The engine computer opens the EVAP purge valve electrically so the engine can burn stored fuel vapor. A P0443 code means the computer found a problem in the purge valve control circuit.
This guide explains how the purge valve is controlled, what breaks its circuit and how to test it.
P0443 Code Breakdown
Every OBD-II code follows the same five-character pattern set by the SAE J2012 standard. Each character narrows down which system has the fault. This table shows what each part of the code tells you.
| Character | Meaning | What It Tells You |
|---|---|---|
| P | Powertrain | The fault is in the engine or transmission systems. |
| 0 | Generic (SAE) code | The definition is the same on every OBD-II vehicle. |
| 4 | Auxiliary emission controls | The fault involves emission control systems such as EGR, secondary air, EVAP or the catalytic converter. |
| 43 | Specific fault | Evaporative Emission Control System Purge Control Valve Circuit Malfunction |
What the P0443 Code Means
The SAE J2012 standard defines the P0443 code as Evaporative Emission Control System Purge Control Valve Circuit Malfunction. The evaporative emission control (EVAP) system traps gasoline vapor from the fuel tank so it does not escape into the air. The vapor is stored in a charcoal canister, then drawn into the engine and burned when the engine is warm and running.
Two valves control the system. The purge valve, sometimes called the purge solenoid, opens to let engine vacuum pull vapor from the canister into the intake. The vent valve opens the canister to fresh air, and closes so the system can be sealed for a leak test.
To test for leaks, the powertrain control module (PCM) seals the system and watches the fuel tank pressure sensor for a change. Some vehicles, including many Toyota, Volkswagen and Chrysler models, use a separate leak detection pump or module instead.
The purge valve is a solenoid. On most vehicles, it gets battery voltage from a fuse whenever the engine runs, and the PCM pulses its ground to open it. This general code covers any circuit fault the PCM sees.
Symptoms of a Purge Valve Circuit Fault
Most EVAP faults are hard to notice. Common signs of a P0443 code include:
- Check engine light on
- Other EVAP codes set at the same time
- Fuel smell
- Hard starting after refueling if the valve sticks open
- Failed emissions test
Many vehicles run normally with this code, since the purge valve only affects how stored vapor is handled.
Common Causes of the P0443 Code
These are the usual causes:
- Damaged wiring or connector. Heat and engine movement crack them.
- Failed purge valve coil. The coil opens or shorts.
- Blown fuse. Removes power from the valve.
- Corroded connector. Water gets in through a worn seal.
- PCM driver fault. Rare.
Tools You Will Need
You can do most of this testing at home with basic tools:
- OBD-II scan tool that can command the purge and vent valves
- EVAP smoke machine
- Digital multimeter
- Hand vacuum pump
- Replacement gas cap that meets the original spec
How to Track Down the P0443 Code
Start with the simplest checks. Many EVAP codes come from the gas cap or a cracked hose.
Find the Purge Valve
On most vehicles, the purge valve sits in the engine bay near the intake manifold, with one hose to the intake and one to the canister. Some vehicles mount it near the canister. Check the connector and wiring for damage.
Check Power and Ground
Unplug the valve and turn the key on or start the engine. Check for battery voltage on the feed wire with a test light. Then command the valve on with a scan tool and check that the PCM pulses the control wire.
Measure Coil Resistance
Measure across the valve terminals. Many purge valves read about 20 to 30 ohms, but check the specification for your part. An open or very low reading confirms a bad valve.
Check the Wiring
With the battery disconnected and the PCM unplugged, check the control wire for continuity end to end and for shorts to ground and power.
If the valve tests good and the wiring is fine, command it with a scan tool and listen for a click. A valve that clicks but leaks may also need replacing.
Repairs That Fix the P0443 Code
Match the repair to what your tests found. Then clear the code and drive under the same conditions that set it.
- Repair the connector or wiring.
- Replace the purge valve if its resistance is out of range or it sticks.
- Replace a blown fuse after finding the cause.
- Seal the connector to keep water out.
After the repair, clear the codes and drive normally. The PCM rechecks the purge circuit quickly, but the full EVAP monitor may take several days to complete.
Common Mistakes to Avoid
These mistakes waste money or leave the real fault in place:
- Replacing the canister when the code points to the purge valve circuit
- Ignoring a shorted coil that may have damaged the PCM driver
- Forgetting to check the fuse
Repair Cost Breakdown
The cost to fix a P0443 code depends on the cause. This table shows typical ranges for parts and labor.
| Repair | DIY Cost | Typical Shop Cost |
|---|---|---|
| Gas cap | $15 to $40 | $30 to $80 |
| Purge valve | $20 to $100 | $100 to $300 |
| Vent valve | $30 to $120 | $150 to $350 |
| EVAP hose or line | $10 to $60 | $100 to $300 |
| Charcoal canister | $100 to $400 | $300 to $800 |
The purge valve is an inexpensive part and is usually easy to reach. Wiring repairs are also low cost unless the damage is hard to get to.
Is It Safe to Drive with a P0443 Code?
Yes. EVAP codes do not affect how the engine runs in most cases, and they are not a safety risk on their own.
The vehicle will fail an emissions test, and a strong fuel smell can mean a larger leak or a fuel line problem, which should be checked right away. A purge valve stuck open can also cause hard starting after refueling.
Related Codes
These codes often show up with this one or point to the same system:
| Code | Meaning |
|---|---|
| P0440 | Evaporative Emission Control System Malfunction |
| P0441 | Evaporative Emission Control System Incorrect Purge Flow |
| P0442 | Evaporative Emission Control System Leak Detected (Small Leak) |
| P0455 | Evaporative Emission Control System Leak Detected (Gross Leak) |
| P0456 | Evaporative Emission Control System Leak Detected (Very Small Leak) |
| P0444 | EVAP Purge Control Valve Circuit Open |
| P0445 | EVAP Purge Control Valve Circuit Shorted |
Fixing the Purge Valve Circuit
A P0443 code means the PCM found a fault in the purge valve circuit. Wiring, connectors and failed purge valves cause most cases.
- Find the purge valve and check the connector.
- Check power and the control signal.
- Measure the coil resistance.
- Check the wiring for opens and shorts.
Frequently Asked Questions
Where Is the Purge Valve?
On most vehicles, it is in the engine bay near the intake manifold, with two hoses and an electrical connector. Some vehicles mount it near the charcoal canister by the fuel tank. Your service manual shows the location.
Can I Drive with the P0443 Code?
Yes, in most cases. The engine runs normally, though EVAP purge may not work. Get it fixed before your next emissions test, and sooner if the engine is hard to start after refueling.
Can a Loose Gas Cap Set an EVAP Code?
Yes. A loose, damaged or wrong gas cap is one of the most common causes of EVAP leak codes. Tighten the cap until it clicks, or replace it if the seal is cracked. It can take several drives for the code to clear.
How Long Does It Take for an EVAP Code to Clear?
After a repair, the PCM must run its EVAP test again, which often needs a cold start, a fuel level between about a quarter and three quarters of a tank and certain driving conditions. It can take several days of normal driving.
Should I Top Off the Tank After the Pump Clicks Off?
No. Overfilling can push liquid fuel into the charcoal canister and damage it, which can lead to EVAP codes and a costly canister replacement. Stop at the first click.
Will an EVAP Code Fail an Emissions Test?
Yes, in most areas. An active EVAP code turns on the check engine light, which fails an OBD-II inspection. Clearing the code right before the test does not help either, because the EVAP monitor will show as not ready. Fix the fault, then drive normally until the monitors complete.
Can I Test the EVAP System Without a Smoke Machine?
You can do some checks without one. Inspect the gas cap, look over the hoses you can reach and test the purge and vent valves with a hand vacuum pump and a scan tool. Small leaks are very hard to see, though, so many owners pay a shop for a smoke test, which often costs less than one wrong part.