What does your check engine code mean?
Look up any OBD2 diagnostic code for your car. Get plain-English explanations, common causes, symptoms, repair costs, and whether it's safe to keep driving— specific to your make and model year.
How it works
Read your code
Use a $25 OBD2 scanner or visit any auto parts store — they read codes free. You'll get a code like P0420 or P0171.
Look it up here
Type your code above, or search by make, or browse by category. Every code page explains what it means in plain English.
Know what to do
See the most likely causes, what it costs to fix, and whether it's safe to keep driving before you call a shop.
Most searched codes
View all 58 codes →Browse by make
All 56 makes →Not sure if it's safe to keep driving?
Some codes are fine to drive with for days; others mean pull over immediately. Our driving safety guides give you a straight answer for the most common warning lights and codes—with specific signs to watch for and when to call a tow.
View driving safety guides →What is an OBD2 code?
OBD2 (On-Board Diagnostics II) is a standardized system that every car sold in the United States after 1996 is required to have. When your car's computer detects a problem—with the engine, transmission, emissions system, or sensors— it stores a fault code and turns on the check engine light.
Codes follow a standard format: a letter identifies the system (P for powertrain, B for body, C for chassis, U for network communications), followed by four digits that pinpoint the fault. Generic codes (P0xxx) are the same across all makes; manufacturer-specific codes (P1xxx) vary by brand.
A $20–$40 Bluetooth OBD2 scanner can read codes from your phone. Most auto parts stores will also read them for free. Once you have the code, look it up here to understand exactly what it means for your specific vehicle.
Frequently asked questions
What is an OBD2 code?
An OBD2 (On-Board Diagnostics II) code is a standardized fault code your car's computer stores when it detects a problem. Any vehicle sold in the US after 1996 uses OBD2. Codes start with a letter (P for powertrain, B for body, C for chassis, U for network) followed by four digits. A code reader or scanner retrieves them—most auto parts stores will read them for free.
What does a check engine light mean?
A check engine light means your car's computer has detected a fault and stored at least one OBD2 code. A steady light usually means a non-urgent issue you can drive to a shop with. A flashing check engine light means an active misfire that can damage your catalytic converter—reduce speed and get it checked immediately.
Is it safe to drive with the check engine light on?
It depends on the code. Many codes—like an EVAP leak or a sensor fault—are safe to drive with for a few days. Others, like a misfire (P0300) or low oil pressure, require stopping immediately. Look up your specific code to get a definitive answer.
How do I read OBD2 codes without a scanner?
You need a code reader or OBD2 scanner to read stored codes. Basic Bluetooth scanners cost $20–$40 and work with free smartphone apps. Most auto parts chains (AutoZone, O'Reilly, Advance Auto) will read your codes for free in the parking lot.