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P0443: Evaporative Emission Control System Purge Control Valve Circuit Malfunction

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What is P0443?

P0443 is a diagnostic trouble code (DTC) defined as “Evaporative Emission Control System Purge Control Valve Circuit Malfunction.

It’s a generic engine code that is triggered when the Engine Control Module (ECM) or Powertrain Control Module (PCM) detects a malfunction with the purge control valve or its control circuit.

So what does that mean? 

Your vehicle’s Evaporative Emission System (EVAP) seals the fuel system of the vehicle to prevent fuel vapor from the fuel tank (gas tank) and fuel system from escaping into the atmosphere.

The fuel vapor is stored in the EVAP charcoal canister that has a purge valve controlled by a solenoid.

The purge valve solenoid is supplied with switched battery voltage.

The ECM controls the EVAP canister purge valve by operating the ground circuit and opening the purge valve at specific times. This allows the fuel vapor trapped in the charcoal canister to enter the intake manifold and subsequently be used in combustion.

The ECM monitors the functioning of the ground circuit as well: 

  • When the purge solenoid isn’t activated, the ECM sees a high voltage on the ground circuit. 
  • When the solenoid is activated, the ECM sees the ground voltage pulled low, close to zero. 

If the ECM doesn’t see the expected voltages or senses an open circuit, code P0443 is set, and the engine light is triggered.

Common symptoms

The exact symptoms associated with DTC P0443 can vary depending on the severity of the issue and the vehicle model. However, there are some common signs that indicate EVAP code P0443.

They are:

  • Check Engine Light turns on
  • Poor engine performance
  • Poor fuel economy
  • Excess pressure in the fuel tank

Can I still drive?

DTC P0443 is not an overly serious fault code. So you can drive your car with an active P0443 code.

However, it indicates a purge control valve circuit malfunction that may sometimes affect your car’s fuel economy and engine performance. So it’s best to contact a mechanic and get it fixed to avoid costly repairs in the future.

P0443 causes

Code P0443 can be caused by various factors concerning your car’s Evaporative Emission System (EVAP). Some of them may include:

  • Faulty or damaged purge solenoid
  • Faulty vent valve solenoid
  • Worn or damaged circuit connector
  • Damaged or corroded circuit wiring
  • The wiring harness chaffing or rubbing against another component, causing an open circuit or a short circuit
  • A bad driver circuit condition inside PCM (Powertrain Control Module) (very rare)

Note: Although the code indicates problems with the canister purge valve, a faulty purge control circuit can also trigger your car’s Check Engine Light.

Diagnosis

Here’s how a mechanic would go about diagnosing EVAP code P0443:

  1. Connect the engine to an OBD-II scanner and capture freeze frame data to identify similar trouble codes.
  2. Check the fuel tank pressure readings to identify a faulty fuel tank pressure sensor. If the fuel tank pressure sensor is faulty, the system will think there is no pressure or vacuum being made.
  3. Check all the accessible components and hoses in the Evaporative Emission System. Look for signs of wear and tear.
  4. Check the fuel cap (gas cap) and make sure it fits nicely to the gas tank filler neck.
  5. Look for a cracked or damaged fuel cap. If the gas cap is unable to hold pressure or vacuum, it will trigger the error code.
  6. Check the purge valve and the vent valve. Both should be able to hold a vacuum for a specified amount of time (at least 30 to 60 seconds). Perform a smoke leakage test on the fuel vapor system to try and locate the cause of the vapor leak within the vacuum line.
  7. If each of the components seems to be working properly, then the next test should be the ‘smoke test’ for the whole EVAP system. This test will search for any hidden leaks in the EVAP system.

What are the mistakes to avoid during P0443 diagnosis?

One of the most common mistakes when fixing any purge valve circuit issues is to preemptively change the wiring harness, vacuum line, ECM connector, purge valve connector, or any other circuit harness.

Ideally, you should wait to fully diagnose the root cause of your problem before making any repairs. For example, you could have a problem with the EVAP monitor or the purge valve vent, in which case changing the wiring harness would do no good.

Additionally, code P0443 can sometimes indicate deeper problems with the intake manifold or the Powertrain Control Module. In this case, it’s best to let a professional mechanic handle the diagnosis and repair.

Possible repairs for P0443 & Costs

Depending on the root cause of code P0443, a number of repairs can be implemented to clear the code. These include:

  • Testing and then replacing the purge control valve
  • Repairing the damaged wiring to the purge control valve
  • Repairing or replacing the purge vent valve
  • Engine Control Module (ECM) circuit replacement (very rare)

Repair Costs

You can expect to pay about $100-$150 for diagnosing code P0443 from a repair shop. From there, your mechanic will recommend the necessary repairs and charge you accordingly.

One of the main repairs for code P0443 is purge valve replacement. For that, you may have to pay about $80 to $200 in total. In this, labor costs amount to about $50 to $80, while parts can range from $30 to $120.

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