P1399: Random Cylinder Misfire Detected (Honda)
Severity: medium
What it means: P1399 is Honda's code for a random misfire, when a cylinder briefly fails to burn its fuel and the engine stumbles. It's similar to the generic P0300, and Honda's computer can set it at smaller speed changes. On an automatic, a misfire under load can feel like the transmission slipping or jerking.
Safe to drive? Drive gently and get it checked soon. A flashing check engine light means a bad misfire that can damage the catalytic converter, so stop driving hard.
Common symptoms
- Check engine light, sometimes flashing
- Rough idle or stumbling
- Jerking under load that can feel like the transmission
Likely causes, ranked
- Worn spark plugs or bad ignition coilDIY
- Valve clearance out of specShop
- Clogged EGR passagesShop
- Fuel delivery or vacuum leak problemDIY or shop
Advertisement
Vehicle-specific notes
- 2001–2003 Acura CL: On Acurazine, a 2003 CL that jerked in second gear had misfire codes P0300, P0301, P0305 and P1399, not transmission codes. Read the full answer · Source
DIY or shop?
DIY for plugs and coils. Valve adjustment and EGR cleaning are usually shop jobs.
Before you replace parts
- Read all codes, including cylinder-specific misfire codes.
- Inspect spark plugs and swap coils to see if a misfire moves.
- Check for vacuum leaks.
- Ask a shop to check valve clearance and EGR passages if it continues.
Safety / mechanic note
Verify with a mechanic. A severe misfire can overheat the catalytic converter. A code points to a circuit or system, not always a specific part.
Advertisement