OBD-II Code · Misfire
P0499
Powertrain Diagnostic Code (P0499)
See deep dive below for full diagnostic context.
Common symptoms
- CEL
Likely causes
- See deep dive
Where to start
- Try the cheapest cause first. Start by checking: see deep dive.
- Cost & scope. $50-$2,000
- If the code returns after the fix: escalate to a shop or scanner with live-data and freeze-frame. A code that re-sets means the underlying fault is still there.
Read the full diagnostic procedure
P0499 reports the EVAP vent valve control circuit voltage is high, meaning the circuit is open or shorted to power and the PCM cannot command the vent valve through its normal range. Cheapest diagnostic: confirm the vent valve is plugged in, then measure resistance across the valve terminals expecting 20-30 ohms on most platforms; an infinite reading confirms an open winding. Probe the harness at the connector with key on: you should see roughly 12V on the supply pin from the PCM, and the control pin should pulse to ground when the vent valve is commanded closed during EVAP testing. The expensive misdiagnosis is replacing the canister assembly when the fault is a $50 vent valve, a $5 connector repair, or a pinched harness from a recent suspension job.
Vehicle-specific patterns
Vehicle-specific patterns: 2003-2011 Honda Pilot/Odyssey/Ridgeline CVSV fails open from internal salt corrosion in northeast and midwest states; 2007-2013 Toyota Camry/Sienna VSV diaphragm tears at the vent valve, producing intermittent P0499; 2008-2014 Subaru Outback/Forester vent valve harness gets pulled apart at the rear subframe during suspension service; 2009-2015 Ford Flex/Taurus 3.5L vent valve connector backs out at the rear of the canister (TSB 14-0007). Estimated repair: $110 to $440.
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