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High Severity — Powertrain OBD-II DTC

P0308: Cylinder 8 Misfire Detected

P0308 is a generic (SAE standard) powertrain diagnostic trouble code (DTC) indicating: Cylinder 8 Misfire Detected. This code is set when the vehicle's onboard computer (ECM/PCM) detects a fault in the ignition system or misfire system.

⚡ Quick Summary

Severity
High
DIY Level
Moderate
Repair Cost
$80–$300
Urgency
Fix within days

🚨 Symptoms of P0308

▸ Check engine light on (may flash during active misfire)
▸ Engine misfiring — rough idle, stumbling, or shaking
▸ Loss of power during acceleration
▸ Increased emissions and fuel consumption
▸ Possible catalytic converter damage if ignored

🔍 Common Causes of P0308

HIGH
Faulty ignition system or misfire component
MED
Wiring issue — open, short, or corroded connector
LOW
ECM/PCM software issue or internal failure

🛠️ How to Fix P0308

⭐ Most Common Fix

Diagnose and repair ignition system or misfire circuit

💰 $80–$300 🔧 Moderate

Repair or replace damaged wiring/connectors

💰 $50–$200 🔧 Easy

Replace faulty ignition system or misfire component

💰 $150–$500 🔧 Moderate

🔬 Step-by-Step Diagnosis

  1. 1 Check for misfire counters in Mode 6 data — identifies which cylinder is misfiring
  2. 2 Inspect spark plugs for wear, fouling, or damage
  3. 3 Test ignition coils — swap suspect coil to another cylinder and see if misfire follows
  4. 4 Check compression on affected cylinder(s) to rule out mechanical issues
  5. 5 Inspect fuel injectors if ignition components test good

⚠️ Common Mistakes to Avoid

  • ✗ Replacing only the spark plug without checking the ignition coil
  • ✗ Ignoring a flashing check engine light — this indicates severe misfire and potential catalytic converter damage
  • ✗ Not checking for vacuum leaks that can cause lean misfires
  • ✗ Replacing ignition parts on all cylinders when only one is affected

💡 Pro Tips

  • ★ Always check for Technical Service Bulletins (TSBs) for your specific vehicle — manufacturers often release updated repair procedures for common P0308 issues.
  • ★ Before replacing expensive parts, verify power, ground, and signal at the component connector with a multimeter.

❓ Frequently Asked Questions

What does P0308 mean? ▾
P0308 means Cylinder 8 Misfire Detected. The vehicle's computer has detected a fault in this system that needs diagnosis.
Can I drive with code P0308? ▾
This is a serious issue. You can drive short distances but should have it diagnosed soon to prevent further damage.
How much does it cost to fix P0308? ▾
Repair costs vary widely depending on the root cause. Diagnosis typically costs $80-$150. Repairs can range from $50 for simple fixes to $500+ for major component replacements. Always get a diagnosis before authorizing repairs.

🏥 When to See a Mechanic

If you're not comfortable with electrical diagnosis or don't have a multimeter and OBD-II scanner, have a qualified mechanic diagnose P0308. This code involves the ignition system or misfire system which may require specialized knowledge.

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Disclaimer: This information is for educational purposes only. It is not intended as repair advice and we are not responsible for any actions you take on any vehicle. Always consult a qualified mechanic for diagnosis and repair. Repair costs shown are estimates and may vary by location, vehicle, and shop.