Diagnose your car problem.
Pick a system below, enter an OBD code, or search by symptom. Every guide includes ranked causes, step-by-step tests, and fixes.
What system is affected?
AC & Climate
6 issuesAir conditioning, heating, and climate control systems including the compressor, blower motor, refrigerant, and cabin air filter.
Explore ac & climate problems →Brakes
108 issuesYour brakes are the most critical safety system on your vehicle. Any brake issue should be diagnosed and fixed promptly — never ignore warning signs.
Explore brakes problems →Cooling
119 issuesThe cooling system keeps your engine from overheating. A failing thermostat, leaking coolant, or broken water pump can cause irreversible engine damage in minutes.
Explore cooling problems →Electrical
92 issuesModern vehicles rely on dozens of electrical systems. Battery, alternator, and wiring issues can leave you stranded or cause cascading failures throughout the car.
Explore electrical problems →Engine
264 issuesEngine problems range from minor annoyances to serious failures. Catching them early prevents expensive damage and keeps you safe on the road.
Explore engine problems →Suspension
70 issuesSuspension and steering problems affect how your car handles, brakes, and wears tires. Worn components can compromise safety and lead to rapid tire wear.
Explore suspension problems →Transmission
79 issuesTransmission repairs are among the most expensive in automotive service. Early diagnosis of slipping, rough shifts, or fluid leaks can save thousands of dollars.
Explore transmission problems →Have a check engine or OBD code?
Enter any P, B, C, or U code for an instant diagnosis.
Most diagnosed problems
Check Engine Light After Oil Change
A check engine light after oil change typically signals a loose oil cap, incorrect oil type, or a disturbed sensor rather than a serious engine problem. Most causes are simple fixes you can handle yourself in minutes.
Check Engine Light Goes on and Off
A check engine light goes on and off when your engine's diagnostic system detects an intermittent fault—meaning the problem isn't constant. This is actually more common than a permanently lit light and often points to sensor issues, loose connections, or fuel system problems that come and go.
Check Engine Light Cold Weather
A check engine light cold weather problem is one of the most common issues mechanics see in winter months, triggered by temperature-sensitive sensors and fuel mixture changes. Cold temperatures can expose underlying problems with your engine's emissions or ignition systems that aren't noticeable in warmer weather.
Engine Ticking After Oil Change
Engine ticking after oil change is often caused by incorrect oil viscosity, air in the oil system, or a faulty oil filter. Most cases are preventable with proper oil selection and filter installation.