Symptom & fix library
What’s your car doing?
Find the symptom for what it usually means, the likely causes ranked, how urgent it is, and a typical repair range. Or describe it and start a case for your car.
67 symptom guides. Got a trouble code instead? Browse the OBD-II code library.
Engine & performance
- Check engine light is onA steady check-engine light means the car stored a trouble code — anything from a loose gas cap to a misfire.Get it checked soon
- Engine idles rough or shakes at a stopA shaky, uneven idle at a stoplight usually points to a misfire, a vacuum leak, or dirty intake components.Get it checked soon
- Engine feels down on power or goes into limp modeSudden sluggishness or a capped RPM is often the engine protecting itself after detecting a fault.Address promptly
- Engine stalls or dies while driving or idlingAn engine that cuts out at idle or stops while driving usually has an air, fuel, or idle-control problem.Address promptly
- Worse gas mileage than usualA sudden drop in MPG often traces to sensors, tires, or a fuel-mixture problem rather than the engine itself.Monitor it
- Check engine light is flashingA blinking check-engine light means an active misfire is dumping raw fuel into the exhaust — the one CEL you shouldn’t drive on normally.Address promptly
- Car hesitates or stumbles when acceleratingA pause, stumble, or flat spot when you press the gas usually means the engine is momentarily starved of fuel or air.Get it checked soon
- Car shakes or vibrates when acceleratingVibration that appears under acceleration and fades when you lift off usually points to a misfire under load, a broken engine mount, or a worn axle joint.Get it checked soon
- RPM surges or fluctuates while drivingA tachometer that bounces or surges without your foot moving points to an air-metering problem, a slipping transmission, or a torque-converter fault.Get it checked soon
- Car runs rough when cold but smooths out warmRough running for the first few minutes after a cold start usually traces to fueling that can’t keep up with cold-enrichment demands.Get it checked soon
- Engine misfire (skipping, stumbling, or a dead cylinder)A misfire means one or more cylinders aren’t burning their fuel — the codes usually name the cylinder, which makes this unusually diagnosable.Address promptly
- “Engine power reduced” warning came onThis message means the computer has deliberately limited throttle because it can’t trust what the throttle system is telling it.Address promptly
- Car jerks or bucks while drivingJerking at steady speed or under light throttle can be engine misfiring or the transmission hunting — when it happens tells you which.Get it checked soon
Starting & electrical
- Car won’t start (clicks or cranks but won’t fire)A no-start splits into two cases: the engine won’t crank (usually electrical) or cranks but won’t fire (fuel or spark).Address promptly
- Battery / charging warning light is onThe battery light usually means a charging-system problem — most often the alternator, not the battery itself.Address promptly
- Flickering lights or odd electrical glitchesDimming lights, random warnings, or electronics that misbehave often trace to the battery, alternator, or grounds.Get it checked soon
- Car won’t start and just clicksRapid clicking usually means a weak battery or bad connections; one loud click points to the starter or its solenoid.Address promptly
- Engine cranks but won’t startIf the starter spins the engine normally but it never fires, the battery is fine — the problem is fuel, spark, or a sensor.Address promptly
- Car won’t start and makes no sound at allNo click, no crank, nothing: either the whole car is dead (battery/connections) or one circuit — ignition switch, neutral safety switch, or starter feed — is broken.Address promptly
- Car starts then immediately diesAn engine that fires up and dies within seconds points to the immobilizer, idle control, fuel delivery, or a vacuum leak.Address promptly
- Car is hard to start on cold morningsSlow cranking or long cranking on cold mornings usually means an aging battery, a cold-fuel enrichment problem, or worn glow plugs on a diesel.Get it checked soon
- Battery keeps dying overnightA battery that’s dead every morning points to a parasitic drain, a battery that can no longer hold charge, or a leaking alternator diode.Get it checked soon
- Headlights flicker or dim while drivingFlickering or pulsing headlights usually mean unstable system voltage — an alternator or voltage regulator problem, bad grounds, or poor battery connections.Get it checked soon
- Key won’t turn in the ignitionA key that won’t turn is usually the steering-wheel lock binding — and if not, a worn key, a worn lock cylinder, or the shifter not fully in Park.Get it checked soon
Braking & steering
- Brakes squeal, squeak, or grindA high squeal usually means pads are due; a metallic grind means metal-on-metal and needs attention now.Address promptly
- Steering wheel or car shakes (especially when braking)A shimmy through the wheel often means warped rotors, an out-of-balance tire, or a worn suspension part.Get it checked soon
- Car pulls to one side while drivingA steady pull usually means alignment or tire pressure; a pull only when braking points to the brakes.Get it checked soon
- Brake pedal feels soft or spongyA pedal that feels mushy or travels farther than usual usually means air or a leak in the hydraulic system.Address promptly
- Brake pedal goes to the floorA pedal that sinks to the floor with little or no braking means the hydraulic system has failed — stop driving.Stop driving — get help
- ABS light is onAn ABS light means the anti-lock system has shut itself off — your regular brakes still work, but without anti-lock protection.Get it checked soon
- Steering wheel is hard to turnHeavy steering usually means the power assist has quit — low fluid, a failing pump or belt, or an electric assist fault.Address promptly
- Clunking or clicking noise when turningClicking that keeps rhythm with the wheels during turns is the classic worn CV joint; clunks point to suspension links.Get it checked soon
- Squealing noise when turning the wheelA squeal as you turn usually means the belt is slipping under power steering load or the fluid is running low.Get it checked soon
- Traction control light is onA steady traction control light means the system is disabled — often by the same wheel sensor fault that trips the ABS light.Get it checked soon
Noises & vibration
- Grinding or growling noise while drivingA grind that changes with speed often means a wheel bearing; one that changes with braking points to brakes.Address promptly
- Burning smell from the engine or ventsThe type of smell matters: burning oil, hot brakes, electrical burning, and sweet coolant each mean different things.Address promptly
- Knocking noise from the engineEngine knock ranges from harmless-sounding ping under load to a deep rod knock that means stop driving now.Address promptly
- Ticking noise from the engineA tick from the engine bay ranges from normal injector noise to low oil pressure starving the lifters — check the oil first.Get it checked soon
- Car shakes at highway speedA vibration that appears in a specific speed band — often 60–75 mph — is most often a tire balance problem.Get it checked soon
- Humming noise that gets louder while drivingA hum or drone that rises with road speed is usually a wheel bearing or cupped tires — the lane-change test tells them apart.Get it checked soon
- Squealing noise when starting the carA squeal right at startup that fades after a few seconds is almost always the serpentine belt or its tensioner.Get it checked soon
- Rattling noise under the carA metallic rattle from underneath — often at idle or over bumps — is most commonly a loose exhaust heat shield, one of the cheapest fixes in this library.Monitor it
- Clunking noise over bumpsA knock or clunk from a corner of the car over bumps points to worn suspension links — sway bar links and strut mounts lead the list.Get it checked soon
- Whining noise when acceleratingA whine that climbs with engine RPM points to the pumps and pulleys the engine drives; one tied to road speed points to the gears.Get it checked soon
Overheating & fluids
- Engine temperature runs hot or overheatsA rising temperature gauge means the cooling system isn’t keeping up — low coolant, a stuck thermostat, or a failing pump.Stop driving — get help
- Coolant leak (puddle or dropping coolant level)A green, orange, or pink puddle and a sweet smell mean coolant is escaping — a leak that can lead to overheating.Address promptly
- Oil leak or low oil pressure warningDark puddles or an oil-pressure light mean the engine is losing or not circulating oil — don’t ignore the light.Address promptly
- Transmission fluid leaking (red or brown puddle)A red or brown puddle toward the middle of the car means transmission fluid is escaping — and low fluid leads to slipping.Address promptly
- Power steering fluid leaking (whining or heavy steering)A whine when turning plus steering that feels heavy usually means the power-steering system is losing fluid.Get it checked soon
- Brake fluid leaking (puddle near a wheel or soft pedal)Clear-to-amber fluid near a wheel or under the master cylinder means the brake system is losing pressure — a genuine stop-driving problem.Stop driving — get help
- Oil pressure warning light came onThe red oil-can light means the engine isn’t seeing proper oil pressure — check the level first, and don’t drive on a lit light.Stop driving — get help
- Water dripping under the carClear, odorless water under the car is almost always normal A/C condensation — the key is confirming it isn’t coolant.Monitor it
- Milky oil on the dipstickOil that looks like a chocolate milkshake means coolant is mixing in — often a head gasket — though a little cream under the oil cap can be harmless condensation.Address promptly
Exhaust, smoke & smells
- White smoke from the exhaustThin white vapor on a cold morning is normal — thick, sweet-smelling white smoke that persists means coolant is burning in the engine.Address promptly
- Blue or gray smoke from the exhaust (burning oil)Blue-tinted smoke means the engine is burning oil — when it appears (startup vs. acceleration) tells you where the oil is getting in.Get it checked soon
- Black smoke from the exhaustBlack, sooty smoke means the engine is burning too much fuel — a rich mixture from a sensor, injector, or fuel-pressure fault.Get it checked soon
- Gas smell in or around the carA raw-fuel smell means gasoline vapor or liquid is escaping somewhere — and liquid fuel near a hot engine is a fire risk, so take it seriously.Address promptly
- Rotten egg smell from the exhaustA sulfur or rotten-egg smell means the catalytic converter isn’t processing fuel byproducts properly — often because the engine is running rich upstream.Get it checked soon
- Exhaust suddenly loud or roaringA car that suddenly got loud has an exhaust leak — a rusted muffler, broken pipe, or cracked manifold — and leaks ahead of the cabin can let fumes in.Get it checked soon
Transmission
- Transmission slips, jerks, or won’t shift smoothlyRPM that flares without speed, harsh or delayed shifts, or a slipping feeling point to a transmission problem.Address promptly
- Transmission jerks or shifts hard between gearsHarsh, clunky gear changes usually start with fluid problems or a solenoid — and are much cheaper fixed early than after the slipping starts.Get it checked soon
- Car won’t go into gear or move in driveWhether the shifter won’t move, or the car sits still in drive, the cause ranges from cheap (fluid, linkage) to serious (internal failure).Address promptly
- Shifter is stuck in parkA shifter that won’t leave park is usually the brake-shift interlock — often a failed brake light switch — rather than the transmission.Get it checked soon
- Transmission slow to engage drive or reverseA pause of a second or more between selecting gear and the car actually engaging is an early, meaningful sign of low pressure or wear.Get it checked soon
Heating & A/C
- A/C isn’t blowing cold airWarm air from the A/C usually means low refrigerant from a leak, a compressor or clutch that isn’t engaging, or a stuck blend door.Monitor it
- Heater blowing cold airA heater that blows cold often means low coolant — which can also mean an overheating risk — or a stuck blend door, clogged heater core, or bad thermostat.Get it checked soon
- Musty smell from the A/C ventsA damp, moldy smell when the A/C runs usually means mildew growing on the evaporator, a dirty cabin air filter, or a blocked condensate drain.Monitor it
Cost ranges are broad reference ranges, not quotes. For safety-related issues, have the car inspected.
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Can’t find your exact symptom?
Describe what’s happening in plain English. Every problem becomes a Case: Redline shows what the evidence supports, what’s still missing, and what to check next.
Braking grind · 2016 Toyota Camry
“Inner pad ~1 mm. Outer pad 3 mm.”
Sticking caliper / slidePossible → Supported
Worn rotor onlyPossible → Less likely
Next: check the slide pins move freely before buying parts.