Evaporative emission system loose fuel cap
P0457 — Evaporative emission system loose fuel cap
System: Powertrain | Type: Generic (OBD-II Standard) | Make: Generic
P0457 is a generic (obd-ii standard) powertrain diagnostic trouble code. It belongs to the P-prefix family of codes, which covers engine, transmission, emissions, or fuel-system faults.
Scanning & clearing: A generic OBD-II scan tool will usually read and clear powertrain (P) codes. For live data, freeze-frame capture, and bi-directional tests you may need a more capable scan tool that supports the vehicle's ECM protocol.
Because P0457 is a generic OBD-II code, its base definition is shared across manufacturers. The specific diagnostic steps, reference values, and repair procedures can vary by vehicle, and the TaT Diagnostic Assistant includes verified procedures submitted by working technicians.
The ECM sets P0457 when it detects a significant pressure loss in the EVAP system, specifically indicating that the fuel cap is loose, not sealing properly, or missing. This prevents the system from maintaining the necessary vacuum or pressure during self-diagnostics, leading to fuel vapour leakage.
Detailed possible causes for P0457 are available to TaT members.
Unlock with Free TrialStep-by-step diagnostic guidance for P0457 is available to TaT members. Our Diagnostic Assistant provides professional-level troubleshooting procedures written by experienced technicians.
Unlock with Free Trial| Code | P0457 |
| System | Powertrain |
| Type | Generic (OBD-II Standard) |
| Make | Generic |
| Causes | Available |
| Diag. Assistant | Available |
| Video | — |
Get complete diagnostic info, causes, and repair guidance.
Start Free 7-Day Trial Member LoginSearch all 8,602 fault codes with complete diagnostic details, possible causes, and repair guidance.
Start Your Free 7-Day Trial Member Login© 2026 The Automotive Technician (TaT) — www.tat.net.au