EVAP Purge Flow Incorrect
The engine's EVAP system is not purging properly, causing performance issues.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The computer checks for how much fuel vapor is being sucked out of the charcoal canister during an engine run and finds it's not what it expected, meaning something in the process isn't working right.
What the computer is actually seeing
The control module sees a fuel vapor flow rate during purging that is significantly lower than expected, usually less than 0.5 grams per second when it should be at least 1.0 grams per second.
What a healthy reading looks like
Expect a purge flow rate between 1.0 and 5.0 grams per second during peak efficiency; if it's below 1.0 grams per second, there's an issue.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect all vacuum hoses and connections in the EVAP system for cracks or disconnections. Fix any issues found. Decision: Are all hoses intact? Yes - go to step 2. No - repair hoses and retest.
- 22. Manually activate the purge valve using a scan tool. Monitor for flow through the EVAP system. Decision: Is there proper flow? Yes - go to step 3. No - replace the purge valve and retest.
- 33. Check the charcoal canister for blockages or saturation with fuel. Decision: Is the canister clean and functional? Yes - inspect fuel tank pressure sensor. No - replace the charcoal canister and retest.
- 44. Verify wiring and connectors leading to the purge valve and fuel tank pressure sensor for continuity and corrosion. Decision: Is wiring in good shape? Yes - go to step 5. No - repair wiring as needed and retest.
- 55. Test the fuel tank pressure sensor for correct operation; it should show values between -3 to 5 inHg during a vacuum test. Decision: Is the sensor working properly? Yes - further diagnosis may be needed. No - replace the sensor and retest.
Common causes
- Clogged or faulty purge valve
- Faulty charcoal canister
- Leaking vacuum lines in the EVAP system
- Faulty fuel tank pressure sensor
- Wiring harness issue to the purge valve
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
It's drivable but could lead to increased emissions and fuel economy issues, fix soon.
Will this code come back after clearing?
If the underlying issue isn't fixed, yes, the code will likely return.
Why does this pair with other codes like SPN 4425?
They are related to the same EVAP system functionality, indicating multiple potential issues.
Working a real vehicle right now?
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