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OBD Code P0308

Cylinder 8 Misfire Detected

CodeP0308
DescriptionCylinder 8 Misfire Detected
Possible CausesFaulty spark plug; Bad ignition coil; Leaking injector; Low compression
SymptomsRough idle; Misfire on cyl 8; Flashing CEL; Power loss
SystemIgnition

What Does P0308 Mean?

Cylinder 8 Misfire Detected. This diagnostic trouble code (DTC) is stored when the vehicle's onboard computer detects an issue with the ignition.

Code Breakdown

P = Powertrain code

0 = Generic (SAE standard)

How to Fix P0308

Follow these diagnostic steps to identify and resolve the issue. Always start with the simplest checks before moving to more involved repairs.

  1. Read freeze frame data to identify conditions when the misfire occurred (RPM, load, temperature).
  2. Inspect spark plugs for wear, fouling, or improper gap. Replace if necessary.
  3. Check ignition coils — swap the coil from the misfiring cylinder with a known good one to see if the misfire follows.
  4. Inspect fuel injectors for clogging or electrical issues. Test injector resistance with a multimeter.
  5. Check compression on the affected cylinder. Low compression indicates a mechanical issue (valves, head gasket, piston rings).
  6. Inspect vacuum lines and intake manifold gasket for leaks.
  7. Clear codes and test drive to verify the misfire is resolved.

Note: These are general diagnostic guidelines. Some vehicles may have model-specific procedures. Always consult your vehicle's service manual for exact specifications and torque values. If you are not comfortable performing these steps, visit a qualified mechanic.

Frequently Asked Questions

Is P0308 serious?

Yes, P0308 is considered a high-severity code. You should have it diagnosed and repaired as soon as possible. Driving with this code active may cause further damage to your vehicle or pose a safety risk.

Can I clear P0308 myself?

You can clear any OBD-II code with a code scanner or by disconnecting the battery for 15-30 minutes. However, clearing the code without fixing the underlying problem will cause it to return, usually within one or two drive cycles. If the code triggered the check engine light, the light will come back on. Fix the root cause first, then clear the code.

How much does it cost to fix P0308?

Repair costs vary widely depending on the root cause. Some fixes are free (like tightening a gas cap) while others can cost several hundred dollars (like replacing a catalytic converter or oxygen sensor). A proper diagnosis with a professional scan tool, not just reading the code, is the first step to getting an accurate repair estimate. Many auto parts stores offer free code reading, but a thorough diagnosis usually requires a mechanic.

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