From a check-engine light to a clearer next step. Explore code meanings, possible symptoms, and component locations.
9,533codes in this edition
01 / POWERTRAIN02 / CHASSIS03 / BODY04 / NETWORK
YOUR VEHICLEGeneral OBD-II referenceAdd vehicle details for your reference and repair-information searches.
TRY A CODE
CODE LIBRARY
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PARTS & SYMPTOMS · OFFLINE REFERENCE
Explore the engine. Recognize the signs.
Search 110 engine components by name, abbreviation, symptom, or related code. Wear, contamination, leaks, and electrical failures can cause similar symptoms.
TRY A PART
BROWSE ENGINE COMPONENTS
START WITH WHAT YOU NOTICE
Find an issue. Compare the possibilities.
27 offline observation guides connect visible signs, sounds, and running problems to possible causes and appropriate confirmation checks. These are general guides, not a diagnosis of your vehicle.
COMMON OBSERVATIONS
READ THE SIGNAL
What your scan tool is telling you.
01
Find the diagnostic port
On most OBD-II cars, the 16-pin diagnostic connector is beneath the driver’s side dashboard. Use the owner’s manual if it is hidden behind a cover. This reference covers OBD-II, generally US passenger cars and light trucks from model year 1996 onward; older and other-market vehicles can differ.
02
Read and record
Follow your scanner’s instructions. Save the exact code, any suffix, its status (pending, confirmed or permanent), and freeze-frame data before clearing anything. Clearing codes can erase diagnostic information and reset emissions readiness monitors.
03
Understand the letters
P = powertrain, including engine and transmission. C = chassis. B = body. U = network communications.
Generic and manufacturer-controlled ranges coexist. Do not assume the same definition for every code across every manufacturer.
04
Find the actual cause
Match the code to the exact year, make, model and engine. Use the factory diagnostic procedure and wiring diagram. A circuit-low code, for example, can involve wiring or power supply as well as the component.
A flashing check-engine light, severe shaking, overheating or oil-pressure warning needs prompt attention. Stop safely and follow the owner’s manual.
KNOW YOUR REFERENCE
Broad coverage. Clear boundaries.
What is included
This edition contains 9,533 community-maintained OBDex records: 7,330 powertrain, 635 chassis, 339 body, and 1,229 network entries. Data snapshot: October 15, 2026. These counts describe this dataset, not the number of codes supported by your vehicle.
Definitions, possible symptoms and possible causes are community reference data. They have not been independently verified against every manufacturer. Some entries are general or limited.
This is not every diagnostic code ever made. Manufacturer-specific definitions, legacy OBD-I flash codes, heavy-duty J1939 fault codes, and extended failure-byte definitions are not comprehensively included.
Generic component locations are orientation guidance. Vehicle details saved here do not verify compatibility or provide VIN-specific component positions. The Parts & symptoms tab covers 110 engine component types, not every part or vehicle. It is a maintenance reference, not a replacement-part fitment or shopping catalog. The Symptom lookup contains 27 general observation guides; it does not diagnose a vehicle or establish a failed part. Unlisted codes are never assigned a guessed definition.
Primary references
Use official manufacturer repair information for the final definition, connector, bank and cylinder identification, test procedure, and mounting location.
Saved codes and the vehicle label stay in this browser’s local storage. No account or scanner connection is required. This page cannot read the car, confirm a diagnosis, or clear codes.
External research links open a search with the code and your vehicle details. They do not provide an integrated factory repair database.