What does error code P0443 mean?
The diagnostic code P0443 is a generic powertrain code, meaning it applies to all vehicles equipped with an OBD-II system. It indicates a problem in the control circuit of the Evaporative Emission (EVAP) system purge valve.
Operation of the EVAP System and the Purge Valve
The EVAP system is designed to prevent gasoline vapors from the fuel tank from escaping into the atmosphere. Instead, these vapors are directed to the engine to be burned. The purge valve is a key component of this system. It is powered by a switched battery voltage (present when the ignition is on).
The Engine Control Module (ECM) controls the opening and closing of this valve by actuating the ground circuit. At specific times, the ECM grounds the circuit, which allows the valve to open and fuel vapors to be drawn into the engine.
The ECM also monitors the integrity of this ground circuit to detect potential faults. When the purge valve is not activated (at rest), the ECM expects to see a high voltage on the ground circuit. When the valve is activated (grounded by the ECM), the voltage on the ground circuit should drop to a value close to zero. If the ECM does not detect these expected voltages or if it identifies an open circuit (interruption), the code P0443 is stored.
Important Note: This error code is similar to codes P0444 (EVAP purge valve control circuit open) and P0445 (EVAP purge valve control circuit shorted).
Potential Symptoms of Code P0443
The symptoms associated with fault code P0443 can vary:
- The most common symptom is the illumination of the Malfunction Indicator Lamp (MIL or Check Engine Light).
- There may be no noticeable driving issues.
- However, in some cases (if the purge valve is stuck open), you might observe a lean air-fuel mixture or engine misfire. These symptoms are usually accompanied by other EVAP system-related error codes.
- Another possible symptom is excessive pressure in the fuel tank, manifesting as an audible “hiss” or “squeal” when removing the fuel cap. This can indicate a purge valve that is not functioning at all or is stuck in the closed position.
Possible Causes of Code P0443
For a P0443 code to be stored, there must be a problem with the purge CONTROL CIRCUIT, not necessarily with the valve itself. Often, the valve and the control solenoid are integrated into a single unit. In other configurations, it may be a separate solenoid controlling the vacuum routed to a purge valve. That said, possible causes include:
- Faulty purge solenoid (with an internal short circuit or open circuit).
- Damaged wiring harness (rubbing against another component, causing a short or open in the control circuit).
- Worn, broken, or shorted electrical connector (often due to water intrusion or corrosion).
- Failure of the driver circuit inside the Powertrain Control Module (PCM).
Possible Solutions and Diagnostic Steps
Here are possible diagnostic steps to identify and resolve the problem related to code P0443:
- Activation Test via Scan Tool: Use an OBD-II scan tool to command the activation of the purge solenoid. Listen carefully or try to feel a “click” from the solenoid. It should click once per command, or on some models, it may click repeatedly.
- Diagnosis if the solenoid does not activate:
- If no click is heard during activation via the scan tool, unplug the solenoid connector.
- Visually inspect the solenoid and connector for physical damage, signs of water, or corrosion.
- Check for battery voltage on the solenoid’s power wire with the ignition on (key in ON position). If voltage is present, proceed to the next step.
- Manually ground the control side (usually the ground wire) of the solenoid using a test wire (jumper) and see if the valve clicks.
- If it clicks: This indicates that the solenoid is functioning correctly, but there is a problem in the control circuit (between the ECM and the solenoid).
- If it does not click: The purge solenoid is likely faulty and needs to be replaced.
- Checking the Control Circuit (if the solenoid works and power is good):
- Reconnect the solenoid.
- Locate and remove the control circuit wire (ground) from the ECM connector. (Caution: If you are unsure of the procedure, do not attempt this step to avoid damaging the ECM).
- With the solenoid’s ground wire disconnected from the ECM, turn the ignition on (key in ON position).
- Manually ground the purge valve control wire.
- If the solenoid clicks: This means there is no problem with the control wire between the ECM and the solenoid. The issue is likely with the purge solenoid control circuit inside the ECM, which will require replacing the ECM.
- If the solenoid does not click: There is likely an open circuit (break) in the wiring between the ECM and the solenoid. You will need to locate this break and repair it.
Other mentioned EVAP error codes: P0440, P0441, P0442, P0444, P0445, P0446, P0447, P0448, P0449, P0452, P0453, P0455, P0456. These codes indicate other types of problems within the evaporative emission system.