OBD2 Logger vs OBD2 Car Diagnostics

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

OBD2 Car Diagnostics puts a professional-grade fault code reference and vehicle maintenance tracker right in your pocket. Whether your check engine light just came on or you want to stay ahead of routine service, this app gives you the clarity you need. INSTANT DTC LOOKUP Search thousands of OBD2 diagnostic trouble codes by code number, description, or vehicle system. Each code entry shows the affected system, plain-English description, and a severity rating — Critical, High, Medium, or Low — so you know exactly how urgent the issue is. FILTER BY SYSTEM AND SEVERITY Quickly narrow results by vehicle system (engine, transmission, ABS, airbag, EVAP, and more) or by severity. Save codes you care about with a single tap and review them anytime in the Saved tab. MULTI-VEHICLE GARAGE Add all your cars, trucks, or motorcycles. Each vehicle shows its current odometer reading and a colour-coded maintenance health ring at a glance. Track make, model, year, and mileage for every vehicle in one place. MAINTENANCE REMINDERS Set odometer-based service reminders for oil changes, tyre rotations, brake inspections, air filters, and more. The Dashboard immediately surfaces any service that is due or overdue so nothing slips through the cracks. SERVICE HISTORY AND COST TRACKING Log every service visit with date, odometer, cost, and notes. View running totals per vehicle and share a full service report as plain text whenever you need it for insurance, resale, or your own records. Key features: - Offline DTC database — no internet connection required - Severity ratings: Critical, High, Medium, Low - Filter by category and severity simultaneously - Save and manage fault codes per vehicle - Odometer-based maintenance reminders - Full service log with cost tracking - Share vehicle reports in plain text - Dark mode support