Code
P0447
HUMMER
P — Powertrain
Evaporative Emission Control System Vent Control Circuit Open
Views:
UK: 19
EN: 33
RU: 42
AI status
Completed
Completed
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Causes
- Open or broken wiring in the vent valve/solenoid circuit
- Disconnected, corroded or damaged connector at the vent valve
- Failed EVAP vent valve / canister purge vent solenoid
- Blown fuse or poor power/ground supply to the circuit
- Faulty PCM / module output (rare)
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Failed EVAP system readiness or emissions test
- Possible fuel odor near EVAP canister area (if valve physically stuck)
- EVAP system leak/vent test failures
- Usually no effect on engine driveability
What to check
- Read DTCs and freeze frame with a scan tool; note related EVAP codes
- Visual inspection of vent valve, harness, and connector for damage or corrosion
- Backprobe vent valve connector to check supply voltage and ground/command signal
- Measure vent valve coil resistance with multimeter (solenoid unplugged)
- Check continuity between vent valve connector and PCM pin; inspect grounds
- Verify fuses and relays for EVAP circuit
Signal parameters
- Supply voltage at vent valve: approximately battery voltage (~11–14 V) with ignition ON (depends on vehicle)
- Control signal: PCM switches the circuit (ground or switched voltage) — should toggle when commanded by scan tool
- Typical vent valve coil resistance: consult service data; commonly in the low tens of ohms (example 20–40 Ω) — check factory spec
- Open-circuit detection: infinite or very high resistance at vent valve indicates open
- Short-to-ground/short-to-voltage will show low resistance or near-battery voltage continuously
Diagnostic algorithm
- Retrieve DTCs and related codes; record freeze frame data. If other EVAP codes exist, address them in combination.
- Perform a visual inspection of the EVAP vent valve, vacuum lines, harness and connector for damage, corrosion or disconnection.
- With ignition OFF, unplug vent valve connector and measure coil resistance across the valve terminals. Compare to factory spec. An open (OL) reading indicates a failed solenoid.
- With connector still disconnected, turn ignition ON (engine OFF) and measure voltage at the harness power terminal. Verify battery voltage is present where expected.
- Reconnect and backprobe the control terminal. Use a scan tool to command the vent valve ON/OFF while monitoring the control line for switching (voltage change or ground switching).
- If no switching, check continuity from the PCM control pin to the vent valve connector; inspect for open circuits or high resistance.
- Check relevant fuses and grounds. Wiggle wiring while monitoring to find intermittent opens.
- If wiring and connector are good but no proper control signal from PCM, consider replacing the vent valve. If problem persists with new valve and confirmed wiring, suspect PCM driver fault and follow manufacturer procedures before replacing PCM.
- After repairs, clear codes, perform active tests and an EVAP system leak/functional test or smoke test to confirm proper operation and readiness.
Likely causes
- Connector pushed out or pins corroded at vent valve
- Wire chafed or broken between vent valve and PCM
- Vent valve coil failed (open circuit)
- Inline fuse for EVAP circuit blown
- PCM driver circuit open or internal fault
Fault status
Status
PCM detected an open circuit in the EVAP vent control (vent valve/solenoid) wiring — circuit not responding to control commands.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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