Summary
P0302 means the PCM detected repeated misfires in cylinder 2. The diagnostic approach is identical to any single-cylinder misfire: check spark plug, ignition coil, and fuel injector for that cylinder. The coil-swap test is the fastest way to isolate the cause — swap cylinder 2's coil with another cylinder, clear codes, and drive. If the misfire moves, replace the coil ($20–$80). If it stays, check the plug and injector.
Severity: Moderate to High — misfires damage catalytic converters
Safe to drive: Not recommended
Repair cost: $20–$500 depending on cause
DIY difficulty: Easy to Moderate
What does P0302 mean?
The PCM detected that cylinder 2 is misfiring more frequently than its threshold allows. The detection method is the same as P0301 — crankshaft speed variation at the point in the firing order where cylinder 2 should contribute. The code points directly to cylinder 2 as the problem cylinder.
Cylinder numbering varies by manufacturer and engine layout. On inline 4-cylinders, cylinder 2 is usually the second from the timing-belt/chain end. On V6/V8 engines, cylinder 2 can be on either bank — consult your service manual.