Skip to content
Skip to content

OBD-II Code

P1399

Severity

Not yet reviewed

Nobody on our side has assessed this code yet, so we are not going to guess at how serious it is.

Can you drive it

We cannot say

Treat it as unknown until a shop reads it with live data. If the check-engine light is FLASHING, stop driving as soon as it is safe to — that means an active misfire, whatever the code.

Indicative cost (USD)

$80–$2,400

From this code's diagnostic notes. Varies by vehicle, diagnosis, parts, and local labor. This is not a repair quote.

$80 (plug set DIY) to $2,400 (full VCM rocker-arm repair).

P1399 on a Honda is a random-misfire code — Honda's manufacturer-specific equivalent of OBD-II's generic P0300, set when the ECM detects misfires across multiple cylinders without isolating a single offender.

How a shop works this

Work from evidence to part, not the other way round. A code names a circuit or a symptom; it does not name the part that failed.

  1. Note every code that is set, not just this one.

    Codes that appear together usually narrow the cause faster than any one of them read alone.

  2. Read the freeze frame — the conditions the fault was recorded under.

    Cold or warm, idle or load, road speed and engine speed. A fault that only appears cold is a different fault from one that only appears under load, even with the same code on the scanner.

  3. Confirm the fault is current rather than history.

    Clear the code and see whether it returns under those same conditions. A code that does not come back may have been logged during a repair, a flat battery, or a bad connection that has since been disturbed.

  4. Then follow the diagnostic notes further down this page, in the order they are written.

    They are written in the order a shop works this code, cheapest checks first. Where they name a component, inspect its wiring and connector before replacing it.

If the code comes back after a repair, the underlying fault is still there. That is the point to bring in a scanner with live data and freeze-frame, or a shop that has one.

Common symptoms

  • Check engine light
Read the full diagnostic procedureP1399 on a Honda is a random-misfire code — Honda's manufacturer-specific equivalent of OBD-II's generic P0300, set when the ECM detects misfires acr…

P1399 on a Honda is a random-misfire code — Honda's manufacturer-specific equivalent of OBD-II's generic P0300, set when the ECM detects misfires across multiple cylinders without isolating a single offender. The ECM watches crankshaft deceleration events per firing event and flags any cylinder whose deceleration deviates from the expected window; when the deviation is spread across multiple cylinders rather than concentrated on one, P1399 sets instead of P0301-P0306.

Cheapest-first ladder

  1. scan fuel trims first — STFT and LTFT both pinned above +15% on both banks means vacuum leak or low fuel pressure (lean random misfire); both pinned below -10% means rich condition (failing pressure regulator, leaking injector, or stuck-open EVAP purge).
  2. Pull all plugs and read them as a set — uniform light-tan = good, uniform black/sooty = rich/cold, mixed colors with one or two outliers = the outliers are your real problem and you should be chasing a cylinder-specific code that hasn't matured yet.
  3. Smoke-test the intake for vacuum leaks.
  4. Check fuel pressure with a mechanical gauge (J-series V6 targets 47-54 psi at idle; K-series 4-cylinder targets 50-57 psi).
  5. Don't replace ignition coils as a set before checking the VCM cylinder-deactivation system on V6 Accords / Odysseys / Pilots — Honda's Variable Cylinder Management (VCM) sticks rocker arms in the deactivated state and produces a textbook P1399 random misfire on 3 cylinders at once when the engine tries to reactivate them.
Vehicle-specific patterns2008-2017 Accord V6 (J35), 2005-2017 Odyssey 3.5L (J35), and 2009-2015 Pilot 3.5L (J35) are the kings of P1399 — Honda's VCM (Variable Cylinder Manag…
  • 2008-2017Accord V6 (J35), 2005-2017 Odyssey 3.5L (J35), and 2009-2015 Pilot 3.5L (J35) are the kings of P1399 — Honda's VCM (Variable Cylinder Management) cylinder-deactivation system sticks rocker arms in deactivated mode and causes random misfires on 3 cylinders simultaneously when the engine commands reactivation. The shop ladder for VCM-equipped J35s: change the ATF and engine oil first (the VCM solenoid is oil-pressure-actuated and dirty oil sticks the rocker arms), replace iridium spark plugs at 60k intervals, swap aging ignition coils as a set, and inspect/adjust valve clearances (Honda specs 0.008-0.010 inch intake, 0.011-0.013 inch exhaust on most J35 variants) — Honda issued multiple TSBs covering aftermarket VCM-disable modules and rocker-arm replacement.
  • 2002-2006CR-V 2.4L (K24A1) and 2003-2007 Accord 2.4L (K24A4) throws P1399 from EGR-passage carbon buildup that intermittently floods random cylinders with exhaust gas — walnut blast the intake.
  • 2006-2011Civic 1.8L (R18) throws P1399 from worn iridium plugs past 80k miles and from carbon-fouled intake valves on the SOHC i-VTEC head.

Estimated repair$80 (plug set DIY) to $2,400 (full VCM rocker-arm repair).

Look up another code

More free tools

VIN DecoderDecode year, make, model, engine, recalls.Maintenance ScheduleOil, timing belt, fluids, by vehicle.Tire SizeOEM vs new — diameter delta + speedo error.Gas CostWeekly, monthly, annual fuel math.

See all 9 tools