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P2404 EVAP System
Evaporative Emission System Leak Detection Pump Sense Circuit Range/Performance
The control module has detected that the leak detection pump sense circuit signal is outside the expected range or does not respond as it should during testing. The sense circuit reports pump current or position back to the module.
🚗 Yes. This emissions fault does not affect how the vehicle drives, but it should be repaired to complete emissions readiness.
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🎯 Top Causes, Ranked by Likelihood
#1 Faulty leak detection pump $120-$300
A worn pump produces an incorrect sense signal during the leak test.
#2 Restricted or blocked EVAP line $50-$200
A pinched or clogged vapor line changes the pressure the pump senses.
#3 Wiring or connector fault $40-$200
High resistance in the sense circuit distorts the reported signal.
#4 Charcoal canister restriction $150-$400
A saturated or blocked canister prevents proper pump operation and sensing.
🩺 Common Symptoms Check engine light is on EVAP monitor fails to run to completion No drivability symptoms Possible fuel vapor smell if a leak is present 💰 Repair Cost: DIY vs Shop
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🔧 How to Diagnose P2404 1 Inspect EVAP hoses and lines for kinks, cracks, or blockage.
2 Check the pump connector and sense circuit wiring for corrosion or high resistance.
3 Perform a smoke test of the EVAP system to find restrictions or leaks.
4 Replace the leak detection pump if the sense signal remains out of range after wiring checks.
❓ Frequently Asked Questions What does the sense circuit do?
It reports pump current or pressure back to the computer so it can judge whether the EVAP system holds pressure without leaking.
Could a loose gas cap cause this?
A loose cap more often triggers a leak code, but a large leak can affect the pump sense reading. Check the cap first.
Do I need a smoke test?
A smoke test is the most reliable way to find EVAP restrictions and leaks that upset the sense signal.
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