What does P0302 mean?
The engine control module detected repeated misfires specifically in cylinder 2.
Quick Decision Guide
- Worn or fouled spark plug in cylinder 2
- Failing ignition coil on cylinder 2
- Clogged or leaking fuel injector on cylinder 2
When to stop driving
A flashing check-engine light on P0302 means cylinder 2 is actively misfiring and raw fuel is reaching the catalytic converter — reduce driving and inspect promptly. Stop driving if you also feel severe shaking, smell fuel, notice overheating, or lose power. A steady light with only mild roughness usually allows cautious short-distance driving to a safe location for inspection, but P0302 should still be diagnosed within days.
Reviewed by ratchit Automotive Solutions for clarity and inspection-first safety framing. Not a substitute for professional diagnosis.
Repair Decision & Cost Guide
Use this guide to decide what to inspect first, what it may cost, and when to move from DIY checks to professional diagnosis.
P0302 points to a misfire condition, not a guaranteed failed coil or plug. Isolate the failing cylinder before buying parts.
DIY vs. Shop
Can you keep driving?
Best first DIY check
Don't replace this first
When to seek a shop
Recommended next action
Estimated Repair Cost
Inspection cost
$0–$25 DIY scanner
DIY parts cost
$5–$120
Inspect first before replacing parts.
If the vehicle is unsafe to drive, stop driving and seek professional help.
Shop diagnostic cost
$80–$150 (typical shop diagnostic fee)
Shop repair cost
$40–$500
Diagnostic uncertainty: This code points to a system or condition, not a guaranteed failed part. Inspect before replacing.
Cost variation: Costs vary by vehicle, location, part quality, labor rate, and the confirmed root cause.
Inspect Before Replacing
These checks are cheap, fast, and rule out the most common causes before spending money on parts.
- 1Scan for companion codes (lean codes, MAF, cam/crank correlation) — they change what is worth inspecting on cylinder 2 first.
- 2Confirm the misfire is still isolated to cylinder 2 with a live-data misfire counter before touching parts.
- 3Pull the cylinder 2 spark plug and read it — fouling, oil, cracked insulator, or heavy wear each point to different root causes.
Track this misfire issue
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ratchit AI Insight
· P0302What this usually means:P0302 narrows the misfire to a specific cylinder, but the cause still needs to be confirmed before replacing parts. Misfire codes do not automatically mean spark plugs or coils are bad — air/fuel, vacuum, fuel delivery, and mechanical issues can all trigger the same code.
Common mistake: Many drivers replace all the spark plugs and coils first. That sometimes fixes it, but if the real cause is a vacuum leak, an injector problem, or low compression, the misfire returns and the parts money is wasted.
Inspect before replacing parts
- 1Check for a flashing check-engine light — a flashing CEL during a misfire is a high-risk condition for the catalytic converter.
- 2Swap the suspect coil/plug to a known-good cylinder and re-scan to see if the misfire follows.
- 3Inspect for obvious vacuum leaks, cracked intake boots, and disconnected PCV hoses.
- 4Review fuel trims and injector behavior before assuming an ignition part is bad.
Confirming the cylinder and the system (ignition vs. air/fuel vs. mechanical) before buying parts usually keeps the repair in the $20–$200 range instead of replacing a full ignition set.
Safety threshold: If the check-engine light is flashing, stop driving as soon as it is safe — continued driving in this state can damage the catalytic converter.
AI-assisted guidance reviewed against ratchit's inspection-first safety rules. Codes are clues, not confirmed diagnoses — always verify before replacing parts.
Understanding P0302 in detail
P0302 means the ECM has counted enough missed power strokes on cylinder 2 to flag it individually, rather than the random-cylinder pattern that would set P0300. Because the fault is isolated to one cylinder, the diagnostic path is narrower than a random misfire: the cause lives in whatever supplies spark, fuel, compression, or air to cylinder 2 specifically. That can be a worn or fouled spark plug, a weakening ignition coil, a partially clogged or leaking injector, a cracked intake boot or vacuum leak feeding that runner, damaged wiring or a corroded connector at the coil or injector, or low compression from a burnt valve, worn ring, or head gasket seepage. A coil or plug is a common outcome, but not a guaranteed one — swapping parts before confirming the fault often just moves the misfire to another cylinder or leaves it in place. The goal on P0302 is to prove which subsystem is failing on cylinder 2 before spending money, because unresolved misfires dump raw fuel into the exhaust and can damage the catalytic converter.
Symptoms of P0302
- Check engine light on or flashing
- Rough idle with noticeable vibration
- Loss of power during acceleration
- Engine stumbling or hesitation
- Fuel smell from exhaust
Common causes
- Worn or fouled spark plug in cylinder 2
- Failing ignition coil on cylinder 2
- Clogged or leaking fuel injector on cylinder 2
- Vacuum leak near cylinder 2 intake runner
- Damaged wiring or connector at the cylinder 2 coil or injector
- Low compression in cylinder 2 (valve, ring, or head-gasket issue)
How to diagnose P0302
Steps ordered by urgency — tackle Now items first.
- NowScan for companion codes (lean codes, MAF, cam/crank correlation) — they change what is worth inspecting on cylinder 2 first.
- NowConfirm the misfire is still isolated to cylinder 2 with a live-data misfire counter before touching parts.
- NowPull the cylinder 2 spark plug and read it — fouling, oil, cracked insulator, or heavy wear each point to different root causes.
- SoonIf the plug looks acceptable, swap the cylinder 2 coil with a neighboring cylinder, clear the code, and see whether the misfire follows the coil.
- SoonIf ignition checks pass, verify injector signal at cylinder 2 (noid light or scope) and inspect wiring/connectors before condemning the injector.
- LaterIf ignition and fuel both check out, perform a compression or leakdown test on cylinder 2 to rule out valves, rings, or head gasket.
- LaterSmoke-test the intake for a vacuum leak near the cylinder 2 runner if fuel trims run lean.
How to fix P0302
Fixes listed in order of likelihood and cost-efficiency.
- 1Replace the cylinder 2 spark plug when inspection shows wear, fouling, or damage
- 2Replace the cylinder 2 coil only after a swap test confirms the misfire follows it
- 3Clean or replace the cylinder 2 injector when signal and flow tests fail
- 4Repair wiring or connector damage at the cylinder 2 coil or injector
- 5Repair the intake or vacuum leak feeding cylinder 2
- 6Address low compression (valves, rings, or head gasket) if mechanical tests fail
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Recommended tools & parts
These recommendations appear because this issue commonly requires inspection in this system area. ratchit does not recommend replacing parts until the likely cause is confirmed.
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Estimated Repair Cost — P0302
Ranges vary by vehicle, region, and shop. Use as a ballpark — always get a quote.
DIY estimate
$5 – $15
Shop estimate
$40 – $100
DIY estimate
$25 – $70
Shop estimate
$100 – $300
DIY estimate
$40 – $120
Shop estimate
$200 – $500
Cost data is estimated and may not reflect your specific vehicle or location.
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Frequently Asked Questions
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