What causes fault code P0308?

• Most likely: Defective ignition coil (COP - Coil on Plug) • Likely: Worn or fouled spark plugs • Possible: Faulty fuel injector (electrical failure or clogging) • Possible: Intake manifold vacuum leak near cylinder 8 • Rare: Engine mechanical issue (low compression, burnt valve, or worn cam lobe) • Rare: Wiring harness issues in the ignition or injection circuit

How do you fix fault code P0308?

STEP 1: Perform a 'Swap Test'. Move the ignition coil from cylinder 8 to another cylinder (e.g., cyl 1). Check if the fault code follows the coil (P0301). If it does, replace the ignition coil. STEP 2: Inspect the spark plug on cylinder 8 for electrode wear or fouling. Resistance should generally be between 3-10 kOhms. STEP 3: Check wiring and connectors. Measure supply voltage (12V) at the coil and verify ground. Use an oscilloscope to verify the ECU trigger signal (Duty-cycle). STEP 4: If the fault persists, perform a compression or leak-down test on cylinder 8 to rule out internal mechanical damage. Also, test fuel injector resistance (typically 12-16 Ohms).

Powertrain (Engine & Gearbox)Standard EOBD

P0308 - Cylinder 8 Misfire Detected

Q: What are the symptoms of fault code P0308?

• Check engine light (MIL) illuminated or flashing • Engine hesitation, stumbling, or vibrations • Loss of power during acceleration • Raw fuel smell from the exhaust • Reduced fuel economy • Hard starting conditions

Last updated:1 February 2026

Related:Tennspole, Tennplugg, Drivstoffdyse, Crankshaft Position Sensor, ECU / Motorstyreenhet

System

Powertrain (Engine & Gearbox)

Related Fault Codes

P0300

Random or Multiple Cylinder Misfire Detected

P0301

Cylinder 1 Misfire Detected

P0302

Cylinder 2 Misfire Detected

P0303

Cylinder 3 Misfire Detected

Technical Description

P0308 indicates that the Engine Control Unit (ECU) has detected a misfire occurring on cylinder number 8. The ECU monitors the Crankshaft Position (CKP) sensor to detect minute fluctuations in crankshaft rotational speed during the power stroke of each cylinder. If cylinder 8 fails to contribute sufficient torque, a misfire is recorded. If the misfire rate is high enough to potentially damage the catalytic converter (due to unburned fuel entering the exhaust), the Malfunction Indicator Lamp (MIL) will flash.

Possible Causes

Defective ignition coil (COP - Coil on Plug)

Worn or fouled spark plugs

Faulty fuel injector (electrical failure or clogging)

Intake manifold vacuum leak near cylinder 8

Engine mechanical issue (low compression, burnt valve, or worn cam lobe)

Wiring harness issues in the ignition or injection circuit

Symptoms

Check engine light (MIL) illuminated or flashing

Engine hesitation, stumbling, or vibrations

Loss of power during acceleration

Raw fuel smell from the exhaust

Reduced fuel economy

Hard starting conditions

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P0308 - Cylinder 8 Misfire Detected

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P0308 - Cylinder 8 Misfire Detected

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