OBD2 Logger

OBD2 Logger turns your iPhone into a precision data logger for any modern car. Plug a Bluetooth ELM327 adapter into your vehicle's OBD2 port, pair it once, and stream live engine, hybrid, battery, and emissions data straight into per-session CSV files on your phone. No accounts. No cloud. No analytics. Your driving data never leaves your device.

LIVE READOUT
• 40+ standard SAE J1979 PIDs, automatically discovered from your car: RPM, vehicle speed, coolant temp, throttle, MAF, intake MAP, fuel trims, catalyst temperatures, and more.
• Manufacturer-specific Mode 21 PIDs on profiled vehicles — including HV pack voltage, MG1/MG2 motor torque, and battery cell-block temperatures on Toyota/Lexus hybrids.
• Values grouped by category (Engine, Hybrid, Battery, Emissions, Diagnostics) and updated every second.
• One CSV per logging session, written into the app's Files container — open it in Numbers, Excel, pandas, DuckDB, or any other tool with no preprocessing.
• Wide-table format: ISO-8601 timestamps, one column per active PID, blank cells where the ECU returned no data (no spurious forward-fill).
• Smart-stop after extended idle so you don't end up with a tail of empty rows when you forget to tap Stop.

WORKS IN THE BACKGROUND
• Keeps logging while you drive with Maps in the foreground or the screen off, using Apple's standard background location mode for trip-tracking apps. The system location indicator is shown the entire time. We don't store your location.

VEHICLE PROFILES
• Ships with three profiles: a generic Mode-01 fallback, a Toyota hybrid family profile, and a 2020 Lexus RX 450h/450hL profile validated against a real vehicle.
• VIN auto-read on connect; year, make, model, and trim pre-filled from NHTSA's free public vPIC API.
• Import any third-party profile JSON to add coverage for your car. The format is documented and human-readable.

DON'T HAVE AN ADAPTER YET?
• Tap "Try demo mode" on the second onboarding step to explore the app end-to-end with synthetic data — no hardware required.

WHAT YOU NEED
• Any Bluetooth Low Energy ELM327 adapter (Veepeak OBDCheck BLE+, vLinker MC+, OBDLink, etc. — most BLE clones work). USB-only and Wi-Fi-only adapters are NOT supported.
• A car with an OBD2 port (1996+ in the US, 2001+ in the EU).

PRIVACY
• Nothing is collected, transmitted, or stored on our servers — we don't have servers. The only outbound call the app ever makes is one VIN decode per vehicle to NHTSA's vPIC API.
• Your CSVs and vehicle records live in the app's Files container, accessible to you in the iOS Files app under On My iPhone → OBD2 Logger.
• Open source: github.com/NathanNam/obd2-logger