P0499
PowertrainEvap Systemmoderate severityEvaporative Emission System Vent Valve Control Circuit High
What P0499 Means
The PCM detects high voltage in the EVAP vent valve control circuit. This may keep the vent valve from sealing during leak diagnostics.
Symptoms
- Check engine light on
- Failed EVAP monitor
- No noticeable driving symptoms
Common Causes
- Open circuit in vent valve wiring
- Faulty vent valve solenoid
- Corroded or loose connector
- Faulty PCM driver circuit
Diagnostic Steps
- Scan and record freeze frame data
- Inspect vent valve wiring for opens
- Measure vent valve circuit voltage
- Test vent valve solenoid resistance
🔌 Don't have a code reader?
Any of these will read and clear this code — pick by how deep you want to go.
Budget handheld~$40
ANCEL AD410 →
No-phone-needed handheld — reads, clears, live data, freeze frame.
✓ ANCEL official store
Serious DIY~$100
BlueDriver Pro →
Enhanced codes (ABS, airbag, TPMS) plus repair reports.
SHOP FAVORITEShop-grade tablet~$300
Autel MaxiCOM MK808S →
Bidirectional tests, service resets, all systems.
✓ Autel official store
Pro diagnostics$1,500+
Autel MaxiSys MS906 Pro →
Full-system pro platform — topology mapping, ECU coding, the works.
✓ Autel official store
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