Honda P1399: Random Misfire — Fix
On Honda vehicles, P1399 means a random/multiple-cylinder misfire detected by the Honda ECM — combustion is failing across cylinders.
- Applies to
- Honda vehicles
- Est. repair cost
- $40 – $800
- Time to fix
- 30 minutes – 2 hours
What it means
Causes include worn plugs, failing coils, fuel-delivery problems, vacuum leaks, or low compression. P1xxx codes are manufacturer-specific — P1399 is defined by Honda (not part of the generic SAE J2012 set), so this definition applies to Honda vehicles. Model years can vary, so confirm against the Honda service manual. Fix the fault, then clear the code with a scan tool.
Symptoms
- Check engine light (may flash)
- Rough idle and shaking
- Hesitation and power loss
How to fix it
- 1
Check ignition and fuel
1. Inspect spark plugs and coils. 2. Check fuel delivery and for vacuum leaks.
- 2
Diagnose deeper if needed
1. If ignition/fuel are good, check compression. 2. Repair, then clear the code.
Frequently asked questions
Is P1399 the Honda version of P0300?
Yes — it's Honda's random-misfire code, very similar to the generic P0300. Start with plugs, coils, and fuel.
Last updated July 19, 2026
Guidance only — always consult a qualified professional or the official service manual before carrying out repairs.