P0443
Evaporative Emission Control System Leak Detected (small leak)
Powertrain Emission Controls EVAP system leak 🟡 Moderate — Fix within a week
💬
What This Actually Means
In plain language — no jargon

Your car's fuel vapor recovery system has a small leak that lets fuel fumes escape instead of being captured and burned. Think of it like a tiny hole in a sealed container—the system can't maintain proper pressure.

⚡
Symptoms You May Notice
3 known symptoms for this code
Check engine light illuminated
Slight fuel smell near fuel door or under vehicle
No noticeable drivability issues
🔬
Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the evaporative emission (EVAP) system's ability to hold pressure/vacuum using a fuel tank pressure sensor or leak detection pump. When pressure drops slower than expected or fails to build, the system detects a small leak below the major leak threshold.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Fuel Tank Pressure Hold Time Holds vacuum for specified duration Pressure drops faster than threshold (small leak detected)
System Pressure Differential Maintains 2–7 inches H₂O pressure Falls below minimum sustainable pressure
🔧
Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Fuel filler cap
Replace with OEM cap; a loose or damaged cap is the most common cause.
2
EVAP charcoal canister hoses
Inspect rubber hoses for cracks, splits, or loose connections and reconnect or replace as needed.
3
Charcoal canister purge valve
Check for stuck-open valve or cracked housing and replace if carbon buildup or damage is visible.