LOW TO MODERATE System: EVAP Emissions System SAE J2012 Standard

P0446: Evaporative Emission System Vent Control Circuit Malfunction

The ECM detects an electrical circuit failure (open circuit, short to ground, or high resistance) in the EVAP canister vent valve solenoid wiring or internal coil winding.

Driveability & Safety Advisory

Yes, safe to drive. Engine performance is unaffected.

Official Manufacturer TSB Advisories

GM 02-06-04-037 Target: 2003–2010 Chevrolet Tahoe / Suburban

Factory Condition: Wiring harness harness chafe at rear frame crossmember cuts 12V power supply to vent solenoid.

OEM Service Remedy: Repair wire loom near rear shock tower; install revised weather-pack connector.

Physical Component Location & Service Access

Mounted on or directly next to the charcoal canister under the vehicle near the spare tire or fuel tank.

Electrical Specifications & Live PID Benchmarks

Scan Tool Live Data Targets

Vent Valve Commanded State: ON / OFF response verified on scan tool

Digital Multimeter (DMM) Specs

Vent Solenoid Resistance (Pins 1-2): 15.0 – 25.0 Ohms (Infinite = Open circuit)
Vent Valve Supply Voltage: 12.0V – 14.0V battery voltage
Control Wire Voltage (when commanded ON by scan tool): < 0.3V (solid ground from ECM)

Documented Model-Specific Case Studies

2005–2011 Toyota Corolla

Root Cause: Corrosion in rear vent valve sub-harness connector.

Verified Fix: Solder new weather-pack pigtail connector.

Technician Inspection & Testing Workflow

1

Disconnect 2-pin connector at vent solenoid. Check for 12V with key ON.

2

Check ground side: Use test light to battery positive and command vent valve ON with scan tool.

3

Measure coil resistance with multimeter (should be ~20Ω).

Cost Breakdown

DIY Replacement Parts: $25 – $65
Independent Repair Shop (Parts + Labor): $150 – $300
Standard Diagnostic Time: 1.0 – 2.0 Flat-Rate Hours

Tools & Parts Matrix

Recommended Parts: EVAP Vent solenoid valve, Wiring pigtail harness
Required Test Tools: Digital multimeter, 12V test light, Scan tool

Diagnostic Questions & Answers

Why does my gas pump nozzle keep clicking off when filling gas?

When code P0446 is active, the vent valve may be stuck closed, preventing air inside the fuel tank from venting out while fuel is pumped in.