P0442 on a 2016 GMC Canyon
P0442 means the EVAP system could not hold pressure or vacuum during a leak test, but the leak is small.
Not your vehicle? See general P0442 info.
Most common causes on the 2016 GMC Canyon
Ranked from 267 NHTSA owner complaints filed for this vehicle.
- 1
Chafed fuel line / leak near fuel tank (missing skid plate or AC-line contact)
High severityFuel leaking from a hose rubbing on the AC line and from a tank missing its protective skid plate both breach the sealed fuel system near the EVAP components.
Reported in 2 NHTSA complaints - 2
Rodent-damaged fuel line
High severitySoy-based line coating attracts wildlife on this truck; a chewed-through fuel line breaches the sealed fuel system that the EVAP monitor is testing.
Reported in 1 NHTSA complaintParts:fuel line - 3
Loose or damaged gas cap
Low severityThe most common trigger for a small EVAP leak code; check the cap seal before anything else.
Common causeParts:fuel filler cap - 4
EVAP purge valve failure
Medium severityA stuck or leaking purge solenoid prevents the system from sealing during the self-test.
Common causeParts:purge valve - 5
Cracked EVAP canister or vent valve
Medium severityAge-related cracking is a common small-leak source; a smoke test will pinpoint it.
Common cause - 6
Cracked or pinched EVAP vapor hose
Medium severityLines routed near hot or moving components can crack or get pinched, producing a small leak.
Common causeParts:EVAP vapor hose
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These causes are aggregated from NHTSA owner complaints and general repair knowledge — this is not a diagnosis. P0442 on your car still needs shop confirmation before any repair.
Common symptoms
- Check engine light
- Fuel smell near vehicle
- Usually drives normally
- Hard start after fueling in some cases
What to check before replacing parts
Tighten and inspect the gas cap
Look for: A cap that doesn't click to full tightness, has a visibly cracked or flattened seal, or is simply missing is the single most common cause of a small EVAP leak — rule it out first.
Smoke-test the EVAP system
Look for: Because this is a small leak, expect only a thin wisp of smoke or a faint hiss at one spot (a hose, seam, or valve) rather than an obvious cloud — look closely and take your time.
Check purge valve sealing
Look for: A purge valve that doesn't hold vacuum when commanded closed lets a small amount of air bleed through, which the system reads as a leak during its self-test.
Inspect hoses near the tank and engine bay
Look for: Look for small cracks, soft/collapsed spots, or a hose that has pulled loose slightly at a fitting — any of these can leak just enough to trip a small-leak code without an obvious fuel smell.
Verify vent valve operation
Look for: A vent valve that doesn't seal fully when commanded closed prevents the system from holding vacuum during its self-test, which reads as a small leak even with no physical leak in the hoses.
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