The P0302 OBD-II trouble code means the engine control module has detected a misfire specifically associated with Cylinder 2.

Unlike P0300, which indicates random or multiple-cylinder misfires, P0302 narrows the problem to one cylinder. That makes diagnosis easier, but it does not automatically mean the Cylinder 2 ignition coil has failed.

Cylinder 2 still needs air, fuel, spark, compression, and correct valve timing. A failure in any of those areas can trigger P0302.

P0302 Quick Answer

Item	Information
Trouble code	P0302
Definition	Cylinder 2 Misfire Detected
System	Ignition and combustion
Severity	High
Safe to drive?	Only briefly if the misfire is mild and the Check Engine Light is not flashing
Most common causes	Spark plug, ignition coil, fuel injector, wiring, vacuum leak, or low compression
Common symptoms	Rough idle, shaking, hesitation, power loss, and flashing Check Engine Light
Typical repair range	Approximately $30 to $5,000+, depending on the cause

P0302 belongs to the P0300-series misfire family covered in the complete Pro Street P-code OBD-II guide.

What Does the P0302 Code Mean?

P0302 stands for:

P: Powertrain
0: Generic OBD-II code
3: Ignition or misfire-related fault
02: Cylinder 2

The powertrain control module monitors small changes in crankshaft speed during each combustion event. When Cylinder 2 contributes less power than expected, the crankshaft briefly slows. If that pattern occurs often enough, the computer stores P0302.

The code identifies the affected cylinder. It does not identify the failed component.

That distinction matters because throwing an ignition coil at every misfire is diagnosis by credit card. Occasionally it works. It is still not diagnosis.

For a broader explanation of how misfires develop, see our engine misfire symptoms, causes, and diagnosis guide.

Where Is Cylinder 2 Located?

Cylinder 2 location depends on the engine design and manufacturer.

On an inline engine, the cylinders are normally arranged in one row, but numbering direction can vary. On V6, V8, and other multi-bank engines, Cylinder 2 may be located on either bank depending on the manufacturer’s numbering convention.

Do not assume Cylinder 2 is the second spark plug you can see.

Before disconnecting an ignition coil or injector, verify the firing order and cylinder-numbering diagram using:

Factory service information
A manufacturer repair manual
An underhood emissions label
A trusted vehicle-specific wiring or firing-order diagram

Testing the wrong cylinder can create a second problem while leaving the original one sitting there, quietly judging you.

Common P0302 Symptoms

A Cylinder 2 misfire may be constant, intermittent, or only present under certain operating conditions.

Common symptoms include:

Check Engine Light
Flashing Check Engine Light
Rough or unstable idle
Engine shaking
Hesitation during acceleration
Reduced engine power
Hard starting
Stalling
Poor fuel economy
Raw fuel smell from the exhaust
Increased exhaust emissions
Engine vibration under load
Reduced turbo boost or limp mode
Additional fuel-trim or ignition codes

A light-load misfire may only appear at idle. A weak ignition coil may misfire primarily under boost or heavy acceleration because higher cylinder pressure requires more ignition voltage.

The freeze-frame data stored with P0302 can help determine when the failure occurred.

How Serious Is P0302?

P0302 should be treated as a high-priority trouble code.

An active misfire can allow unburned fuel to enter the exhaust. That fuel may ignite inside the catalytic converter, causing the converter to overheat and fail.

Continued driving can also contribute to:

Catalytic converter damage
Oxygen sensor contamination
Cylinder-wall fuel wash
Engine oil dilution
Burned exhaust valves
Damaged pistons
Excessive vibration
Damage to engine or transmission mounts

Stop Driving Immediately If:

The Check Engine Light is flashing
The engine is shaking violently
Power loss is severe
The vehicle is stalling
A strong raw-fuel smell is present
The engine is overheating
Mechanical knocking or abnormal valvetrain noise is heard

A flashing Check Engine Light usually indicates a catalyst-damaging misfire. Reduce engine load, pull over safely, and shut the engine off.

If the light is steady and the engine runs reasonably well, driving a short distance for diagnosis may be possible. Avoid high RPM, heavy throttle, towing, and boost.

Most Common Causes of P0302

P0302 can be caused by ignition, fuel, air, compression, timing, or electrical problems.

Possible cause	Relative likelihood
Worn or fouled spark plug	Very high
Weak or failed ignition coil	Very high
Damaged coil boot or plug wire	High
Faulty or clogged fuel injector	High
Injector or coil wiring fault	Medium
Intake manifold gasket leak near Cylinder 2	Medium
Low compression	Medium
Burned or leaking valve	Medium
Carbon buildup on an intake valve	Medium on direct-injected engines
Damaged piston ring	Lower
Valve timing or valvetrain problem	Lower
Head gasket failure	Lower
PCM driver failure	Rare

The most common cause depends heavily on the vehicle, engine, mileage, maintenance history, and conditions recorded in the freeze-frame data.

Tools Needed to Diagnose P0302

Useful diagnostic tools include:

OBD-II scanner
Scan tool with live misfire data
Digital multimeter
Spark tester
Spark plug socket
Compression tester
Cylinder leak-down tester
Noid light
Fuel injector probe or mechanic’s stethoscope
Smoke machine
Fuel-pressure gauge where applicable
Vehicle-specific wiring diagram
Factory service information

A basic scanner can retrieve P0302. A better scan tool may display individual-cylinder misfire counters, fuel trims, injector commands, Mode $06 data, and freeze-frame information.

How to Diagnose P0302

Step 1: Confirm the Code

Connect an OBD-II scanner and record all stored, pending, and permanent codes.

Do not clear anything yet.

Record the P0302 freeze-frame information, including:

Engine RPM
Engine load
Vehicle speed
Coolant temperature
Intake-air temperature
Short-term fuel trim
Long-term fuel trim
Fuel-system status
Throttle position

The operating conditions provide useful clues.

For example:

When P0302 occurs	Possible direction
Cold start	Injector leak, carbon buildup, coolant intrusion, weak compression
Warm idle	Vacuum leak, injector imbalance, compression problem
Heavy acceleration	Weak coil, worn plug, insufficient fuel delivery
Wet weather	Coil boot, plug wire, or connector insulation
After refueling	Fuel quality or EVAP-related issue
Constantly	Dead coil, injector failure, wiring fault, or mechanical damage

Step 2: Check for Related Trouble Codes

P0302 may appear with other diagnostic codes.

Common companions include:

P0300 — Random/Multiple Cylinder Misfire
P0301 — Cylinder 1 Misfire
P0303 — Cylinder 3 Misfire
P0304 — Cylinder 4 Misfire
P0171 or P0174 — Lean condition
P0172 or P0175 — Rich condition
P0202 — Cylinder 2 Injector Circuit
P0352 — Ignition Coil B Circuit
Camshaft or crankshaft position codes

Multiple misfire codes may indicate a system-wide problem rather than a failure isolated to Cylinder 2.

Examples include:

Low fuel pressure
Contaminated fuel
Large vacuum leak
Incorrect valve timing
Failed mass airflow sensor
Crankshaft position signal problem
Charging-system voltage problem

Step 3: Verify Cylinder 2

Locate Cylinder 2 using reliable vehicle-specific information.

Then inspect the area for:

Disconnected electrical connectors
Oil or coolant inside the spark plug well
Damaged coil wiring
Rodent damage
Loose grounds
Cracked vacuum hoses
Intake manifold leaks
Burned or melted insulation

Oil inside a spark plug tube can damage the coil boot and allow ignition voltage to escape before it reaches the spark plug.

Step 4: Inspect the Cylinder 2 Spark Plug

Remove the Cylinder 2 spark plug and inspect it carefully.

Look for:

Worn electrodes
Excessive gap
Cracked porcelain
Carbon fouling
Wet fuel deposits
Oil contamination
Coolant deposits
Overheating
Incorrect plug type
Improper torque

Compare it with a plug from a healthy cylinder.

A wet fuel-covered plug may indicate that the injector is delivering fuel but the cylinder has no spark. A dry plug may suggest insufficient fuel delivery. Heavy oil deposits can point toward valve-seal, piston-ring, or PCV-related problems.

If the spark plugs are worn beyond the manufacturer’s service interval, replace the full set with the correct type and gap.

Step 5: Swap the Ignition Coil

If the engine uses coil-on-plug ignition, swap the Cylinder 2 coil with a known-good cylinder.

For example, move the Cylinder 2 coil to Cylinder 3. Clear the codes and operate the vehicle under similar conditions.

If the code changes from:

P0302 to P0303

the ignition coil is likely defective.

If P0302 returns on Cylinder 2, the coil probably is not the cause.

Inspect the coil boot and internal spring for:

Carbon tracking
Cracks
Moisture
Corrosion
Oil contamination
Burned terminals

Our ignition coil replacement guide explains how to replace coils without guessing or accidentally creating a fresh collection of misfire codes.

Engines using a distributor, coil pack, or spark plug wires require a different ignition test. Inspect plug-wire resistance, routing, insulation, and coil-pack output according to factory specifications.

Step 6: Test the Cylinder 2 Fuel Injector

A clogged, leaking, electrically open, or mechanically stuck injector can cause P0302.

Begin by listening for a consistent clicking sound from the injector. Compare Cylinder 2 with the other injectors.

Further testing may include:

Injector resistance test
Injector voltage test
Noid-light test
Current-ramp test
Injector balance test
Fuel-pressure drop test
Injector swap test where practical

Resistance specifications vary by injector design and vehicle. Compare the measurement with factory specifications rather than trusting a universal number from the internet, humanity’s most confident source of occasionally wrong information.

Useful vehicle-specific references include:

Never loosen a fuel line on a gasoline direct-injection or diesel common-rail system without following the manufacturer’s pressure-relief procedure. These systems operate at pressures capable of causing serious injury.

Step 7: Inspect the Coil and Injector Circuits

If the ignition coil and injector test correctly, inspect their circuits.

Check for:

Correct supply voltage
Reliable ground
Injector control pulse
Ignition-coil trigger signal
Loose connector terminals
Corroded pins
High circuit resistance
Wiring shorted to voltage or ground
Harness damage near hot or moving components

Perform voltage-drop testing whenever possible. A circuit may pass a basic continuity test while failing under load.

PCM failure is possible, but it should be considered only after the component, wiring, power supply, grounds, and mechanical condition have been verified.

Step 8: Check for a Vacuum or Intake Leak

An intake leak located near the Cylinder 2 runner can create a cylinder-specific lean misfire.

Inspect:

Intake manifold gasket
Injector seal
Vacuum hoses
PCV connections
Brake-booster hose
Intake manifold cracks
Throttle-body gasket

A smoke test is generally the safest and most effective way to locate an intake leak.

Fuel-trim data can provide another clue. Strongly positive fuel trim at idle that improves as engine speed increases often points toward a vacuum leak.

Step 9: Perform a Compression Test

If spark, fuel, and electrical tests do not explain P0302, test engine compression.

Compare Cylinder 2 with the remaining cylinders. The exact acceptable pressure and variation must come from the vehicle manufacturer.

Low Cylinder 2 compression may be caused by:

Burned intake or exhaust valve
Bent valve
Worn piston rings
Damaged piston
Broken valve spring
Collapsed lifter
Worn camshaft lobe
Head gasket leak
Cylinder-wall damage
Incorrect valve timing

A wet compression test can help separate ring-related leakage from valve-related leakage, but a cylinder leak-down test provides more useful information.

Step 10: Perform a Leak-Down Test

Introduce regulated compressed air into Cylinder 2 at top dead center on the compression stroke.

Listen for escaping air:

Air heard or observed at	Likely problem
Throttle body or intake	Intake valve leakage
Exhaust outlet	Exhaust valve leakage
Oil filler opening	Piston rings or cylinder damage
Cooling system	Head gasket, cylinder head, or block damage
Adjacent cylinder	Head gasket failure between cylinders

This test can prevent an impressive amount of unnecessary parts replacement.

Step 11: Check for Carbon Buildup

Gasoline direct-injection engines can develop intake-valve deposits because fuel no longer washes over the back of each intake valve.

Uneven carbon buildup near Cylinder 2 may cause:

Cold-start misfires
Rough idle
Airflow imbalance
P0302 that improves as the engine warms

A borescope inspection can help confirm deposit buildup. Approved cleaning procedures vary by manufacturer and may include media blasting or specialized chemical cleaning.

Do not assume that pouring an additive into the fuel tank will clean a direct-injected intake valve. The fuel never touches it. Physics remains stubbornly unimpressed by the label on the bottle.

Step 12: Clear the Code and Confirm the Repair

After completing the repair:

Clear stored and pending codes.
Start the engine and verify a stable idle.
Monitor Cylinder 2 misfire counters.
Recreate the original freeze-frame conditions when safe.
Complete the required drive cycle.
Rescan for pending codes.
Confirm that readiness monitors complete normally.

A repair is not confirmed simply because the Check Engine Light stays off for five minutes.

Common P0302 Repairs and Costs

Actual prices depend on the vehicle, labor rate, parts quality, and accessibility.

Repair	Approximate installed cost
Replace spark plugs	$50–$400
Replace one ignition coil	$80–$450
Repair coil boot or plug wire	$30–$250
Clean or replace one injector	$150–$900
Repair wiring or connector	$100–$600
Repair intake or vacuum leak	$100–$800
Intake valve carbon cleaning	$400–$1,500
Replace intake manifold gasket	$300–$1,200
Cylinder-head or valve repair	$1,500–$5,000+
Engine replacement	$4,000–$12,000+

Diagnosis should come before the estimate. A $30 damaged connector and a $5,000 mechanical failure can store the same P0302 code.

Common P0302 Diagnostic Mistakes

Replacing the Ignition Coil Without Testing

Coils fail frequently, but P0302 does not prove that Coil 2 is defective. Swap-testing the coil is faster and more reliable than guessing.

Ignoring the Spark Plug

A new coil installed over a cracked, oil-fouled, or incorrectly gapped plug will not solve the problem for long.

Replacing All Injectors

Test injector operation before replacement. One cylinder-specific code does not automatically justify replacing the entire set.

Clearing Freeze-Frame Data Too Early

Freeze-frame data may be the only record of the conditions that triggered the misfire.

Skipping Compression Testing

If the ignition and fuel systems test correctly, stop buying parts and test the engine mechanically.

Using the Wrong Cylinder Layout

Always verify the manufacturer’s cylinder numbering. Cylinder 2 is not necessarily where intuition, tradition, or the guy in the comment section says it is.

Replacing the Catalytic Converter First

A damaged converter may be the result of a long-term misfire, not the original cause. Repair the misfire before condemning the converter.

P0302 Frequently Asked Questions

Does P0302 Mean the Ignition Coil Is Bad?

No. A failed ignition coil is common, but a spark plug, injector, wiring problem, intake leak, compression loss, or mechanical fault can also cause P0302.

Can a Bad Spark Plug Cause P0302?

Yes. A worn, fouled, cracked, or incorrectly gapped Cylinder 2 spark plug is one of the most common causes.

Can a Fuel Injector Cause P0302?

Yes. A clogged, leaking, electrically failed, or unpowered Cylinder 2 injector can create a cylinder-specific misfire.

Can a Vacuum Leak Cause Only One Cylinder to Misfire?

Yes. An intake manifold gasket leak or injector-seal leak near the Cylinder 2 runner can affect that cylinder more than the others.

Can Low Compression Trigger P0302?

Yes. Burned valves, damaged rings, head gasket failure, valvetrain faults, or piston damage can reduce Cylinder 2 compression and trigger P0302.

Why Does P0302 Only Appear During Acceleration?

Cylinder pressure increases under load. A weak coil, worn spark plug, excessive plug gap, or fuel-delivery problem may only become noticeable during acceleration or boost.

Why Does P0302 Appear Only on a Cold Start?

Possible causes include a leaking injector, intake-valve carbon deposits, coolant entering the cylinder, weak compression, or a temperature-related electrical fault.

Can Bad Fuel Cause P0302?

Contaminated or low-quality fuel usually affects multiple cylinders, but an already weak Cylinder 2 may show the problem first.

Will P0302 Clear Itself?

The Check Engine Light may turn off after several successful drive cycles if the misfire does not return. The code can remain stored or permanent until the vehicle completes the required self-tests.

Can P0302 Damage the Catalytic Converter?

Yes. Unburned fuel entering the exhaust can overheat and destroy the catalytic converter, particularly when the Check Engine Light is flashing.

Related OBD-II Misfire Codes

P0300 — Random or Multiple Cylinder Misfire
P0301 — Cylinder 1 Misfire Detected
P0302 — Cylinder 2 Misfire Detected
P0303 — Cylinder 3 Misfire Detected
P0304 — Cylinder 4 Misfire Detected
P0305 — Cylinder 5 Misfire Detected
P0306 — Cylinder 6 Misfire Detected
P0307 — Cylinder 7 Misfire Detected
P0308 — Cylinder 8 Misfire Detected
P0316 — Misfire Detected During Startup
P0352 — Ignition Coil B Primary/Secondary Circuit
P0202 — Cylinder 2 Injector Circuit Malfunction

Explore the Complete Pro Street OBD-II Code Library

P0302 is a generic powertrain diagnostic trouble code. For additional code definitions and diagnostic guides, use the Pro Street OBD-II cornerstone pages:

Remember that a diagnostic trouble code identifies the system and failure pattern detected by the vehicle. It does not give you permission to fire the parts cannon.

For P0302, begin with the scan data, verify the location of Cylinder 2, and test the spark plug and ignition coil. If the misfire stays with Cylinder 2, continue with the injector, wiring, intake system, compression, and leak-down testing until the actual cause is confirmed.

P0302 Code Explained: Cylinder 2 Misfire Detected