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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. If the ECM can’t see the expected voltages, or detected open circuit, it will trigger the error code.
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.
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.
- 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
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)
How to Diagnose
Step 1 – Get the code and jot down the freeze frame info for a baseline test and to verify your repair.
Step 2 – Check all accessible components and hoses in the EVAP system. Look for any signs of wear and tear.
Step 3 – Use a scan tool and check the Fuel Tank Pressure readings. If the Fuel Tank Pressure sensor is not working properly, the system will think there is no pressure or vacuum being made when EVAP monitor is done, even if there is actually pressure/vacuum being made. The PCM depends on the Fuel Tank Pressure Sensor’s leak test data when the EVAP monitor runs.
Step 4 – Check the fuel cap and make sure it fits nicely to the fuel tank filler neck. Also, make sure the cap seal is NOT cracked or dry. If the cap is unable to hold pressure/vacuum, then it will trigger the error code.
Step 5 – Check the Purge Valve, as well as the Vent Valve. Both should be able to hold vacuum for a specified amount of time (at least 30 to 60 seconds). If one of the valves is malfunctioning, the system will not respond and/or hold the right amount of vacuum.
Step 6 – If each of the components you check seems to be working properly, then your next test should be the ‘smoke test’ for the whole EVAP system. This test will search for any hidden leaks all throughout the under components of your vehicle.
How to fix
- Using the error code scanning tool, activate the purge solenoid. Pay attention for clicking sounds coming from purge solenoid. The purge solenoid should click once (or repeatedly for other models).
- If there is no clicking sound upon using the scanning tool, then you have to disconnect the connector and check both the connector and the solenoid for signs of water, damage, etc. Then, inspect voltage of the battery through the feed wire, with the key on. If there’s voltage in the batter, then use a jumper wire to manually ground the control side to see if the valve clicks again. If it clicks, then that means your solenoid is in good condition, and the problem is in the control circuit. If it still doesn’t click after manual grounding, then you need to replace your solenoid.
- To diagnose your control circuit (if the result of the solenoid test is good, and you have solenoid voltage), connect the solenoid back and disconnect the control circuit (ground) wire from the ECM connector. (If you are NOT sure how to do this, then DO NOT attempt, and leave it to a professional technician).
With your ground wire removed from the ECM, turn on the key and then ground the Purge valve control unit manually. There should be a ‘click’ sound from the solenoid. If there’s none, then there might be an opening in the wiring between the solenoid and the ECM. You need to find this opening and fix it
If there is a ‘click’ sound from the solenoid however, this means the control wire connected to the solenoid is in good shape, and the problem is in the ECM purge solenoid driver circuit of the ECM.
For more about EVAP error codes, or for more comprehensive and thorough professional help, Contact Us.