causes failure in most states. Fix the fault and run a complete drive cycle before retesting.
Is P0443 the same as an EVAP leak code?
No. P0443 is an electrical circuit code -- the purge valve's wiring or solenoid has an electrical problem. EVAP leak codes like P0442, P0455, or P0457 indicate that vapour is escaping from the fuel system through a physical hole or an unsealed fuel cap. The two can occur together but are independent faults with different diagnoses.
What happens if the purge valve is stuck open?
A stuck-open purge valve draws unmetered fuel vapour directly into the intake manifold at all times, including at idle. This causes a lean-biased or erratic idle because the ECM's fuel trim is not calibrated for the continuous vapour flow. The lean condition can also set separate fuel trim codes like P0171 on Bank 1.
How long does it take to run the EVAP monitor after fixing P0443?
The EVAP monitor typically requires a cold start (coolant temperature below 35 C) followed by a warm-up and highway drive cycle, then a deceleration. On most vehicles this takes one to two complete drive cycles after the repair. Clearing the code resets all readiness monitors; avoid emissions testing until you have confirmed all monitors show READY.