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Evaporative Emission System Purge Control Valve Circuit

Error Code P0443 is described as the Evaporative (EVAP) Emission System Purge Control Valve Circuit. This means one of the purge valve is malfunctioning or the purge valve circuit is short or open.


The ECM operates the ground circuit to control the valve, which opens the purge valve at specific time intervals, allowing gas to get into the engine. The ECM also monitors the ground circuit for faults. If the purge solenoid is not activated, the ECM should see high voltage on the ground. If it is activated, the ECM should show the ground voltage pulled to be low and close to zero.

In this error code, the EVAP system allows the fumes to enter the engine to be burned, rather than expelling to the atmosphere as emission. The purge valve solenoid is supplied from the switched battery voltage, which means there’s an improper flow of purge in the EVAP system. This can be caused by a defective purge valve or a shorted purge valve circuit.

Unburned drops of raw fuel are harmful for health and the environment as it can cause breathing problems and contributes to smog.

EVAP System Digram Drawing About the EVAP System

The job of the EVAP emission system is to capture and keep any raw fuel and fuel vapor from the fuel storage system, which includes the fuel tank, fuel neck cap and filler neck. These captured fuel vapors are sent back to the combustion process by the EVAP system, under precise operating conditions, which is dictated by the speed, load and temperature of the engine.

Common Symptoms

  • Check Engine light is on
  • Noticeable fuel odor caused by escaping water vapor
  • Rough running engine caused by stuck open purge valve (can be accompanied with different EVAP codes)
  • ”Whooshing” sound caused by excessive pressure in the gas tank when removing the cap, which indicates malfunctioning or stuck closed purge valve

Possible Causes

This error code refers to an issue with the purge control circuit, not automatically the valve. The problem is usually in the unit that houses the valve and solenoid (in the assembly), or could be a defect of a individual solenoid with purge valve or vacuum lines. This means the problem could be a result of any of the following:

  • Defective purge solenoid condition (open or internal short)
  • Worn out, broken or shorted connector caused by water intrusion
  • Chafing of wiring harness or grinding of another component, causing open or short control circuit
  • Bad driver circuit condition inside PCM (Powertrain Control Module)

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