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High Severity — Powertrain OBD-II DTC

P0349: Camshaft Position Sensor A Circuit Intermittent (Bank 2)

P0349 is a generic powertrain DTC indicating: Camshaft Position Sensor A Circuit Intermittent (Bank 2).

⚡ Quick Summary

Severity
High
DIY Level
Moderate
Repair Cost
$40–$150
Urgency
Fix within days

What Does P0349 Mean?

Engine misfires are detected by monitoring crankshaft rotational speed variations. Each cylinder's power stroke produces a characteristic acceleration pattern. When a cylinder fails to fire, the crankshaft decelerates during that cylinder's stroke. The ECM identifies which cylinder misfired and how often. P0313-P0399 codes cover extended misfire monitoring including lean misfire detection, knock-related ignition faults, and secondary ignition monitoring. A flashing check engine light during active misfires is an emergency — raw unburned fuel enters the catalytic converter, potentially destroying it.

🚨 Symptoms of P0349

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

🔍 Common Causes of P0349

HIGH
Worn or fouled spark plugs
HIGH
Faulty ignition coil
MED
Vacuum leak causing lean misfire
MED
Fuel injector issue (clogged, leaking, or electrical)
MED
Low compression (worn rings, burned valve, head gasket)
LOW
Incorrect ignition timing

🛠️ How to Fix P0349

⭐ Most Common Fix

Replace spark plugs

💰 $40–$150 🔧 Easy

Replace ignition coil(s)

💰 $30–$150 🔧 Easy

Repair vacuum leak

💰 $50–$300 🔧 Moderate

Clean or replace fuel injector

💰 $50–$300 🔧 Moderate

Engine mechanical repair (valves, rings, gasket)

💰 $500–$3000 🔧 Hard

🔬 Step-by-Step Diagnosis

  1. 1 Check misfire counters in Mode 6 data — identifies which cylinder(s) are misfiring most
  2. 2 Swap ignition coil to another cylinder — if misfire follows, coil is bad
  3. 3 Check spark plugs — worn electrode, fouled with oil or carbon, cracked insulator all cause misfires
  4. 4 Perform compression test on affected cylinder(s) — low compression means mechanical issue
  5. 5 Check for vacuum leaks with a smoke machine — lean misfires are common

⚠️ Common Mistakes to Avoid

  • ✗ Replacing coils without checking spark plugs — a worn plug will kill a new coil
  • ✗ Ignoring a flashing check engine light — this means severe misfire that's damaging the catalytic converter NOW
  • ✗ Replacing ignition parts when the misfire is caused by a vacuum leak or low compression
  • ✗ Not checking fuel trims — positive fuel trim + misfire often means vacuum leak, not ignition

💡 Pro Tips

  • ★ If misfires are random across cylinders (P0300), suspect fuel pressure, MAF sensor, or vacuum leak rather than ignition components
  • ★ On GDI engines, carbon buildup on intake valves is a major misfire cause that doesn't respond to fuel additives — walnut blasting or chemical cleaning required
  • ★ Compression testing tip: a quick test is cranking amps — a cylinder with low compression draws less current during cranking, visible on a scope or amp clamp

❓ Frequently Asked Questions

What does a flashing check engine light mean? ▾
A flashing CEL means severe, active misfire that risks catalytic converter damage. Pull over safely and reduce engine load. Do not rev the engine. Drive gently to a repair facility or have it towed. This is the only CEL condition that warrants immediate action.
Can misfires damage my engine? ▾
Misfires themselves don't usually damage the engine, but they can destroy the catalytic converter ($1000-$3000). Severe misfires also dilute engine oil with raw fuel, reducing lubrication. Extended misfires should always be repaired promptly.
Why does my car misfire only when cold? ▾
Cold misfires are often caused by slightly worn spark plugs (gap too wide for cold, dense air-fuel mixture), marginal ignition coils that work fine once warm, or small vacuum leaks that are more noticeable at cold idle RPM.

🏥 When to See a Mechanic

Ignition coil and spark plug replacement is easy DIY. If misfires persist after ignition work, compression testing and vacuum leak diagnosis require more specialized tools. For GDI carbon cleaning or mechanical repairs, see a professional.

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Misfires O2 Sensors Catalytic Converter EVAP System VVT/Camshaft Fuel System Cooling System Throttle Knock Sensor EGR System

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.