What does the first letter of an OBD2 code mean?

It names the computer that stored the code: P is powertrain (engine, transmission, emissions), C is chassis (brakes, steering, suspension), B is body (airbags, comfort systems) and U is the communication network between modules.

What is the difference between a generic and a manufacturer-specific code?

The second character decides it. A 0 means the definition comes from the SAE standard and means the same thing on any vehicle; a 1 means the carmaker defined it themselves, so you need their documentation to read it.

Can I keep driving with a check engine light on?

A steady light usually means it is safe to drive to a workshop, though emissions and fuel economy may suffer. A flashing light means an active misfire dumping raw fuel into the catalytic converter — stop driving, because a converter is far more expensive than the plug or coil that caused it.

Does a P0420 code always mean I need a new catalytic converter?

No. P0420 says the downstream oxygen sensor is tracking the upstream one too closely. A tired converter is the usual cause, but an exhaust leak before the sensor, a lazy sensor or a long-running rich condition produce the same reading.

How do I know which cylinder is misfiring?

The last two digits give it: P0301 is cylinder 1, P0302 is cylinder 2 and so on, while P0300 means the misfire moved around or hit several cylinders at once.

OBD2 Code Lookup

Type a check-engine code and read what the letter, the digits and the fault number actually mean — plus the causes worth checking first.

OBD2 Code Lookup runs entirely in your browser. The code you type is decoded on your device and never uploaded.

Open the VIN Decoder

Об инструменте OBD2 Code Lookup

OBD2 Code Lookup reads a trouble code the way a technician does — by its structure. The first character names the computer that stored it: P for powertrain, C for chassis, B for body, U for the network between modules. The second digit says whether the definition comes from the SAE standard, which means the same thing on every make, or from the carmaker's own list. The third narrows it to a subsystem, and the last two identify the specific fault. That decode works for every code, including manufacturer codes no public list covers. On top of it sits a table of the codes people actually search for, each with what it means and the causes worth checking before spending money.

Возможности

Structural decode of any valid code, generic or manufacturer-specific
Plain-English meaning for the most common powertrain, chassis, body and network codes
Likely causes listed most common first
Tells you when a code is defined by the carmaker rather than the standard
Handles hybrid codes with hex subsystem characters such as P0A80
Suggests close matches when a code is mistyped
Copyable summary for a repair log or a quote
Runs entirely on your device

Как использовать OBD2 Code Lookup

Read the code from your scan tool or app
Type it in — the case and any dashes do not matter
Read the breakdown: system, standard or manufacturer, subsystem, fault
Work down the likely causes before replacing parts

Пример

Ввод

P0420

Результат

Powertrain · Generic (SAE) · Auxiliary emission controls
Catalyst system efficiency below threshold (bank 1)

The 4 in the third position places it in the emission-control subsystem.

Частые ошибки и устранение неполадок

The code has no definition here. — A second digit of 1 means the carmaker defined it, so no universal list can decode it. The structural breakdown still tells you which computer set it and which subsystem it belongs to — pair that with a make-specific manual.
The light came back after clearing the code. — Clearing a code only resets the lamp and the readiness monitors. If the fault is still present the monitor re-runs, fails and sets it again — usually within a drive cycle or two.
Several codes appeared at once. — Diagnose the lowest-numbered or most fundamental one first. A crank sensor or misfire fault sets a cascade of downstream codes, and fixing the root often clears all of them.

Часто задаваемые вопросы

What does the first letter of an OBD2 code mean?: It names the computer that stored the code: P is powertrain (engine, transmission, emissions), C is chassis (brakes, steering, suspension), B is body (airbags, comfort systems) and U is the communication network between modules.
What is the difference between a generic and a manufacturer-specific code?: The second character decides it. A 0 means the definition comes from the SAE standard and means the same thing on any vehicle; a 1 means the carmaker defined it themselves, so you need their documentation to read it.
Can I keep driving with a check engine light on?: A steady light usually means it is safe to drive to a workshop, though emissions and fuel economy may suffer. A flashing light means an active misfire dumping raw fuel into the catalytic converter — stop driving, because a converter is far more expensive than the plug or coil that caused it.
Does a P0420 code always mean I need a new catalytic converter?: No. P0420 says the downstream oxygen sensor is tracking the upstream one too closely. A tired converter is the usual cause, but an exhaust leak before the sensor, a lazy sensor or a long-running rich condition produce the same reading.
How do I know which cylinder is misfiring?: The last two digits give it: P0301 is cylinder 1, P0302 is cylinder 2 and so on, while P0300 means the misfire moved around or hit several cylinders at once.

Связанные инструменты

VIN-декодер — Расшифровывает 17-значный VIN и проверяет контрольную цифру.
Калькулятор размера шин — Расшифруйте размер шины и сравните диаметр и погрешность спидометра.
Калькулятор объёма двигателя — Объём в см³, литрах и куб. дюймах из диаметра и хода.
Калькулятор Расхода Топлива — Рассчитайте MPG, L/100km и km/L по расстоянию и топливу.
Калькулятор степени сжатия — Статическая, динамическая и наддувная степень сжатия.
Конвертер расхода топлива — Переводит MPG, л/100км и км/л, со стоимостью поездки.