- Vehicles
- Cars
P0306
P0306 (generic OBD-II): cylinder 6 misfire detected
Risk level
High
Professional inspection is recommended.
Urgency
High
Quick answer
The engine computer counted failed combustion in cylinder 6, so your engine has at least 6 cylinders. If the engine light flashes, stop somewhere safe. If it stays on, read and photograph the codes without clearing them.
Safety first
Stop and check this first
- In a hybrid, the engine bay holds high-voltage parts: only a trained workshop should work on it.
- With P0306 and a flashing light, driving on can damage the catalytic converter; Honda says to stop away from flammable material.
Safe checks you can perform
- Flashing or steady light
- Code list and freeze frame
- Hybrid car: do not open up the engine bay
Leave these tasks to a qualified professional
- Do not attempt this professional task: Coil swap test on cylinder 6
- Do not attempt this professional task: If the misfire stays: injector, wiring and engine condition
- Do not attempt this professional task: Service bulletin and final verification
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Coil swap test on cylinder 6
What they doThe technician reads the fault memory, moves the cylinder 6 coil to another cylinder, recreates the freeze frame conditions and reads again.
They must show youboth fault memory readings (before and after) and which cylinder the misfire moved to.
In writingwhich part is replaced, which test points to it and its part number.
If the misfire stays: injector, wiring and engine condition
What they doIf the misfire stays on cylinder 6, the technician checks the connector and ground, the injector and, if those pass, the cylinder's mechanical condition with a compression or leak-down test.
They must show youeach test result on cylinder 6 against the other cylinders and the manufacturer's specification.
In writingwhich tests were done, their results and the cause found.
Service bulletin and final verification
What they doThe workshop searches bulletins for P0306 by VIN; after the repair it drives under the freeze frame conditions and confirms the cylinder 6 counter does not rise.
They must show youthe bulletin search by VIN and the counter reading after the drive.
In writingthe bulletin number applied or that none exists, and the final test conditions.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Flashing or steady light
- Who:
- you, watching the cluster with the engine running.
- How:
- watch the engine light while driving. A brief flash at key-on with the engine stopped does not count.
- Result that matters:
- whether it flashes with the engine turning.
- If it flashes:
- this confirms an active misfire that can damage the emission system. Honda says to stop where there are no flammable objects, switch off for at least 10 minutes and take the car to a dealer.
- If it stays on:
- note P0306 and book a visit. Steady does not mean fixed; it only rules out the most urgent case.
- Evidence to keep:
- a photo of the cluster, when it flashed or came on (cold, idle, uphill) and the date.
With a flashing light, do not keep driving to see whether it goes off.
Evidence: Nissan USA malfunction indicator light guide · Title 13, California Code Regulations, Section 1968.2, Malfunction and Diagnostic System Requirements (OBD II) · Honda 2020 HR-V Owner's Guide - Dashboard details (malfunction indicator lamp)
Code list and freeze frame
- Who:
- you, with a generic OBD-II reader and the car parked.
- How:
- read confirmed and pending codes. Save the P0306 freeze frame screen (engine speed, load, temperature, road speed) and clear nothing.
- Result that matters:
- whether P0306 is alone or comes with other misfire, mixture or fuel level codes.
- If there are other codes besides the misfire:
- Volkswagen says to fix those first, because they can be the origin.
- If P0306 is alone:
- this points to that cylinder; the workshop moves on to the swap test.
- Evidence to keep:
- a photo of every code and of the freeze frame.
Read the tool only with the car stopped. Clearing the codes also erases the freeze frame the workshop needs.
Evidence: Volkswagen TSB 2025089 engine misfire diagnostic aid · Title 13, California Code Regulations, Section 1968.2, Malfunction and Diagnostic System Requirements (OBD II)
Hybrid car: do not open up the engine bay
- Who:
- you, checking the owner's manual or the car's paperwork.
- How:
- find out whether your car is a hybrid. In hybrids the petrol engine sits next to high-voltage wiring, usually orange.
- Result that matters:
- whether the car has a hybrid system.
- If it is a hybrid:
- do not handle coils or connectors; only a workshop trained in high voltage should work on it.
- If it is not a hybrid:
- still do not remove coils yourself; the value is in the reader diagnosis and the workshop swap test.
- Evidence to keep:
- model, year, engine and whether it is a hybrid, to give to the workshop.
Evidence: Toyota T-SB-0148-19 Highlander HV P0301-P0306
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- Vehicles
- Brand
- OBD-II genérico
- Product type
- Cars
Known code variants
- P0306
- P0306 cylinder 6 misfire
- P0306 fallo de encendido cilindro 6
- P0306 OBD2
What it means
P0306 is the generic code for a misfire in cylinder 6. California's OBD II regulation requires cars to watch for misfire that can damage the catalyst or raise emissions, and to identify the specific cylinder when only one is affected. The code says where combustion fails, not why: Volkswagen notes many replaced coils were not the cause, and Toyota published an engine computer reprogramming plus coil replacement for one hybrid model.
Warnings and stop conditions
- Higheditorial warning
In a hybrid, the engine bay holds high-voltage parts: only a trained workshop should work on it.
Evidence: Toyota T-SB-0148-19 Highlander HV P0301-P0306
- Highsource verified
With P0306 and a flashing light, driving on can damage the catalytic converter; Honda says to stop away from flammable material.
Evidence: Title 13, California Code Regulations, Section 1968.2, Malfunction and Diagnostic System Requirements (OBD II) · Honda 2020 HR-V Owner's Guide - Dashboard details (malfunction indicator lamp)
Symptoms and causes
Probable causes · in order
- Cylinder 6 coil or spark plugPossible
It shows when the misfire follows the cylinder 6 coil to the cylinder the technician moves it to. If it does not move, the coil is not the cause.
Evidence: Volkswagen TSB 2025089 engine misfire diagnostic aid · Toyota T-SB-0148-19 Highlander HV P0301-P0306
- Installation, connector or groundPossible
Volkswagen lists badly installed coils, loose or damaged connections and circuit grounds. It fits a misfire that comes and goes or started after a recent repair.
Evidence: Volkswagen TSB 2025089 engine misfire diagnostic aid
- Fuel quality or very low levelPossible
Volkswagen links misfires to poor fuel and to a nearly empty tank. It fits when the code comes with a low fuel warning or after filling up somewhere new.
Evidence: Volkswagen TSB 2025089 engine misfire diagnostic aid
- Engine computer calibrationLess common
On the 2017 to 2019 Toyota Highlander hybrid, Toyota requires an engine computer reprogramming and a coil replacement for P0306. It only applies if a bulletin matches your model.
Evidence: Toyota T-SB-0148-19 Highlander HV P0301-P0306
Virtual technician
Does P0306 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Nissan USA malfunction indicator light guide
Nissan USA · official_doc
- 2
Volkswagen TSB 2025089 engine misfire diagnostic aid
Volkswagen Group of America · 2013 · service_bulletin
- 3
Toyota T-SB-0148-19 Highlander HV P0301-P0306
Toyota Motor Sales USA · 2019 · service_bulletin
- 4
California Air Resources Board · 2006 · official_doc
- 5
Honda 2020 HR-V Owner's Guide - Dashboard details (malfunction indicator lamp)
American Honda Motor Co. · 2020 · manual
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