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Symptom Diagnosis

What is your car doing? Pick a symptom below and see the most likely causes, what to check first, and the OBD codes that match. 22 symptoms explained in plain words.

No symptoms match that search. Try a word like "brake", "smell" or "start".

Noises

Grinding noise when brakingYou hear a loud metal-on-metal grinding sound every time you press the brake pedal. The sound usually gets wor…High Engine knocking soundYou hear a metallic knocking or pinging sound from the engine, often when you accelerate or drive uphill. The …High Squealing belt noiseYou hear a high-pitched squeal from under the hood, usually loudest on a cold start or when you turn the steer…Medium Clicking noise when turningYou hear a steady clicking or popping sound from the front of the car when you turn the steering wheel, and th…Medium

Smells

Burning smellYou smell something burning, like hot oil or burning rubber, coming from the engine or through the vents. The …High Gasoline smellYou smell raw gasoline inside or around the car, even when you are not at a gas station. The smell may be stro…High Rotten egg smellYou smell rotten eggs or sulfur coming from the exhaust, especially when you accelerate. The smell is sharp an…Medium

Leaks

Oil leak under the carYou find dark brown or black spots on the ground where you park, and the oil level on the dipstick keeps dropp…Medium Coolant leak (or sweet smell)You find a green, pink, or orange puddle under the car, or you smell a sweet syrup-like odor from the engine. …High Transmission fluid leakYou find red or pink fluid on the ground under the middle of the car, and the transmission starts shifting lat…Medium

Dashboard lights

Check engine light onThe check engine light on the dashboard stays on while you drive. The car may run fine, or it may feel rough, …Medium Oil pressure light onThe oil can symbol on the dashboard lights up while the engine is running. This means the engine may not be ge…High Battery light onThe battery symbol on the dashboard lights up while you drive. The car is running on the battery alone, and it…High ABS light onThe ABS warning light on the dashboard stays on. Your normal brakes still work, but the anti-lock system may n…Medium Tire pressure light onThe tire pressure warning light (an exclamation mark inside a tire shape) stays on. One or more tires may be l…Low

Won't start

Cranks but won't startYou turn the key and the engine cranks normally, turning over and over, but it never catches and starts.…High No crank, or one click, when you turn the keyYou turn the key and nothing happens, or you hear a single loud click and the engine does not turn over at all…High

Shaking & vibration

Shaking or vibrationThe car shakes or vibrates while you drive, at idle, or at highway speed. The steering wheel, the seat, or the…Medium

Overheating

Engine overheatingThe temperature gauge climbs into the red, or you see steam and smell hot coolant from under the hood. The hea…High

Fuel economy

Poor fuel economyYour car is using more gas than it used to, and you have to fill up more often, even though your driving has n…Low

Stalling

Engine stallsThe engine shuts off by itself while you drive or while you wait at a light, and you have to restart it. It ma…High

Shifting problems

Hard or rough shiftingThe transmission shifts hard, jerks, or clunks when it changes gears, instead of shifting smoothly like it use…Medium

Not repair advice. A symptom alone is not a diagnosis — several parts can cause the same noise, smell or leak. Use the causes below as a starting point, then confirm with a scan tool and have the repair done by a qualified technician.

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