Generic OBD2 code · Ignition system or misfire

P0307: Cylinder 7 Misfire Detected

The engine computer detected that cylinder 7 is misfiring, meaning it is not burning its fuel properly.

CodeP0307

SystemIgnition system or misfire

Typical urgencyHigh

Can I keep driving?If the check engine light flashes, reduce load and get it checked. A severe misfire can damage the catalytic converter.

What does P0307 mean?

The ECM watches crankshaft speed to detect misfires. When cylinder 7 slows the crankshaft more than expected, it counts a misfire and, past a threshold, stores P0307. This code only appears on engines with at least 7 cylinders, such as V8 engines.

If P0207 (Cylinder 7 Injector Circuit) is stored at the same time, check the electrical circuit of the cylinder 7 fuel injector first, because an injector that does not fire also makes that cylinder misfire.

Common symptoms

Check engine light on or flashing
Rough idle or shaking
Loss of power or hesitation
Higher fuel use

Common causes

The causes below are the ones commonly seen with P0307. The actual cause can vary by vehicle, engine and mileage, so treat this list as a starting point, not a diagnosis.

A worn or fouled cylinder 7 spark plug, or a damaged plug wire or boot on that cylinder
A failing cylinder 7 ignition coil (on coil on plug engines each cylinder has its own coil)
A clogged, leaking or electrically faulty cylinder 7 fuel injector
An intake or vacuum leak close to cylinder 7, such as a leaking intake gasket at that port
Low fuel pressure or an EGR fault, which usually affect more than one cylinder
Low compression on cylinder 7 from a valve, ring or head gasket problem (less common)

What to check with a scanner

In the app, check whether the code is stored or pending and whether P0300 or other single cylinder misfire codes are present with it.
Read freeze frame data: rpm, load and engine temperature show when the misfire happened.
Where your car supports Mode 06, look at misfire counts for cylinder 7 and the other cylinders.
Watch short and long term fuel trim. A lean trim on one bank can point to a vacuum leak or fuel delivery problem.
Swap the cylinder 7 ignition coil with cylinder 8, clear the code and drive. If the code changes to P0308, the coil is at fault. If P0307 comes back, look at the plug, the injector and compression on cylinder 7.

How to read and clear P0307 with OBD Master Pro

Plug in your adapter. Connect a generic ELM327 (or ELM329) OBD2 adapter to the diagnostic port, usually under the dashboard on the driver's side. Bluetooth Classic, Bluetooth LE, Wi-Fi and USB OTG adapters are supported.
Switch the ignition on. Turn the key to ON or start the engine, depending on your car.
Connect in OBD Master Pro. Open the app, go to Connection and pick your adapter. Classic Bluetooth adapters connect from the Bluetooth tab, Bluetooth LE adapters from the BLE tab with no pairing needed. Use the generic OBD2 / EOBD profile or your car's brand profile.
Read the codes. Open the fault codes screen to see stored, pending and permanent codes. Confirm P0307 is listed and note any other codes, since they often explain the cause.
Check the details. Look at freeze frame data, Live data and, where your car supports it, Mode 06 test results (see the checks above).
Fix, then clear. After the repair, clear the codes to turn off the check engine light. Clearing also resets the emissions readiness monitors, so drive normally and check the readiness screen before any inspection. Permanent codes cannot be erased with a scan tool; they clear on their own once the car's self test passes.

Tip: you can also look up P0307 and other codes in the app's DTC search without connecting to a car. If your adapter will not connect, use Connection > Share connection log and email it to support. Many cheap ELM327 clones only handle basic engine OBD2, which is all you need for P0307.

When to see a mechanic

Get professional help if any of these apply:

The check engine light is flashing (reduce load and get it checked, as a flashing light warns of catalyst damage)
The engine shakes badly, loses power or stalls
Swapping the coil or plug did not move the misfire
A compression or leak down test is needed

If you are unsure, a qualified technician can confirm the cause with tests such as smoke testing, pressure testing or scope readings. Clearing a code does not repair the fault.

P0307 FAQ

Where is cylinder 7?

Cylinder numbering differs by manufacturer and engine layout. Check the service information for your engine before working on it.

Can I drive with P0307?

Only gently, and not if the check engine light is flashing. A heavy misfire can overheat the catalytic converter.

Should I swap the coil to test?

Swapping the coil or plug with another cylinder and seeing whether the misfire moves is a common first test.

Does P0307 mean only cylinder 7 is affected?

It means the misfire monitor counted misfires on cylinder 7. If several cylinders misfire, P0300 (random or multiple cylinder misfire) or other single cylinder codes may be stored as well, which points to a cause shared by all cylinders, such as fuel delivery or a vacuum leak.

Check P0307 on your own car

OBD Master Pro turns your Android phone and a generic ELM327 adapter into a code reader: read and clear codes, view freeze frame and live data, and check emissions readiness.

Sources

Published October 24, 2026. Updated October 24, 2026. This guide is general information for generic SAE codes. Always follow the service information for your specific vehicle.