P0302 Code: Causes, Symptoms, Diagnosis & How to Fix It
The P0302 code means Cylinder 2 Misfire Detected.
Your vehicle's powertrain control module (PCM) has detected that cylinder 2 is not firing correctly. A misfire occurs when combustion in a cylinder is incomplete or does not occur as expected.
P0302 identifies the affected cylinder, but it does not automatically identify the failed part. The cause could involve the ignition system, fuel delivery, air intake, engine compression, wiring, or other engine-management components.
The location of cylinder 2 varies by engine design, so always use the vehicle's service information to identify the correct cylinder.
P0302 Code Symptoms
Common symptoms of P0302 include:
Check Engine Light
Rough or shaking engine
Rough idle
Hesitation during acceleration
Reduced engine power
Poor fuel economy
Hard starting
Engine stalling
Unusual exhaust odor
Flashing Check Engine Light
A severe or active misfire can make the engine run noticeably rough and may affect vehicle performance.
Common Causes of P0302
Several problems can cause a cylinder 2 misfire.
1. Faulty Spark Plug
A worn, fouled, damaged, or incorrectly gapped spark plug can prevent cylinder 2 from igniting the air-fuel mixture properly.
2. Bad Ignition Coil
A weak or failed ignition coil can produce insufficient spark and cause cylinder 2 to misfire.
3. Fuel Injector Problem
A clogged, restricted, leaking, or electrically faulty fuel injector may prevent cylinder 2 from receiving the correct amount of fuel.
4. Vacuum or Intake Leak
An intake leak near cylinder 2 can create an incorrect air-fuel mixture and contribute to a misfire.
5. Low Fuel Pressure
A fuel pump, fuel-pressure regulator, filter, or other fuel-delivery problem can result in insufficient fuel.
6. Low Engine Compression
Valve problems, piston or ring damage, head-gasket issues, or other mechanical faults can reduce compression and cause a persistent cylinder misfire.
7. Wiring or Sensor Problems
Damaged ignition, injector, crankshaft, or camshaft wiring can interfere with engine control and trigger a misfire.
8. EGR or Other Engine-Control Problems
Certain EGR faults and other engine-management problems can contribute to misfire conditions.
How to Diagnose the P0302 Code
A systematic diagnosis helps prevent replacing parts unnecessarily.
1. Scan for Additional Codes
Use an OBD2 scanner to check for other stored or pending DTCs. Misfire, fuel-system, sensor, or lean-condition codes can provide important clues.
Record the freeze-frame information before clearing any codes.
2. Inspect the Spark Plug
Remove the cylinder 2 spark plug and inspect its condition. Look for fouling, excessive wear, damage, oil contamination, or an incorrect gap.
3. Check the Ignition Coil
Inspect the coil, boot, connector, and wiring. On vehicles with interchangeable coils, a useful diagnostic method is to move the cylinder 2 coil to another cylinder and see whether the misfire follows the coil.
4. Check the Fuel Injector
If the ignition system appears normal, inspect the cylinder 2 injector and its electrical connection. Depending on the vehicle, injector testing may include checking electrical operation, fuel delivery, or injector balance.
5. Check for Intake Leaks
Inspect vacuum hoses, intake components, and the intake manifold for leaks. A smoke test can help locate leaks that are difficult to see.
6. Test Engine Compression
If the misfire remains after ignition and fuel-system checks, perform a compression test. Low compression can indicate an internal mechanical problem.
7. Check Timing and Engine Sensors
If necessary, inspect camshaft/crankshaft synchronization and related sensor data. Manufacturer-specific diagnostic procedures should be followed when sensor or timing problems are suspected.
How to Fix P0302
The correct repair depends on what caused the misfire. Possible repairs include:
Replace a worn or damaged spark plug
Replace a defective ignition coil
Repair ignition wiring or connectors
Repair or replace a faulty fuel injector
Repair a vacuum or intake leak
Correct low fuel pressure
Repair damaged sensor wiring
Repair EGR-related problems when confirmed
Correct engine timing problems
Repair an internal engine problem causing low compression
After the repair, clear the DTC and perform a test drive while monitoring misfire data to confirm that P0302 does not return.
Avoid replacing the ignition coil, injector, or other components based only on the presence of P0302. The code identifies the misfiring cylinder, not necessarily the failed component.
Is P0302 Serious?
P0302 should not be ignored. A persistent misfire can affect engine performance and may damage the catalytic converter or other components.
If the Check Engine Light is flashing, the engine is shaking severely, the vehicle is losing significant power, or it is stalling, avoid continued driving and have the vehicle diagnosed promptly.
If the light is steady and the vehicle is operating normally, arrange diagnosis as soon as practical.
P0302 vs. P0301: What's the Difference?
Both codes indicate a cylinder-specific misfire, but they identify different cylinders:
Code | Meaning |
P0301 | Cylinder 1 Misfire Detected |
P0302 | Cylinder 2 Misfire Detected |
The diagnostic process is similar, but you must identify the correct cylinder and inspect its corresponding ignition, fuel, intake, and mechanical components.
P0302 vs. P0300
P0300 indicates a random or multiple-cylinder misfire without identifying one specific cylinder.
P0302 specifically identifies cylinder 2 as the cylinder where the PCM detected the misfire.
Frequently Asked Questions
Can a bad spark plug cause P0302?
Yes. A worn, fouled, damaged, or incorrectly gapped spark plug is one of the common causes of a cylinder-specific misfire.
Can a bad ignition coil cause P0302?
Yes. A defective ignition coil can prevent cylinder 2 from receiving a strong enough spark.
Can I drive with P0302?
It depends on the severity. A vehicle with a severe misfire, flashing Check Engine Light, major shaking, or power loss should not continue to be driven unnecessarily.
Does P0302 mean cylinder 2 needs repair?
Not necessarily. P0302 identifies a misfire in cylinder 2, but the actual cause could be the spark plug, ignition coil, injector, vacuum leak, fuel system, compression, wiring, or another problem.
Can low compression cause P0302?
Yes. Mechanical engine problems that reduce compression can cause a persistent cylinder 2 misfire.
