What P0302 Means
P0302 is the same fault type as P0301 — a misfire consistently detected in a single, specific cylinder — but isolated to cylinder 2 instead. The underlying causes and diagnostic approach are identical: something unique to cylinder 2's ignition, fuel delivery, or mechanical condition is preventing that cylinder from combusting properly on every cycle, while the rest of the engine runs normally. As with any single-cylinder misfire code, swapping the ignition coil or spark plug between cylinder 2 and a neighboring cylinder is typically the fastest way to confirm whether the fault lies with that component or with something specific to the cylinder's position (injector, compression, or a local vacuum leak). One detail worth checking early: on engines where cylinder 2 sits in a position more exposed to heat, vibration, or moisture (depending on the specific engine layout), that cylinder's ignition components can sometimes wear or fail slightly ahead of others, which is part of why a single-cylinder pattern doesn't necessarily mean anything unusual is happening — it's often simply the first component to reach the end of its service life.
Common Causes
- Worn, fouled, or damaged spark plug in cylinder 2
- Failing ignition coil serving cylinder 2
- Clogged, leaking, or electrically failed fuel injector on cylinder 2
- Low compression in cylinder 2 from worn piston rings or a valve sealing issue
Symptoms You Might Notice
- Check Engine Light on, flashing if the misfire is severe or sustained
- Noticeable rough idle or engine shake
- Hesitation or stumbling under acceleration
- Reduced power and fuel economy
What to Check First
- 1
Inspect and replace the spark plug in cylinder 2 if worn, fouled, or improperly gapped
- 2
Swap the ignition coil between cylinder 2 and a neighboring cylinder, clear the code, and see whether the misfire follows the coil to confirm or rule it out
- 3
Check the cylinder 2 fuel injector using resistance or balance testing if ignition components test fine
- 4
Perform a compression or leak-down test specifically on cylinder 2 if fuel and ignition components both check out
- 5
Check cylinder 2's spark plug gap against factory specification even if the plug looks otherwise healthy, since an incorrect gap alone can cause a consistent misfire without any visible fouling or damage
Frequently Asked Questions
Do I need to fix P0302 immediately?
If the Check Engine Light is flashing, yes — that indicates an active misfire severe enough to risk catalytic converter damage. A steady (non-flashing) light still warrants prompt attention, but doesn't require stopping the car immediately.
Why is it always the same cylinder misfiring?
A consistent single-cylinder misfire points to something specific to that cylinder's hardware — its spark plug, coil, injector, or internal mechanical condition — rather than a system-wide issue affecting the whole engine equally, which is what makes single-cylinder codes more straightforward to isolate.
Could this be the same root cause as a P0300 I had before?
Possibly — if a prior P0300 wasn't fully resolved, or if a component like an aging coil pack has now progressed to consistently affecting one particular cylinder, it can evolve from a random multi-cylinder pattern into a specific single-cylinder code like P0302.
Could a bad ignition coil pack affect multiple cylinders including cylinder 2?
On engines that use a shared coil pack rather than individual coil-on-plug units, yes — a single failing coil pack can cause a misfire pattern that looks isolated to one cylinder even though the root cause is a shared component, which is worth keeping in mind on older or non-coil-on-plug engine designs.
Reviewed by Emmanuel Erere, Auto Mechanic. Causes and diagnostic steps checked for workshop accuracy.