OBD-II Diagnostic Trouble Code
P0307 — Cylinder 7 Misfire Detected
P0307 means the ECM detected misfires on cylinder 7 by measuring a drop in crankshaft acceleration during that cylinder's power stroke. It only applies to engines with seven or more cylinders, mainly V8 gas and V8 diesel medium-duty trucks and V10 gas engines; inline-6 heavy diesels cannot set it.
Severity 4/5
Truck-relevant
Stop within 50 mi
Severity
Stop within 50 mi
Cylinder 7 Misfire Detected
Code
P0307
Category
Powertrain
Subsystem
Ignition
Truck-relevant
Yes
What this means for truckers
Cylinder 7 Misfire — same.
Before you replace parts — try this first
P0307 on the Ignition system is most often failed ignition coil or worn spark plug on cylinder 7 (gas engines) — not a dead part. On commercial diesels especially, work these in order before spending money on parts:
- Confirm the symptoms. Match what your truck is doing to the Symptoms section below. If the code is set but the symptoms are not there, clear the code and re-test after a drive cycle — it may not return.
- Clean and dry the sensor connector. Water, road salt, or oil seeping into a connector is the #1 fake sensor failure. Disconnect, look for green corrosion or moisture, spray with electrical contact cleaner, dry, reseat. Many faults clear here for $0.
- Inspect the wiring harness. Trace the wire from the sensor toward the ECM — look for chafing against the engine block, melted insulation near the turbo or exhaust, or pinch points where a clamp has rubbed through.
- Test the sensor before swapping it. Most Common Causes (below) list the expected voltage or resistance range — a $20 multimeter saves a $300 sensor swap that does not fix the problem.
- Only then, replace the part. Use the OEM or a tier-1 aftermarket. Cheap sensors throw the same code in two weeks.
Symptoms
Rough idle and a noticeable shake under load, check-engine light that may flash on gas engines when the misfire is severe enough to damage the catalyst, loss of power, and higher fuel use. On a diesel V8 you may see white or gray smoke at startup and a knock from the affected cylinder. Some engines cut fuel to the cylinder or limit power to protect the aftertreatment.
Common causes
- CommonFailed ignition coil or worn spark plug on cylinder 7 (gas engines) ($120–$400)
- CommonLeaking, stuck or poorly balanced fuel injector on cylinder 7 ($350–$1400)
- OccasionalDamaged coil or injector harness or connector for cylinder 7 ($100–$450)
- OccasionalLow compression on cylinder 7 from a burnt valve, worn rings or head gasket leak ($1500–$6000)
- RareVacuum leak at the intake runner near cylinder 7 (gas engines) ($150–$600)
How to fix
Swap the cylinder 7 coil (and plug) with another cylinder and see if the misfire follows it
When to use: Gas engines, as the first quick check
Run a cylinder contribution or injector balance test with a scan tool and replace the injector if cylinder 7 is out of range
When to use: Diesel engines or when the coil and plug test good
Inspect and test the cylinder 7 injector or coil wiring and connector for chafing, oil intrusion and resistance
When to use: When the misfire comes and goes or changes with harness movement
Do a compression or cylinder leak-down test on cylinder 7
When to use: When ignition and fuel delivery check out but the misfire stays
Affects most
- Ford F-3501 complaint mention this code
Related
- → Browse all DTC trouble codes
- → Decode a VIN to check codes for your truck
- → Owner-operator maintenance guides
- → P0300 — Random/Multiple Cylinder Misfire Detected
- → P0301 — Cylinder 1 Misfire Detected
- → P0302 — Cylinder 2 Misfire Detected
- → P0303 — Cylinder 3 Misfire Detected
- → P0304 — Cylinder 4 Misfire Detected
- → Complaints on Ford F-350
Frequently Asked Questions
Can I drive with code P0307?
Drive with caution. P0307 is severity 4 — stop within ~50 miles. Most commercial diesel codes at this severity (turbo, fuel rail, transmission solenoid) can damage adjacent expensive components if left unrepaired. Get to a service location before highway-speed loads.
How much does it cost to fix P0307 on a commercial truck?
Total repair cost ranges $100–$6000 depending on the root cause. The cheapest fix is usually the first one listed below — Failed ignition coil or worn spark plug on cylinder 7 (gas engines) — which is also the most common. On commercial trucks the cost is usually higher than passenger vehicles due to part availability and shop labor rates ($120–185/hour at most truck shops, vs $90–130 at general auto shops). DIY-capable fixes (sensors, hoses, filters) are at the low end; major component replacements (turbo actuator, high-pressure fuel pump, transmission solenoid pack) are at the high end. Always diagnose with a scan tool BEFORE replacing parts — guessing wrong on a $1,500 turbo actuator when the actual issue was a $30 boost hose is a common expensive mistake.
Will P0307 fail a DOT inspection?
P0307 is generally not a direct DOT inspection fail item by itself. Inspectors focus on safety-critical systems (brakes, steering, tires, lights, hours-of-service). However, the check engine light alone can trigger additional inspection scrutiny. Best practice: fix the code and clear it before a planned inspection.
What's the difference between P0307 and related codes?
P0307 is closely related to: P0300 (Random/Multiple Cylinder Misfire Detected), P0301 (Cylinder 1 Misfire Detected), P0302 (Cylinder 2 Misfire Detected), P0303 (Cylinder 3 Misfire Detected). These codes share the same subsystem (ignition) and often appear together. If you see this code, scan for the full code list — fixing the root cause usually clears multiple companion codes at once. If only P0307 is set without the companions, the issue is more isolated.
How do I prevent P0307 from coming back after a repair?
For P0307 (Cylinder 7 Misfire Detected), prevention centers on the ignition system. Use OEM-spec injectors and spark plugs (gas). Address fuel quality issues immediately — bad fuel kills injectors. Cylinder balance test annually for early warning.