P0443 Code: Evaporative Emission System Purge Control Valve “A” Circuit

The evaporative control (EVAP) system helps prevent fuel vapors from being released into the atmosphere. Depending on the issue experienced by the EVAP system, your car’s primary computer, which is often referred to as the powertrain control module (PCM), can log different diagnostic trouble codes—one such code is a P0443.

What Does the P0443 Code Mean?

Diagnostic trouble code (DTC) P0443 stands for Evaporative Emission System Purge Control Valve “A” Circuit. The code indicates that the PCM perceives a problem with the EVAP system purge valve or its control circuit.

Like the P0443 code, the P0444 code (EVAP Purge Control Valve Circuit Open) and P0445 code (EVAP Purge Control Valve Circuit Shorted) also relate to the purge control valve.

Examples of other diagnostic trouble codes pertaining to the EVAP system include P0440-P0449, P0452-P0453, and P0455-P0456.

P0443 on Some Ford Vehicles

Code P0443 may appear on some Ford vehicles. On a 2011 Ford F-150 XL 3.7L V6, for example, this DTC is described as, “The powertrain control module (PCM) monitors the state of the EVAPCP circuit output driver. The test fails when the signal moves outside the minimum or maximum limit for the commanded state.”

The code appears in a 2011 Ford F-150 XL 3.7L V6 because of the following conditions:

• VPWR circuit open
• EVAPCP circuit short to ground
• EVAPCP circuit open
• EVAPCP circuit short to voltage
• Damaged EVAP purge valve
• Damaged PCM

For this specific vehicle, Ford also notes that to verify normal function, monitor the EVAP purge valve signal PID EVMV or EVAPCP and the signal voltage (PCM control side). With the valve closed, the EVMV indicates 0 mA (0% duty cycle for EVAPCP) and voltage approximately equal to battery voltage. When the valve is commanded fully open, EVMV indicates 1,000 mA (100% duty cycle for EVAPCP) and a voltage drop of 3 volts minimum is normal.

Note: Although code P0443 is a generic code specified by the Society of Automotive Engineers (SAE), the code’s definition may be different depending on the vehicle manufacturer.

What are the Symptoms of the P0443 Code?

In many cases, the only symptom that would accompany the trouble code P0443 is an illuminated check engine light. However, you may observe other telltale signs, particularly if there are other codes stored in addition to P0443.

If that is the case with your vehicle, the causes and symptoms may differ from those listed here.

Here are the two most common symptoms:

• An illuminated check engine light
• Engine performance problems, such as rough running and hesitation (if the purge valve is stuck open)

What are the Causes of the P0443 Code?

The following problems can prompt the PCM to log a P0443 code:

• A bad purge valve
• Problems with the purge valve circuit, such as loose connections and damaged wires
• A problem with the PCM (rare)

How to Diagnose the P0443 Code

Typically, either a circuit fault or problem with the purge valve will trigger code P0443. Because diagnosis can be tricky, if you’re uncertain of your automotive aptitude, you may want to leave the task to a professional.

However, if you’d like to perform the diagnosis yourself, check out the videos below to get an idea of what the troubleshooting process involves:

How to Fix the P0443 Code

By now, you probably get the idea: There is no “magic bullet” fix for code P0443. What complicates things further is the fact the diagnosis and repair of the problem can vary by vehicle.

That’s why only vehicle owners with sufficient technical knowledge should attempt DIY fixes on a vehicle with a P0443 code. Otherwise, bring the vehicle to the nearest auto repair shop and get a trained professional to repair the problem.

If you do decide to tackle fixing the code yourself, keep in mind that different types of vehicles may require their own distinct solutions. For that reason, you should always consult the appropriate repair information for your application.

Repair manuals, such as those from Chilton, are useful, but an ALLDATA subscription is even better. ALLDATA has single-vehicle subscriptions for DIYers that provide detailed factory repair information.

The EVAP System and Purge Valve

As mentioned, the EVAP emissions system prevents fuel vapors from being released into the atmosphere. The heart of the system is the charcoal canister—a device that traps the fuel vapors when the engine is off.

The canister purge valve is typically a valve opened by a solenoid that is duty cycled by the ECM/PCM to allow fuel vapor stored in the canister to enter the intake manifold. The ECM/PCM knows when it is purging and there are “cells” in the algorithm map that factor in canister purging for air fuel mixture control purposes, because adding fuel vapor to the intake has an impact on fuel trim strategy. Cells where no purging is supposed to take place are flagged by the algorithm as “purge free” cells.

The B+ side of the purge solenoid will typically be fed by a relay, and the ground side of the solenoid will be duty-cycled by the ECM/PCM as the algorithm dictates. (For a technical understanding of EVAP systems, you can read our discussion here.)

Once the engine is running and conditions are correct, the PCM commands the purge valve open to allow the vapors to enter the engine. The vapors are then burned during the normal combustion process.

The PCM monitors the integrity of the purge valve and the valve’s control circuit. When the module detects an electrical fault with either the valve or the circuit, it will set code P0443.

Where to Get a New Purge Valve for Your Vehicle

Your daily driving duties will continue to be a hassle if you don’t replace your defective purge valve. A rough-running engine and hesitation are only the beginning of your troubles, and soon after you’ll be left with an expensive repair bill.

Don’t let your vehicle hang out in the garage for days because of a damaged purge control valve. Order a top-notch replacement right here at CarParts.com. All our products passed the highest quality control standards from industry professionals, so you’re sure to get a purge valve that’s built to last.

With only a few clicks, you can find the right part for your ride on our website. Use our vehicle selector to start shopping, and funnel the catalog results according to your preferences using the search filters.

Here at CarParts.com, you’ll never go over budget while shopping for your automotive needs. All our products come with a low-price guarantee to help you get the best value for your money. Order now, and we’ll deliver your new purge valve straight to your doorstep in as fast as two business days.

Get your daily driving running like it’s as good as new, and shop for an OE-grade purge valve today!

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