P0302 OBD2 Code Guide
P0302 is a engine diagnostic trouble code. Use this hub to understand the plain meaning, the first checks to run, and which vehicle-specific guides may be more useful before replacing parts.
Cylinder 2 Misfire Detected
Code P0302 indicates that the Powertrain Control Module (PCM) has detected a misfire condition specifically in cylinder #2. A misfire occurs when an engine cylinder fails to properly ignite the air/fuel mixture, leading to a loss of power, rough running, and increased emissions. The PCM monitors crankshaft speed fluctuations and exhaust gas oxygen levels to identify misfires. When a significant fluctuation or oxygen imbalance is detected repeatedly in cylinder 2, the P0302 code is set, and the Check Engine Light (CEL) will illuminate, often flashing if the misfire is severe enough to cause catalytic converter damage.
Code verification standard
P0302 is published with SAE J2012 / ISO 15031-6 code structure plus OBD2 P0302 diagnostic context.
First checks
- - Read all stored and pending codes before clearing anything.
- - Save freeze-frame data so you know speed, load and temperature when the code set.
- - Inspect wiring, connectors, fuses, hoses and obvious leaks tied to the named system.
- - Compare live data against realistic values before buying sensors or modules.
- - Clear the code only after repair and complete a drive cycle to confirm it does not return.
P0302 diagnostic path
- 1Verify Code and Check for Other Codes: Connect an OBD-II scanner to confirm P0302 and check for any other related codes (e.g., fuel trim codes, sensor codes). Record freeze frame data. Clear codes and test drive to see if P0302 returns immediately.
- 2Inspect Ignition System Components for Cylinder 2: Visually inspect the spark plug, ignition coil, and spark plug wire (if applicable) for cylinder 2. Look for cracks, carbon tracking, oil fouling, or corrosion. Swap the ignition coil and spark plug from cylinder 2 with a known good cylinder (e.g., cylinder 1 or 3) and retest. If the misfire moves to the new cylinder, the swapped component is faulty.
- 3Check Fuel System for Cylinder 2: Perform a fuel injector balance test or listen to the cylinder 2 fuel injector with a stethoscope to confirm it's clicking. If possible, swap the fuel injector from cylinder 2 with another cylinder. If the misfire moves, the injector is faulty. Also, check fuel pressure and ensure it's within specifications.
- 4Perform Compression and Leak-Down Test: If ignition and fuel systems check out, perform a compression test and a leak-down test on cylinder 2. Low compression or excessive leak-down indicates an internal engine issue such as a faulty head gasket, bent valve, worn piston rings, or a cracked cylinder head.
- 5Inspect for Vacuum Leaks and PCM Issues: Check for vacuum leaks near cylinder 2's intake runner using a smoke machine or by spraying carb cleaner. If all other components are verified good, consider testing the PCM, though this is rare for a single-cylinder misfire.
Verify before repair
- - Replace the faulty spark plug or spark plug wire for cylinder 2.
- - Replace the ignition coil for cylinder 2.
- - Clean or replace the fuel injector for cylinder 2.
- - Repair internal engine issues (e.g., head gasket, valves, piston rings) if compression/leak-down tests indicate mechanical failure.
Vehicle-specific pages to check next
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