Last updated: July 6, 2026. P0302 means Cylinder 2 Misfire Detected. The engine computer has detected misfire activity on cylinder number two. Common causes include a worn spark plug, weak ignition coil, cracked coil boot, bad plug wire, fuel injector issue, vacuum leak near cylinder 2, low compression, wiring fault, or mechanical engine problem.
P0302 can be serious when the misfire is active. If the check engine light flashes, the engine shakes, power drops, or raw fuel smell appears, stop driving when safe. Unburned fuel from a misfiring cylinder can overheat the catalytic converter. Save freeze frame before clearing codes.
P0302 Quick Facts
| Item | What it means |
|---|---|
| Code | P0302 |
| Definition | Cylinder 2 Misfire Detected |
| Main area | Ignition, fuel, air, compression, or mechanical issue on cylinder 2 |
| Common causes | Spark plug, coil, boot/wire, injector, vacuum leak, compression, wiring |
| Severity | High if check engine light flashes or engine shakes |
| Best scanner data | Freeze frame, misfire counters, fuel trims, RPM/load, pending codes |
P0302 is a cylinder-specific version of P0300. P0300 means random or multiple cylinder misfire. P0302 points to cylinder 2, so diagnosis can use targeted swap tests and cylinder comparison.
What P0302 Means
A misfire happens when a cylinder does not burn its air-fuel mixture correctly. The computer watches crankshaft speed changes and stores a cylinder code when one cylinder repeatedly contributes less power than expected. With P0302, cylinder 2 is the flagged cylinder.
Cylinder 2 location depends on engine layout. Do not assume cylinder order from left to right. Confirm the firing order and cylinder numbering for the exact engine before swapping coils, plugs, or injectors.
Common Symptoms
- Check engine light on.
- Flashing check engine light during acceleration.
- Rough idle or engine shake.
- Hesitation under load.
- Loss of power.
- Fuel smell from exhaust.
- Poor fuel economy.
- Hard start or cold-start stumble.
If P0302 appears with lean codes such as P0171 or P0174, check fuel trims and intake leaks before replacing multiple ignition parts. A lean condition can show up as one cylinder misfire first.
Common Causes of P0302
| Cause | Why it creates P0302 | First check |
|---|---|---|
| Worn spark plug | Weak spark on cylinder 2 | Plug age, gap, fouling, cracks |
| Weak ignition coil | Spark fails under load or heat | Coil swap test if accessible |
| Bad boot or plug wire | Spark leaks before reaching plug | Carbon tracking, oil, burn marks, cracks |
| Fuel injector problem | Cylinder 2 gets too little or too much fuel | Connector, injector pulse, balance test |
| Vacuum leak near cylinder 2 | One cylinder runs lean | Intake gasket, hose, smoke test |
| Low compression | Cylinder cannot make normal power | Compression or leak-down test |
| Mechanical issue | Valve, ring, cam, head gasket, or timing issue | Compression, leak-down, borescope clues |
How to Diagnose P0302
Use cylinder-specific testing. Good diagnosis shows whether the misfire follows a moved part, stays on cylinder 2, or changes with fuel trim, load, or temperature.
- Scan all codes. Record P0302 plus any P0300, fuel trim, oxygen sensor, MAF, injector, cam/crank, or catalyst codes.
- Save freeze frame. Note RPM, load, speed, coolant temperature, fuel trims, and whether the code set at idle or under load.
- Confirm cylinder 2 location. Use correct cylinder numbering for exact engine.
- Inspect spark plug and boot. Look for worn electrode, wide gap, oil, coolant staining, cracks, or carbon tracking.
- Swap ignition coil if safe. Move cylinder 2 coil to another cylinder. If misfire follows, coil is suspect.
- Swap or inspect spark plug. If plug damage follows, plug is suspect. Use correct type and gap.
- Check fuel trims. High positive trims suggest lean mixture, vacuum leak, MAF issue, or fuel delivery problem.
- Check injector and wiring. Inspect connector, harness, injector pulse, and injector operation before replacement.
- Perform compression test if fault stays on cylinder 2. Mechanical fault becomes more likely when spark and fuel checks pass.
- Clear codes after repair and road test. Confirm P0302 and pending misfire do not return.
If scanner supports misfire counters, compare cylinder 2 with nearby cylinders. A scanner with live data helps show whether misfire occurs at idle, under load, cold, or hot. Compare scanner options in our OBD2 scanner with live data guide.
Scanner Data to Check
| Data point | Why it matters |
|---|---|
| Freeze frame | Shows conditions when P0302 set |
| Misfire counters | Shows cylinder 2 pattern if supported |
| RPM and load | Separates idle misfire from load misfire |
| STFT and LTFT | Shows lean/rich correction clues |
| Coolant temperature | Shows cold or hot misfire pattern |
| MAF data | Helps with airflow and lean clues |
| Pending codes | Shows early return before light comes back |
Phone-based scanners can help if they save freeze frame and graph trims. If you prefer app diagnostics, compare the best Bluetooth OBD2 scanner options.
P0302 vs P0301
| Code | Misfire location | Best first action |
|---|---|---|
| P0301 | Cylinder 1 | Confirm cylinder 1, inspect/swap coil and plug |
| P0302 | Cylinder 2 | Confirm cylinder 2, inspect/swap coil and plug |
| P0300 | Random/multiple cylinders | Look for shared ignition, fuel, air, or mechanical cause |
Common Mistakes
- Replacing all coils before testing cylinder 2.
- Not confirming cylinder numbering.
- Clearing code before saving freeze frame.
- Ignoring fuel trims and vacuum leaks.
- Replacing injector before checking spark plug, coil, and wiring.
- Skipping compression test when misfire stays on cylinder 2.
- Driving with flashing check engine light.
Can I Drive With P0302?
Do not keep driving if check engine light flashes, engine shakes badly, power drops, or raw fuel smell appears. Active misfire can damage catalytic converter quickly.
If light is steady and engine runs mostly normal, short gentle driving may be possible, but diagnosis should happen soon. If catalyst code appears later, read the P0420 code guide before replacing converter parts.
Related Codes
P0302 can appear with P0300, P0301, P0303-P0308, P0171, P0174, P0101, injector circuit codes, cam/crank sensor codes, or catalyst codes. If airflow data looks wrong, use the P0101 code guide. If scanner shows multiple code types, read stored vs pending vs permanent codes before clearing anything.
Final Advice
For P0302, confirm cylinder 2 location, save freeze frame, inspect plug and coil, use swap testing where possible, check fuel trims, then test injector and compression if misfire stays on cylinder 2. Replace parts only when test results point there.
If you need a scanner for freeze frame, pending codes, fuel trims, and misfire clues, start with the main best OBD2 scanner guide.
FAQ
What is most common cause of P0302?
Common causes include worn spark plug, weak ignition coil, damaged boot or plug wire, injector issue, vacuum leak near cylinder 2, or low compression.
Can I swap coils to diagnose P0302?
Yes, when coils are accessible and same type. Move cylinder 2 coil to another cylinder. If misfire follows coil, coil is likely fault.
Can bad injector cause P0302?
Yes. Clogged, leaking, or electrically faulty injector can cause cylinder 2 misfire. Check ignition and wiring before injector replacement.
Is P0302 safe to drive?
Not if check engine light flashes or engine shakes badly. Stop driving when safe because active misfire can damage catalytic converter.
Written by Michael Hayes
Written by Michael Hayes, editor of Best OBD2 Scanner. Michael researches OBD2 scanners, diagnostic apps, trouble codes, live data features, and vehicle compatibility so readers can choose tools with fewer surprises.
