P0457: Evaporative emission system leak detected (fuel cap loose/off)
An OBD-II trouble code for a leak in the evaporative emission system of the kind a loose or missing fuel cap causes, as the code’s own name says.
How to read it
P0457 is one of the standard OBD-II trouble codes stored when the check engine light comes on. SAE J2012, the standard that defines the codes, names it “Evaporative Emission System Leak Detected (fuel cap loose/off)”; a Volkswagen service update gives the same name.
Also searched as: code P0457, P0457 code.
Code names follow SAE J2012. Manufacturers add codes of their own, and the same code can have several causes: the vehicle’s service information or a qualified mechanic can say what it means for a particular car.
What the monitor checks
The federal rule requires the system to detect vapour leaks in the evaporative system and an absence of purge air flow from it.
What the manual says to do
Ford’s F-150 manual says that if the indicator stays on, the vehicle should be serviced at the first available opportunity, and that continued driving with it on can mean higher emissions, lower fuel economy, rougher running and more costly repairs.
How the light goes out
Under the federal rule, the check engine light may go out once the fault has not come back during three trips in a row in which its monitor runs without finding it. The system may erase the stored code if the same code has not been registered again in at least 40 engine warm-up cycles.
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More OBD-II trouble codes
The same shape elsewhere
Browse symbols drawn with letters and numbers or squares and rectangles.
Sources
- SAE J2012: Diagnostic Trouble Code Definitions (2002), SAE J2012, April 2002 (technically equivalent to ISO/DIS 15031-6), SAE International; published by Public.Resource.Org on the Internet Archive, Appendix B (powertrain DTCs)
- Volkswagen update 23X1: ECM software update (July 2018), Update 23X1, Volkswagen Group of America; published by NHTSA, DTC description table
- 40 CFR 86.1806-05, On-board diagnostics (2012 edition), 40 CFR 86.1806-05, US Government Publishing Office (Code of Federal Regulations), § 86.1806-05(b) and (c)
- 2020 F-150 Owner's Manual, Ford Motor Company, Instrument Cluster; On-Board Diagnostics (OBD-II)
Researched, edited and approved by Rory Hansen before publishing. Last reviewed September 28, 2026. How we research
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