Code
P0446
GWM
P — Powertrain
- Malfunction in the ventilation circuit of the fuel vapor outlet monitoring system
AI status
Completed
Completed
100%
Causes
- Open or short circuit in EVAP vent valve wiring or connector
- Faulty canister vent/vent control valve (solenoid)
- Blocked, kinked or disconnected EVAP lines or vent port
- Failed EVAP canister (charcoal) or internal contamination
- Blown fuse or poor power/ground to valve circuit
- Faulty ECM or intermittent ECU driver
Symptoms
- Malfunction Indicator Lamp (MIL) / Check Engine Light illuminated
- Failed EVAP readiness at emissions test
- Occasional fuel smell near the fuel tank or canister
- Difficulty completing evaporative system self-test; EVAP monitor not ready
- No noticeable drivability problems in many cases
What to check
- Read and record freeze frame and pending codes with a scan tool; verify P0446 is current
- Check vehicle service information for vent valve location and normal state (open/closed)
- Visually inspect wiring and connector at the vent valve for corrosion, damage or loose pins
- Verify fuel cap is tight and in good condition (rule out simple cause)
- Check related fuses and main grounds for continuity
- Measure vent valve coil resistance and compare to service spec
Signal parameters
- Vent valve coil resistance: typically in the low tens of ohms (commonly ~20–50 Ω) — consult model-specific spec
- Connector voltage with key ON: battery voltage on supply pin; control pin may be switched to ground or driven by PWM depending on design
- When commanded OPEN/CLOSE: scan tool should show state change and EVAP pressure sensor should respond (pressure change or vent to atmosphere)
- No continuity or infinite resistance indicates open coil; short to ground indicates internal short — both fault conditions
- Current draw when energized: should be within manufacturer specification (abnormally high or low suggests valve fault)
Diagnostic algorithm
- Retrieve freeze-frame data and confirm P0446 presence; clear codes and attempt to re-run EVAP monitor to reproduce.
- Inspect fuel cap and EVAP hoses for obvious leaks, damage or disconnection; repair as needed.
- Visually inspect vent valve connector and wiring for corrosion, bent pins, damage or water entry; repair wiring/connector issues.
- With ignition OFF, disconnect vent valve and measure coil resistance; compare to service spec (if out of range, replace valve).
- With connector connected, backprobe connector while commanding the valve ON/OFF with a scan tool; verify supply voltage and switching (ground or PWM).
- Apply bench battery voltage to the valve (if removable) to verify audible operation and correct movement; do not exceed vehicle specs.
- Perform a smoke or pressure decay test of the EVAP system to check for blockages at the canister vent or clogged hoses.
- Inspect charcoal canister for fuel saturation or internal damage if venting appears blocked; replace if contaminated.
- If wiring and valve operation are good, check ECM outputs and grounds for intermittent faults; consult wiring diagram and test/repair as required.
- After repairs, clear codes and verify EVAP monitor completes and P0446 does not return; road test and re-check readiness.
Likely causes
- Corroded/loose connector at vent valve
- Vent valve coil open or shorted
- Vacuum/pressure line blockage or collapsed hose
- Damaged charcoal canister preventing venting
- Bad ground or supply to vent valve
- Intermittent fault caused by water intrusion or wiring chafe
Fault status
Status
P0446 — Malfunction in the ventilation circuit of the fuel vapor outlet monitoring system. The ECM detected an improper signal or circuit fault in the EVAP canister vent control/vent valve or its wiring, preventing expected vent control or EVAP system monitoring.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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