Check Engine Light Flashing
Why a flashing check engine light is urgent and what to do next.
UrgentAutomotive troubleshooting
Diagnose car symptoms before you replace parts.
Start with what the car is doing. Check urgency, likely causes, safe next steps, and what to tell a mechanic.
Symptom first
Safety check
Likely causes
Mechanic notes
Urgent guides
Burning Smell From Car
How to triage burning rubber, oil, electrical, and clutch smells from a vehicle.
UrgentCar Overheating
What to do when the temperature gauge rises and how to narrow down cooling system causes.
UrgentBrake Pedal Feels Soft
Why a soft or spongy brake pedal should be treated as a safety issue.
UrgentCar Smells Like Gas
How to treat fuel smells from the cabin, engine bay, or after refueling.
UrgentCoolant Leaking Under Car
How to identify coolant leaks and decide whether the car is safe to drive.
UrgentStart with the symptom
Car Won't Start
A practical guide to the most common reasons a car will not start, from battery issues to fuel and ignition faults.
CautionCar Cranks But Won't Start
How to narrow down a normal-cranking no-start into fuel, spark, air, compression, or sensor problems.
CautionClicking Noise When Starting
What a single click or rapid clicking usually means when you try to start a car.
LowCheck Engine Light Flashing
Why a flashing check engine light is urgent and what to do next.
UrgentCheck Engine Light On But Car Runs Fine
Why a steady check engine light can still matter even when the car feels normal.
CautionCar Shakes When Accelerating
Common causes of vibration under acceleration, from misfires to axle and mount problems.
CautionCommon OBD-II codes
P0300: Random or Multiple Cylinder Misfire
P0300 means the engine computer detected misfires that are not limited to one cylinder.
High if the check engine light is flashingP0171: System Too Lean Bank 1
P0171 means the engine computer is adding fuel because it sees too much air or not enough fuel on bank 1.
ModerateP0420: Catalyst System Efficiency Below Threshold
P0420 means the catalytic converter is not storing oxygen as expected, or the sensor data makes it appear that way.
Moderate unless drivability is poorP0455: Large EVAP System Leak Detected
P0455 means the evaporative emissions system cannot hold pressure or vacuum during a leak test.
Low to moderateP0128: Coolant Temperature Below Thermostat Regulating Temperature
P0128 usually means the engine is warming up too slowly or not reaching the expected operating temperature.
ModerateP0135: Oxygen Sensor Heater Circuit Bank 1 Sensor 1
P0135 means the upstream oxygen sensor heater circuit is not working as expected.
ModerateP0301: Cylinder 1 Misfire Detected
P0301 means the engine computer detected a misfire on cylinder 1.
High if the light is flashingP0302: Cylinder 2 Misfire Detected
P0302 means cylinder 2 is misfiring often enough for the computer to flag a fault.
High if the light is flashingP0303: Cylinder 3 Misfire Detected
P0303 indicates a misfire isolated to cylinder 3.
High if the check engine light flashesParts and systems to understand
Battery
The battery stores electrical energy for starting and stabilizes voltage for the vehicle's electronics.
Provides high current to the starter and powers modules before the engine is running.Starter Motor
The starter motor turns the engine fast enough for combustion to begin.
Uses battery power through a solenoid to crank the engine.Alternator
The alternator recharges the battery and powers the electrical system once the engine is running.
Converts engine rotation into electrical output.Spark Plugs
Spark plugs ignite the air-fuel mixture inside gasoline engine cylinders.
Create the spark needed for combustion at the correct time.Ignition Coils
Ignition coils turn low battery voltage into the high voltage needed to fire spark plugs.
Supply spark energy to one or more cylinders.Oxygen Sensors
Oxygen sensors monitor exhaust oxygen so the engine computer can adjust fuel mixture and catalyst checks.
Help control fuel trim and emissions monitoring.Avoid replacing parts blindly
Safety firstKnow when to stop, tow, or drive gently.
Codes are cluesDo not replace parts blindly from one code.
Mechanic handoffBring better notes and better questions.