Car problem finder
Pick a symptom to see the likely causes, the checks to run and the tools you need — then start the interactive diagnostic to narrow it down.
Car will not start
The engine turns or clicks but will not fire. The cause is usually battery, starter, fuel or ignition — tested in a precise order.
See causes & checks →Engine overheats
Overheating is a warning you must not ignore. Find the cause before it damages the engine.
See causes & checks →Black smoke from the exhaust
Black smoke is unburned fuel — the mixture is too rich.
See causes & checks →White smoke from the exhaust
White smoke can be harmless condensation — or serious coolant burning.
See causes & checks →Loss of power
The car feels flat. Power loss usually comes from boost, fuel, ignition or a dragging brake.
See causes & checks →Vibration while driving
Vibration tells you where to look by when it happens: at speed, braking, idling or accelerating.
See causes & checks →Check engine light on
The light means the ECU stored a code. Steady is usually sensor/emissions; flashing is a severe misfire.
See causes & checks →High fuel consumption
A sudden jump in consumption usually has a physical cause; a gradual rise is often maintenance.
See causes & checks →Weak or spongy brakes
Never delay on brakes. A soft pedal, sinking pedal or long stopping distance needs attention now.
See causes & checks →Air conditioning not cooling
The AC not cooling usually points to gas level, the compressor clutch, or airflow.
See causes & checks →Hard starting / long cranking
Long cranking means the engine needs more of something: fuel pressure, spark, battery or compression.
See causes & checks →Oil pressure light on
The oil pressure light is one of the few you must never ignore. Stop safely and check the level before driving on.
See causes & checks →Rough or unstable idle
A rough or hunting idle points to a misfire, a vacuum leak or idle control - narrow it down by when it happens.
See causes & checks →Blue smoke from the exhaust
Blue smoke is burning oil. When you see it tells you whether it is the valve seals, the rings or the turbo.
See causes & checks →ABS warning light on
A lit ABS light means the anti-lock braking system is disabled - normal braking usually still works, but get it checked.
See causes & checks →Battery keeps going flat
A battery that drains overnight usually means a parasitic draw, a weak battery or a charging fault.
See causes & checks →Transmission slipping
Slipping, flaring or delayed shifts usually come from fluid condition, solenoids or internal wear.
See causes & checks →Battery / charging warning light
The charging light means the alternator is not keeping the battery full. Test the voltage before it leaves you stranded.
See causes & checks →Heater not blowing hot
No heat can be as simple as a clogged cabin filter, or as serious as a head gasket. Narrow it down by temperature and airflow.
See causes & checks →Clunk / knock over bumps
A clunk over bumps tells you a lot by when and where it happens: front, rear, turning or braking.
See causes & checks →Rotten egg smell / P0420
A sulfur smell or a P0420 code points to the catalytic converter or the mixture feeding it. Fix the cause before replacing the cat.
See causes & checks →EGR fault / stumble at cruise
A sticking or clogged EGR valve causes a stumble at light throttle, rough idle and pinging - often with a P0401/P0402 code.
See causes & checks →Not sure where to start?
Use the interactive diagnostic — it asks targeted questions and ranks the likely causes for you.