P0303: Cylinder 3 Misfire Detected
Can you still drive? Not recommended if the check engine light is flashing. Driving with active misfires can destroy the catalytic converter.
What Does P0303 Mean?
Code P0303 indicates that the engine control module has detected a misfire in cylinder 3. The misfire could be intermittent or continuous and is caused by a failure in the ignition, fuel, or mechanical systems specific to that cylinder. The ECM tracks misfire counts and sets the code when the count exceeds a calibrated threshold.
Need to read your codes?
An OBD-II scanner lets you read and clear diagnostic trouble codes from your vehicle's computer. Most scanners work with any car made after 1996.
Browse OBD-II Scanners on AmazonCommon Causes
- Worn or fouled spark plug
- Failed ignition coil
- Clogged fuel injector
- Burnt exhaust valve
- Head gasket leak at cylinder 3
Symptoms
- Check engine light on or flashing
- Rough idle especially when cold
- Engine stumbling during acceleration
- Noticeable vibration
- Raw fuel smell from exhaust
Diagnostic Steps
- 1Swap ignition coil from cylinder 3 with an adjacent cylinder
- 2Inspect and replace spark plug in cylinder 3
- 3Test fuel injector resistance and spray pattern
- 4Perform compression test on cylinder 3
- 5Perform leak-down test if compression is low
- 6Check for coolant in cylinder 3 indicating head gasket failure
Recommended Parts & Tools
ignition coil
fuel injector
compression tester
Estimated Repair Cost
| Type | Estimated Cost |
|---|---|
| Total Repair Cost Range | $50 - $2000 |
| Parts Only (DIY) | $50 - $200 |
| Labor (1-3 hrs @ $100/hr) | $100 - $300 |
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Chat with AI About P0303Commonly Affected Vehicles
Related Recalls
1 Active Recall — 2026 Chevrolet Equinox
The following NHTSA safety recalls have been issued for this vehicle. Contact your dealer to check if your vehicle is affected.
EQUIPMENT:OTHER:OWNERS/SERVICE/OTHER MANUAL
General Motors has decided that certain 2027 Chevrolet Bolt EV, 2025-2026 Cadillac OPTIQ, Chevrolet Colorado, Equinox EV, GMC Canyon, 2026 Buick Enclave, Envision, Cadillac CT5, Escalade, Escalade ESV, Escalade IQ, Escalade IQL, LYRIQ, VISTIQ, Chevrolet Blazer EV, Corvette Convertible, Corvette Coupe, Corvette Convertible E-Ray, Equinox, Silverado 1500, 2500, 3500, Silverado EV, Suburban 1500, Tahoe, Traverse, GMC Acadia, Hummer EV Pickup, Hummer EV SUV, Sierra 1500, 2500, 3500, Sierra EV, Terrain, Yukon, and Yukon XL vehicles. The radio may not have been set to the correct status to download the electronic owner's manual during production. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 208, “Occupant Protection.”
Remedy: Dealers will reset the vehicle radio, which will facilitate automatic download of the electronic owner’s manual, free of charge. Owner notification letters are expected to be mailed April 13, 2026. Owners may contact GM customer service at 1-866-467-9700, Chevrolet customer service at 1-800-222-1020 or Cadillac customer service at 1-800-333-4223. The manufacturer's number for this recall is N252540430. Vehicle Identification Numbers (VINs) involved in this recall became searchable on NHTSA.gov on February 26, 2026.
Data provided by the National Highway Traffic Safety Administration (NHTSA).
Frequently Asked Questions
Why does my car shake with P0303?
When cylinder 3 misfires, it does not produce power during its combustion stroke. This creates an imbalance in the engine, causing noticeable vibration.
Can P0303 be caused by a timing issue?
Yes, incorrect valve timing due to a stretched timing chain or failed variable valve timing system can cause misfires in specific cylinders.
Community Fix Reports
Community reports are user-submitted and not verified by Auto AI Buddy. Results may vary.
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