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Error Code P0444 is defined as Evaporative Emission Control System Purge Control Valve Circuit Open. Meaning, there’s an excessive low voltage signal is sent to the PCM through the valve.
This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II, especially made since 1996 up to present. Specifications on the definition, troubleshooting and repairs of course, vary from one make and/or model to another.
For vehicles with EVAP (Evaporative Emission Control Systems), their engine draws in excessive fuel vapors through the gas tank that would otherwise be vented to the atmosphere.
The fuel vapor is routed through a vacuum line to the engine’s intake, while the purge valve or solenoid meters the anticipated level of fuel vapors. All of these are controlled by the PCM (powertrain control module, also known as ECM or engine control module in other makes). The PCM checks the voltage to the purge control valve, and if it unable to detect change with purge valve commanded on, it will trigger the Error Code P0444.
As with other error codes, this code activates the Check Engine light, which is also its most common and noticeable symptom. Other common symptoms include:
- Noticeable fuel odor caused by released fuel vapors
- Engine idles, stalls or hesitates
In most cases, the vehicle will not display noticeable conditions relating to the drivability of the vehicle. There may be a slight increase in fuel consumption, but it the error code will not affect the engine’s performance.
There are multiple of factors that causes this error code, some of the most common are:
- Disconnected or loose wiring harness
- Open circuit engine wiring harness
- Open circuit purge control solenoid
- Defective PCM (rare)
How to Check
As with most trouble codes, P0444 can be identified with the use of OBD-II code reader. Technicians start their diagnosis by checking all components and lines relating to the EVAP; they will look for signs of wear, damage and/or disconnection within the lines. If the vehicle is turned on, the technician may be able to pinpoint a potential leak in the vacuum by simply listening to the abnormal suction sound of the vacuum lines. Some technicians will also use a smoke machine to fill the EVAP system with smoke and find a leak through visual indication of escaping smoke.
How to Fix
Repairs for this error code are pretty simple and straightforward, but the success of the repair is highly dependent on the diagnosis. For one, the EVAP system must be checked thoroughly, before proceeding to any repair procedures. Some of the most common fixes are:
- Broken or faulty wirings must be repaired, if not replaced as needed
- Defective components in the EVAP system must be replaced upon diagnosis
- The system must be retested following each repair to limit unnecessary troubleshooting
- The vehicle must be taken to a test drive after repair to ensure the problem is resolved, and does not come back
This error code can be quite tricky to solve, as sometimes the issue is not in the EVAP itself, rather in the vacuum leak elsewhere. This is why it is important to diagnose thoroughly. Simple cases like an improperly tightened fuel cap may result into symptoms of this error code. Many people mistakenly replace some parts of the EVAP that are actually functioning properly. Thus, make sure you check the vacuum lines and fuel caps beforehand to rule out the possibility of the problem.