OBD2 code lookup
Read the code, then fix the car
Type the code your scanner shows. See what each character means, how urgent it usually is, and what to check before you buy a part.
Start from the warning light
Pick the lamp on your dashboard. Each one leads to the codes, tests and tools that go with it.
- Check engineP codesEngine and emissions fault. Flashing means misfire.
- ABSC codesAnti-lock brakes off. Normal brakes still work.
- Airbag / SRSB codesAirbags may not deploy in a crash.
- Tire pressureTPMSLow tire or a sensor the car cannot hear.
- Battery / chargingChargingCharging system not keeping up.
- NetworkU codesModules not talking to each other.
Common codes
The codes people look up most, each with causes in checking order and what to test first.
- U0101Fix soonNo communication with transmission module
- U0100Stop drivingNo communication with engine computer
- U0001Fix soonCAN bus communication code
- P2263Fix soonTurbo boost performance problem
- P0705Fix soonTransmission range sensor fault
- P0606Fix soonEngine computer fault code
- P0496Fix soonEVAP purge flow code
- P0456Drive carefullyEVAP very small leak
- P0455Drive carefullyLarge EVAP leak code
- P0449Drive carefullyEVAP vent valve circuit fault
- P0446Drive carefullyEVAP vent valve code
- P0442Drive carefullySmall EVAP leak
Browse by topic
From choosing a scan tool to passing an emissions test.
- Choosing a scan toolCode readers, DIY scan tools and pro tablets: what each level can read, reset and test.14 notes · 15 gear guides
- Engine and emissions codes (P0)Powertrain codes behind the check engine light: fuel trim, misfires, catalyst and EVAP.37 notes · 0 gear guides
- ABS, airbag and network codes (C, B, U)Chassis, body and network codes that a basic code reader cannot see.5 notes · 1 gear guide
- TPMS, battery and service resetsTire sensor relearns, battery registration, oil service and brake service modes.3 notes · 3 gear guides
- Bidirectional tests and codingCommanding parts on and off, adaptations and module coding with a bidirectional scan tool.6 notes · 4 gear guides
- Clear codes and pass inspectionWhen clearing a code is safe, readiness monitors and getting ready for an emissions test.3 notes · 0 gear guides
Tools and reference
Decoders and readers that do the working out for you.
Scan tool guides
Narrow guides to one kind of scan tool, compared by what the listings state.
- Best XTOOL scanners: D5, D6, D7 and D8 series compared
- Best wireless Bluetooth scan tools with a tablet
- Best TPMS relearn and sensor programming tools
- Best Topdon scanners: ArtiDiag, AD and Phoenix lines compared
- Best scan tools with ECU coding for module replacement and setup
- Best scan tools for Volkswagen and Audi owners
- Best scan tools for Toyota and Lexus: brand editions vs all-makes
- Best scan tools for Mercedes-Benz owners
- Best scan tools for Jeep, Dodge, Ram and Chrysler
- Best scan tools for Honda and Acura owners
- Best scan tools for GM: Chevy, GMC, Buick and Cadillac
- Best scan tools for BMW and Mini: battery registration and coding
- Best professional diagnostic tablets for a home garage or small shop
- Best OBD2 scanners for DIY mechanics who fix their own cars
- Best OBD2 scanners for ABS and airbag (SRS) codes
- Best motorcycle diagnostic scanners
How-tos and explainers
- XTOOL D8 vs Autel MK900XTOOL D8 vs Autel MK900BT compared on listing facts: ECU coding, active tests, resets, wireless VCI, topology and protocols, plus a verdict on who buys which.
- XTOOL D7 vs Autel MK808SXTOOL D7S vs Autel MK808S compared on listing facts: ECU coding, active tests, resets, protocols and updates, with a clear verdict on who should buy which.
- Why is my check engine light on? The common causes in orderWhy is your check engine light on? The most common causes from a loose gas cap to misfires, what the light means, and how to find the real reason with a scanner.
- Where is the OBD2 port? Finding the 16-pin connectorWhere is the OBD2 port? On most cars it is under the dash on the driver side near the steering column. Common spots and fixes if a scanner will not power up.
- What ECU coding means and when a DIYer needs itWhat ECU coding is, how it differs from programming and adaptations, which repairs need it, and what kind of scan tool a DIYer needs to do it safely.
- What is a bidirectional scan tool and do you need oneA bidirectional scan tool sends commands to your car to run active tests and relearns, not just read codes. What it does, examples, and who actually needs one.