P0307

Cylinder 7 Misfire Detected

P0307 is a generic OBD-II powertrain diagnostic trouble code: Cylinder 7 Misfire Detected. It is logged by the engine control unit when the misfire monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P0307
Group
Powertrain
System
Misfire
Severity
Warning (MIL on, possible limp mode)
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What P0307 means

P0307 is an SAE generic powertrain code that means "Cylinder 7 Misfire Detected." The powertrain control module (PCM) continuously monitors crankshaft rotational velocity via the crankshaft and camshaft position sensors. When cylinder 7 fails to fire correctly, the crankshaft momentarily decelerates; if the PCM detects this variation exceeding a calibrated threshold, it stores P0307 and illuminates the MIL.

Misfires in a single cylinder are most commonly caused by ignition system failures (spark plug, coil, or high-voltage wiring), a stuck-open or clogged fuel injector, or a loss of cylinder compression due to a burnt exhaust valve or leaking head gasket. A flashing MIL indicates an active, continuous misfire severe enough to damage the catalytic converter within seconds.

Diagnosis should always start by swapping ignition components (coil and spark plug) between cylinder 7 and a known-good cylinder to confirm or rule out ignition causes before moving on to fuel delivery and mechanical compression testing.

Common causes

Most-frequently reported root causes when P0307 is logged.

  • 1
    Faulty or worn spark plug on cylinder 7
  • 2
    Failed or failing ignition coil on cylinder 7
  • 3
    Damaged, shorted, or open wiring/connector to cylinder 7 coil or injector
  • 4
    Clogged or leaking fuel injector on cylinder 7
  • 5
    Low engine compression on cylinder 7 (burnt valve, worn rings)
  • 6
    Leaking head gasket allowing coolant or combustion gas crossover
  • 7
    Vacuum leak in the intake tract near cylinder 7
  • 8
    Faulty crankshaft or camshaft position sensor providing incorrect timing data

Symptoms drivers notice

MIL (Check Engine Light) illuminated, possibly flashing during active misfire
Rough idle or noticeable engine vibration, especially at low RPM
Hesitation or stumble during acceleration
Reduced engine power and decreased fuel economy
Fuel smell from the exhaust due to unburned hydrocarbons
Engine may enter limp/reduced-power mode if misfire is severe or persistent

How to diagnose P0307

A typical diagnostic flow when this code is present.

  1. 1
    Connect an OBD-II scanner and record all stored codes and freeze-frame data
  2. 2
    Inspect cylinder 7 spark plug
  3. 3
    Swap the cylinder 7 ignition coil with a coil from a known-good cylinder and re-test
  4. 4
    Check cylinder 7 injector wiring connector and resistance
  5. 5
    Perform a fuel pressure test to confirm the rail is within spec
  6. 6
    Conduct a compression test on cylinder 7
  7. 7
    Monitor coolant level and look for white exhaust smoke or milky oil as indicators of head gasket failure

Related powertrain codes

Frequently asked questions

Can I drive with a P0307 code?

Short distances at reduced speed may be acceptable if the MIL is steady, but driving with a flashing MIL risks destroying the catalytic converter within minutes.

Why does P0307 only apply to engines with 7 or more cylinders?

P0307 only appears on V8, V10, V12, or inline-8+ engines where a physical cylinder 7 exists in the firing order.

What is the most common fix for P0307?

On high-mileage vehicles the most frequent repair is replacing the spark plug and/or ignition coil on cylinder 7.

Could a bad crankshaft position sensor trigger P0307 instead of a random-misfire code like P0300?

A failing crank sensor typically causes P0300 or a no-start condition rather than a single-cylinder code.

Disabling P0307 in software

RaceTune can permanently disable P0307 — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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