Evaporative Emissions System Leak Detection Pump Performance
The evap leak detection pump isn’t performing as expected.
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What it means (plain English)
The computer is checking the system that finds leaks in the evaporation emissions and it sees something not working right with the leak detection pump.
What the computer is actually seeing
The engine control module (ECM) expects the leak detection pump to create a specific pressure drop within the evap system when activated, typically around 1-3 inches of water column vacuum. If it fails to do so within a certain time frame, it triggers this code.
What a healthy reading looks like
Pressure in the evaporative emissions system during the leak check should drop 1-3 inches of water column vacuum in under 10 seconds.
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 the wiring and connector to the leak detection pump for damage or corrosion. Decision point: Is the wiring intact?
- 22. Check the evap system lines for blockages or leaks. Use a smoke tester if necessary. Decision point: Are the lines clear?
- 33. Activate the leak detection pump using a scan tool and monitor the pressure drop in the system. Decision point: Is the expected pressure drop achieved?
- 44. If the pump doesn’t activate, check for power and ground at the pump connector. Decision point: Is power and ground present?
- 55. If no issues are found, consider replacing the leak detection pump and recheck the system. Decision point: Did the code return after replacement?
Common causes
- Faulty leak detection pump
- Clogged evap system lines
- Damaged wiring or connectors
- Faulty ECM
- Software glitch
Typical repair cost
$$
Related codes
Frequently asked questions
Is it safe to drive with this code?
Yes, but it may impact emissions and fuel efficiency.
Will this code come back after clearing?
It can if the underlying issue isn’t fixed.
Why does this code appear with P0456 or P0455?
These codes relate to the evap system and often indicate similar problems.
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