P0303 on Pontiac
Cylinder 3 Misfire Detected
P0303 on Pontiac vehicles indicates cylinder 3 misfire detected. Au7o has documented this code across 1 Pontiac model — most commonly on Sunfire. This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. Typical repair costs on Pontiac range from $1,000 to $2,500, depending on the specific model and root cause.
Common Causes of P0303
- •Worn or fouled spark plug in cylinder 3
- •Failed or weak ignition coil on cylinder 3
- •Bad spark plug wire or boot (where applicable)
- •Clogged or leaking fuel injector for cylinder 3
- •Vacuum or intake air leak affecting that cylinder
- •Low compression (worn rings, burnt/leaking valve, head gasket)
- •Wiring or connector fault at the coil or injector
P0303 on Pontiac by Model
Pontiac Sunfire(1 issue)
- Sunfire 2.2L Ecotec (L61) Head Gasket / Head Crack2002-2005
The first-generation 2.2L Ecotec L61 in 2002-2005 Sunfire (and Cobalt, Cavalier, Saturn Ion) is prone to head gasket failure and cylinder head cracking — particularly if overheated once. Aluminum head warps easily. Often presents as bubbles in coolant reservoir, white smoke, and overheating.
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View P0303 across all makes →Frequently Asked Questions
What does P0303 mean on Pontiac?▼
P0303 stands for "Cylinder 3 Misfire Detected." This code means your engine's computer detected a misfire specifically in cylinder number 3 — that cylinder isn't burning its fuel-air mixture properly or completely. The computer senses misfires by watching for tiny fluctuations in crankshaft speed each time a cylinder is supposed to fire. A misfire wastes fuel, can cause a noticeable shake, rough idle or loss of power, and can flood raw fuel into the exhaust where it may overheat and damage the catalytic converter. Because the fault is isolated to one cylinder, the cause is usually something specific to that cylinder's ignition, fuel delivery, or compression. On Pontiac specifically, this code is documented across 1 model.
What causes P0303 on Pontiac vehicles?▼
Common causes on Pontiac: Worn or fouled spark plug in cylinder 3, Failed or weak ignition coil on cylinder 3, Bad spark plug wire or boot (where applicable), Clogged or leaking fuel injector for cylinder 3, Vacuum or intake air leak affecting that cylinder. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0303 on a Pontiac?▼
Repair costs on Pontiac range from $1,000 to $2,500, depending on the specific model and root cause.
Which Pontiac models have P0303 documented?▼
Au7o has documented P0303 on 1 Pontiac model: Sunfire.