P0443 fix: Purge Control Valve Circuit Malfunction

P0443 Evaporative Emission Control System Purge Control Valve Circuit Malfunction

The key to diagnosing a P0443 is in its definition: Evaporative Emission Control System Purge Control Valve Circuit Malfunction. That means the computer has detected a circuit issue. That can be caused by an open in the purge valve solenoid windings, a short to ground in the valve’s windings, a bad or corroded electrical connector to the valve, or a wiring harness issue. If you really want to do a P0443 fix once, don’t automatically assume it’s a bad purge valve. Do some diagnostic testing first.

The valve is a high failure rate item, but I’ve also seen wiring harness issues cause this code

In many cases, it’s a bad purge valve. However, I’ve seen

Purge valve

many instances where the problem is in the electrical connector or harness. In my experience, you should always check the condition of the electrical connector first before automatically replacing the purge valve.

I recommend checking for corrosion on the connector pins, bent pins, or signs of rodent damage on the insulation in the wiring harness.

If the connector and harness look good, you can use a multimeter to check for good power and ground by following the test procedure in the shop manual. If power and ground check out, then replacing the purge valve is the most common P0443 fix.

How the purge valve works

After you’ve filled with gas and started the engine, the ECM will start a purge cycle to clear the fuel vapors out of the charcoal canister and get it ready for the next fillup. The ECM opens the purge and vent valves. Engine vacuum sucks the fuel vapors from the canister, and the canister is purged by fresh air coming in through the vent valve. The ECM detects a rise in RPM from the additional fuel. However, once the canister is purged and fresh air is coming into the engine from the purge valve, it knows the canister is fully purged. It then closes the vent valve but leaves the purge valve open. That puts the entire fuel system under a vacuum. The ECM monitor the vacuum. If the vacuum drops, that’s the sign of a leak.

If you have P0443 Evaporative Emission Control System Purge Control Valve Circuit Malfunction, read this article for a full explanation of how the evaporative emissions system works.

To learn more about EVAP system, read this article

© 2012 Rick Muscoplat