Technical Description of OBD-II Trouble Code
Circuit for Controlling the Purge Valve of the Evaporative Emission Control System
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The Evaporative Emissions System (EVAP) allows fumes from the gas tank to enter the engine for combustion instead of being released into the atmosphere as emissions. The purge valve solenoid is supplied with switched battery voltage.
The ECM controls the valve by operating the ground circuit, opening the purge valve at specific times to allow these gases to enter the engine. The ECM also monitors the ground circuit for faults. When the purge solenoid is not activated, the ECM should detect a high voltage on the ground circuit. When the solenoid is activated, the ECM should detect the ground voltage being pulled low, close to zero. If the ECM does not detect these expected voltages or senses an open circuit, this code is set.
Note: This DTC is similar to P0444 and P0445.
Potential Symptoms
The symptoms of trouble code P0443 could be limited to the illumination of the malfunction indicator lamp (MIL). There may be no drivability issues at all. However, it is also possible to experience a lean condition or a rough running engine if the purge valve is stuck open. Usually, these symptoms are accompanied by other EVAP codes. Another symptom may be excessive pressure in the gas tank, indicated by a “whooshing” sound when the cap is removed, which suggests a purge valve that is not functioning or stuck closed.
Causes
To trigger a P0443 code, there must be a problem with the purge control circuit, not necessarily the valve itself. Usually, the valve and solenoid are housed together as an assembly. Alternatively, it could consist of a separate solenoid with vacuum lines leading to a purge valve. That being said, the following could be the cause:
Possible Solutions
1. Using a scan tool, command the purge solenoid to activate. Listen or feel for a clicking sound coming from the purge solenoid. It should click once, or on some models, it may click repeatedly.
2. If the solenoid does not click when activated with the scan tool, unplug the connector and inspect the solenoid and connector for damage or water intrusion. Then, with the key on, check for battery voltage on the feed wire. If there is battery voltage, manually ground the control side using a jumper wire and see if the valve clicks. If it does, it indicates that the solenoid is functioning properly but there is an issue with the control circuit. If the valve does not click when manually grounded, replace the purge solenoid.
3. To check for a problem in the control circuit (if the solenoid tests okay and there is voltage to the solenoid), plug the solenoid back in and remove the control circuit (ground) wire from the ECM connector (If you’re unsure how to do this, do not attempt). With the ground wire disconnected from the ECM, turn the key on and manually ground the Purge valve control wire. The solenoid should click. If it does, it indicates that there is no problem with the control wire to the solenoid and there is an issue with the ECM purge solenoid driver circuit. A new ECM will be required. However, if the solenoid does not click, there must be an open in the wiring between the ECM and the solenoid. It is necessary to locate and repair the open circuit.
Other EVAP DTCs: P0440 – P0441 – P0442 – P0444 – P0445 – P0446 – P0447 – P0448 – P0449 – P0452 – P0453 – P0455 – P0456
