OBD2 Diagnostic Code
P0302
Cylinder 2 Misfire Detected — Symptoms, Causes & What to Do Next
P0302 locks the misfire onto one specific cylinder — and that is actually good news. You do not have to guess. Before your shop replaces injectors, coils, and plugs all at once, there is a five-minute test that narrows it down to one component and costs you absolutely nothing.
Severity
8 / 10
High. Active misfires send raw fuel into the catalytic converter and cause accelerated engine wear.
Safe to Drive?
No
Short trip to a shop only. A flashing check engine light means stop now — catalytic converter damage is happening in real time.
Typical DIY Fix Cost
Low – Moderate
A spark plug or coil swap fixes most cases. Only expensive if the issue is internal engine compression.
🔍 What This Code Means
Your engine fires each cylinder in a set sequence. Every time one cylinder fires, the crankshaft rotates a precise amount. P0302 means the computer detected a rotational irregularity that matches Cylinder 2 not completing its power stroke — the mixture was not burned, or was burned too weakly to move the piston properly.
The ECM counts misfire events over a rolling window of engine revolutions. When Cylinder 2 misfires frequently enough to trigger the threshold — typically around 2% of firing events within 1,000 RPM — the code is stored and the check engine light comes on. If the rate exceeds a second, higher threshold, the light will flash rather than stay on solid.
💡 A solid check engine light means the ECM has logged the fault but considers it manageable right now. A flashing check engine light means the misfire rate is high enough to damage the catalytic converter immediately. Treat a flashing light as a roadside emergency — pull over and do not continue driving.
The cylinder-specific nature of P0302 is an advantage. Unlike P0300 (random misfire), which can bounce between cylinders and is harder to diagnose, P0302 tells you exactly where to start. In most cases a single inexpensive part is the culprit, and the swap test below confirms which one in minutes.
⚡ Common Symptoms
On a 4-cylinder engine, a Cylinder 2 misfire removes 25% of the engine's working cylinders. You will feel it. On a 6- or 8-cylinder engine the effect is subtler but still present, especially at idle and low load.
Engine shudder at idle
The most immediate sign. The engine rocks and vibrates at a stop — you feel it in the steering wheel, the seat, and the center console. RPM may drop unpredictably below 700.
Jerking on light throttle
Pulling away from a stop or cruising at steady speed, the car surges and stumbles rhythmically. It often feels worse in lower gears and improves slightly at higher RPM.
Check engine light — solid or flashing
Solid means the code is stored. Flashing means severe ongoing misfire — catalytic converter damage is happening right now. Never continue driving with a flashing CEL.
Raw fuel smell at the tailpipe
Unburned gasoline from Cylinder 2 exits through the exhaust. The smell is strongest at idle. Left long enough, this fuel accumulates in and destroys the catalytic converter substrate.
Loss of power climbing hills
Under load, the missing cylinder's contribution becomes obvious. Acceleration feels soft and sluggish compared to normal, and the transmission may hunt for a lower gear to compensate.
Worse fuel economy
The ECM compensates for rough running by adjusting fueling. You may notice MPG dropping within a day or two — sometimes before you even feel the rough idle clearly.
🎯 Most Likely Causes
Listed most common to least. Work through these in order. The swap test — described in Step 2 below — confirms or clears ignition components without spending anything.
1
Worn or fouled spark plug — Cylinder 2
The plug is the first thing to check on any cylinder-specific misfire. Oil fouling, carbon buildup on the electrode tip, or a worn gap that has opened beyond spec all produce inconsistent ignition. Check the plug gap for your engine — most modern engines specify 0.028–0.060 inches. A plug that looks black and sooty or has a cracked insulator is well past due. Most Cylinder 2 misfires that started gradually over time are solved right here.
~ 38% of cases
2
Failing ignition coil (coil-on-plug) — Cylinder 2
On most modern engines each cylinder has a dedicated coil pack bolted directly onto the spark plug. A coil that is cracking internally or losing output produces a weak spark that cannot reliably ignite the mixture. Coil failures often worsen in wet or cold weather and may feel intermittent at first. The swap test is definitive: move the Cylinder 2 coil to Cylinder 3 and re-scan. If the misfire shifts to P0303, the coil is your answer.
~ 30% of cases
3
Clogged or leaking fuel injector — Cylinder 2
A partially clogged injector delivers less fuel than commanded, starving Cylinder 2 of the mixture it needs. A leaking injector floods it. Either fault produces a cylinder-specific misfire that does not follow the coil in a swap test. Listen for the rapid clicking of each injector at idle using a mechanic's stethoscope — silence from Cylinder 2 points directly at the injector circuit. Professional ultrasonic cleaning resolves partial clogs before replacement is warranted.
~ 15% of cases
4
Low compression on Cylinder 2
A burned exhaust valve, damaged piston rings, or a head gasket failure affecting Cylinder 2 starves the cylinder of the compression it needs to ignite the mixture — no ignition part in the world can fix that. If plug and coil replacements fail to clear P0302, perform a compression test. Healthy cylinders read 130–180 PSI. A reading more than 15% below the adjacent cylinders — or below 100 PSI outright — is a mechanical problem that needs professional assessment.
~ 10% of cases
5
Spark plug wire — Cylinder 2 (older distributor ignitions)
On vehicles with a distributor and individual plug wires rather than coil-on-plug, a cracked, arcing, or high-resistance wire on Cylinder 2 produces the same fault. Inspect the wire for burn marks and test resistance with a multimeter — more than 10,000 ohms per foot indicates a failing wire. Not applicable to most post-2000 vehicles with coil-on-plug systems.
~ 5% of cases
6
Wiring fault or corroded connector at Cylinder 2
A chafed injector wire, corroded coil connector pin, or damaged harness at Cylinder 2 mimics component failure without any component actually being bad. Inspect the wiring at both the coil and the injector before condemning parts. This is the root cause in roughly 2% of cases but is common on high-mileage vehicles that have had previous underhood repairs, particularly if wiring was disturbed and not re-secured correctly.
~ 2% of cases
🔧 What to Check First
These three steps resolve P0302 in the vast majority of cases and cost nothing to perform. Do them in order — cheapest and fastest first. The golden rule: swap before you buy.
1
Inspect and test the Cylinder 2 spark plug
Locate Cylinder 2 on your specific engine — on inline 4-cylinder engines it is typically the second plug from the timing end. Remove it and examine the tip carefully. A healthy plug is light tan or light grey. Black, sooty deposits indicate rich running or oil consumption. A white chalky tip suggests lean running or overheating. Measure the gap with a feeler gauge and compare to the specification in your owner's manual. Replace if fouled, worn, or out of spec. If other plugs on the same engine are past their service interval, replace all of them together — partial replacements create the same diagnostic visit again a few weeks later.
2
Perform the coil swap test
If a fresh plug does not resolve the misfire after clearing the code and driving 10–15 miles, move the Cylinder 2 coil pack to Cylinder 3 and put the Cylinder 3 coil on Cylinder 2. Clear the code and drive again. Check the result: if P0303 now appears instead of P0302, the coil you moved is faulty — replace it. If P0302 stays on Cylinder 2, the coil is innocent. This test is definitive, costs nothing, and takes under five minutes. Do not skip it and order a coil blind — the failure rate for guessing wrong is significant.
3
Check the Cylinder 2 injector for pulse
With the engine idling, press the tip of a long flathead screwdriver against the body of each injector and put your ear to the handle — you will hear a rapid, distinct ticking from a healthy injector. No tick from Cylinder 2 means it is not firing. Next, unplug the injector connector with the key on — test for battery voltage at the harness side. No voltage points to a wiring fault upstream of the injector. Voltage present with no injector pulse means the injector itself has failed electrically. Before replacing it, ask about professional ultrasonic cleaning — it resolves partial clogs at a fraction of replacement cost.
🚨 If the check engine light is flashing while you drive, do not continue. Pull over safely as soon as possible. A flashing CEL during active misfire means catalytic converter damage is occurring right now — every additional mile increases the repair bill significantly.
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⚠️ Common Misdiagnosis
These three misdiagnosis patterns drain money and time without fixing the underlying fault. Each one is avoidable if the right test is done first.
⚠ Misdiagnosis #1 — Replacing the coil without testing it first via swap
A coil failure and a spark plug failure produce nearly identical symptoms on a cylinder-specific misfire. The coil swap test — which costs nothing — separates them in one drive cycle. Shops that recommend a coil replacement based solely on a P0302 code, without first documenting a coil swap test result, are skipping the most important diagnostic step. Always ask: "Did you move the coil to another cylinder and confirm the misfire followed it?" If the answer is no, the diagnosis is incomplete.
Potential savings: Coil cost vs. a spark plug that costs far less
⚠ Misdiagnosis #2 — Replacing both the coil and the plug without doing either swap test
Replacing both components at once guarantees the car runs better — but tells you nothing. You have spent money on at least one part that was fine. Worse, if P0302 returns later, you still do not know which component actually caused the original fault. Good diagnostics means isolating one variable at a time: plug first, then coil. If both are legitimately past service life, replacing together is reasonable — but that decision should be based on mileage data, not guesswork.
Potential savings: Cost of whichever part was not actually faulty
⚠ Misdiagnosis #3 — Condemning the injector before confirming compression
When plug and coil replacements do not resolve P0302, fuel delivery gets blamed next. Before authorizing injector cleaning or replacement, a compression test on Cylinder 2 takes only a few minutes and can save a significant amount of money. A cylinder with low compression misfires regardless of how much fuel the injector delivers — cleaning or replacing the injector accomplishes nothing. Confirm compression is within range of the other cylinders before touching the fuel system.
Potential savings: Injector service cost when the real issue is mechanical
💰 Estimated Repair Cost
DIY cost = parts only. Shop cost = parts plus labor. Costs vary by vehicle, region, and shop rate. These are planning ranges — not quotes.
Spark plug replacement (single — Cylinder 2)
DIYVery Low
ShopLow
LevelVery Easy
Spark plug full set replacement
DIYLow
ShopLow–Moderate
LevelEasy
Ignition coil replacement (single)
DIYLow–Moderate
ShopModerate
LevelEasy
Fuel injector cleaning (Cylinder 2)
DIYLow
ShopModerate
LevelModerate
Fuel injector replacement (Cylinder 2)
DIYModerate
ShopModerate–High
LevelModerate
Catalytic converter replacement (if damaged by misfire)
DIYHigh
ShopVery High
LevelAdvanced
Valve or head gasket repair (low compression)
DIYHigh
ShopVery High
LevelProfessional
✅ The swap test keeps P0302 inexpensive in most cases. Plug and coil together cover roughly 68% of verified diagnoses. Compression problems are the exception, not the rule.
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🚗 Most Reported On
P0302 appears across all makes and models, but these vehicles generate above-average misfire reports on Cylinder 2 based on owner data and repair records.
Honda Civic (2006–2015, 1.8L R18 — carbon deposits)
Toyota Camry (2007–2014, 2.5L 2AR — coil failure)
Chevrolet Malibu (2008–2012, 2.4L Ecotec)
Ford Focus (2012–2018, 2.0L GDI — carbon buildup)
Nissan Altima (2007–2013, 2.5L QR25)
Jeep Wrangler (2012–2018, 3.6L Pentastar)
BMW 3 Series (2012–2019, N20/B48 — coil and plug)
Subaru Outback (2010–2014, 2.5L EJ25 — head gasket)
❓ Frequently Asked Questions
Is P0302 the same problem as P0301?
The fault type is identical — a cylinder-specific misfire — but the affected cylinder is different. P0301 is Cylinder 1, P0302 is Cylinder 2. This matters practically because ignition coils and injectors are cylinder-specific components. The coil on Cylinder 2 is a separate part from the one on Cylinder 1. Always confirm which cylinder is actually misfiring before replacing anything, and use the swap test to verify the faulty component before purchase.
Can P0302 damage my engine if I keep driving?
Yes — in two distinct ways. First, unburned fuel from Cylinder 2 enters the exhaust stream and ignites inside the catalytic converter. Repeated exposure overheats and destroys the converter substrate, which is significantly more expensive than whatever caused the misfire to begin with. Second, raw fuel washes the cylinder walls and strips away the oil film on the piston and rings, accelerating mechanical wear specifically on Cylinder 2. Neither effect is instant, but both compound with every mile you drive on an active misfire.
I replaced the coil on Cylinder 2 and P0302 came back. What now?
Start by confirming the replacement coil is functioning correctly — swap it to Cylinder 3 and check if P0303 appears. If the misfire stays on P0302 with a confirmed-good coil installed, move to the spark plug. If the plug was also replaced at the same time, move to the injector — listen for clicking at idle and verify voltage at the connector. If the injector appears functional, perform a compression test on Cylinder 2. Healthy compression reads 130–180 PSI. More than 15% below adjacent cylinders signals an internal mechanical fault.
Why does P0302 only appear when the engine is cold?
A misfire that appears only during cold starts and disappears once the engine warms up is a classic sign of a marginal ignition component — a coil or plug that is just barely functional. Cold conditions increase the electrical resistance in a weakened coil, reducing spark output below the threshold needed to ignite the mixture reliably. Once the coil warms up and resistance drops, it recovers enough to fire. Carbon deposits on a plug can also bridge the gap differently at cold temperatures. Replace the Cylinder 2 spark plug first. If the cold-start misfire persists, test the coil's primary winding resistance — a healthy coil reads 0.4–2 ohms.
How do I find Cylinder 2 on my specific engine?
On most inline 4-cylinder engines, cylinders are numbered sequentially from the timing end of the engine — so Cylinder 1 is closest to the timing belt or chain, and Cylinder 2 is the next one back toward the firewall. On V6 and V8 engines the numbering convention varies by manufacturer. Ford V8s number differently than GM V8s, and import brands follow their own patterns. Check your owner's manual or search your exact make, model, and engine size — getting the cylinder position wrong means pulling the wrong plug and not solving anything.
🔗 Related Codes
These codes share the same root causes as P0302 or commonly appear alongside it.
This guide is for informational purposes only. Always consult a qualified mechanic before performing any vehicle repair. OBDPlatform is not responsible for actions taken based on this content.