Code
P0446
HUMMER
P — Powertrain
EVAP Vent Solenoid Valve Control System
Views:
UK: 21
EN: 41
RU: 62
AI status
Completed
Completed
100%
Causes
- Open or short in vent solenoid wiring or connector
- Failed EVAP vent/vent solenoid (stuck open or closed)
- Faulty PCM or EVAP control module
- Poor electrical ground or corrosion at connector
- Restricted or clogged vent valve or charcoal canister
- Recent fuel system service or improper reassembly
Symptoms
- Check Engine Light (MIL) illuminated
- EVAP system readiness test incomplete or failed
- Fuel odor near the rear of the vehicle (evap canister area)
- Difficulty passing emissions test
- Possible occasional hard starts or rough running after refueling (less common)
What to check
- Retrieve freeze frame and enhanced data with a scan tool; record EVAP vent command and status
- Visually inspect vent solenoid, wiring harness, and connectors for damage or corrosion
- Check for TSBs/recalls related to EVAP vent solenoid on the specific HUMMER model and year
- Perform a wiggle test of wiring while monitoring live data or DTC status
- Measure voltage at the vent solenoid connector while commanding the valve ON and OFF
- Measure coil resistance of the vent solenoid and compare to specification
Signal parameters
- Typical supply voltage at the vent solenoid harness: ~12 V (key ON) — confirm with service data
- PCM switching signal: ground-side switching or PWM command when vent is operated; varies by model
- Expected coil resistance (typical): 15–60 ohms (consult factory spec for exact value)
- When commanded closed/open by PCM, solenoid circuit voltage should change accordingly and show continuity to ground when activated
Diagnostic algorithm
- Clear any stored codes and confirm P0446 returns. Capture freeze-frame and live EVAP vent status with scan tool.
- Perform a careful visual inspection of vent solenoid, connector and wiring harness for damage, abrasion, or corrosion. Repair or replace as needed.
- Unplug the vent solenoid and check for terminal corrosion. Backprobe the connector and measure supply voltage with key ON. Compare to expected battery voltage.
- Command the vent solenoid ON and OFF using a scan tool while monitoring the harness voltage/ground. Verify PCM is commanding the circuit.
- Measure the solenoid coil resistance with an ohmmeter. If open or out of spec, replace solenoid.
- If wiring and solenoid test good but command is missing, check for an intermittent ground, fuses, or related relay and verify PCM output driver. Test continuity between PCM and solenoid connector.
- Perform an EVAP smoke test to ensure the vent mechanism and canister are not mechanically stuck or clogged.
- If wiring, connector and solenoid are good but fault persists, consider PCM or EVAP control module failure and follow manufacturer procedures for module testing or replacement.
- After repairs, erase codes and perform drive cycle to confirm the system is operating and the code does not return.
Likely causes
- Damaged wiring harness to the EVAP vent solenoid
- Corroded or water-intruded connector at the vent solenoid
- Defective vent solenoid coil (no continuity or intermittent)
- Contaminated or mechanically stuck vent valve
- PCM not commanding or not sensing the circuit correctly
Fault status
Status
EVAP Vent Solenoid Valve Control Circuit Malfunction (P0446): The vent/vent valve circuit is not responding within expected parameters.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
Similar codes
HTML Workshop Manuals AI manual library for HUMMER Click to show available manuals 77
HUMMER 2010 H3 Alpha
HTML ManualHUMMER 2010 H3 Base, Standard
HTML ManualHUMMER 2010 H3 Base, Automatic
HTML ManualHUMMER 2010 H3T Alpha
HTML ManualHUMMER 2010 H3T Base, Standard
HTML ManualHUMMER 2010 H3T Base, Automatic
HTML ManualHUMMER 2009 H2 4D Utility Wagon
HTML ManualHUMMER 2009 H2 4D Utility Pickup
HTML ManualYour experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email