Your check engine light is data. OBDecode decodes it instantly, cross-referencing TSB records, NHTSA recalls, and pattern failures for your exact vehicle — the depth a shop charges $150 just to look up.
01
Enter Your Vehicle
VIN or manual entry — year, make, model, engine, mileage. Tap the camera icon to scan your VIN barcode. The more context, the sharper the result.
02
Add Codes & Symptoms
Describe what the vehicle is doing and when. Add fault codes. OBDecode cross-references TSBs and may ask follow-up questions to sharpen diagnosis before showing fixes with full repair steps.
03
Get Your Report
Technical briefing, diagnostic flowchart, probable fixes with step-by-step repair instructions, NHTSA recall check, and PDF export — depth a shop charges for, in seconds.
04
Or Let It Guide You
With an OBD2 dongle connected, GUIDED DIAG walks a specific symptom one step at a time — find the computers, read their fault codes, get a plain-language answer. ECU SELECT → CAPABILITY REPORT first tells you exactly what your dongle and car can and cannot do. Both are read-only.
⬡ RECENT DIAGNOSES▼
⬡ Vehicle Configuration Matrix
CORROSION INDEX
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⬡ READY — CONNECT YOUR OBD ADAPTER
BETA
⬡ STORED FAULT CODES
⬡ PENDING CODES
⬡ FREEZE FRAME — CONDITIONS WHEN CODE SET
⬡ LIVE SENSOR DATA
ENGINE RPM
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SPEED km/h
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COOLANT °C
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LOAD %
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THROTTLE %
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BATTERY V
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STFT B1 %
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LTFT B1 %
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MAF g/s
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⬡ READINESS MONITORS — EMISSIONS / INSPECTION
Feeds codes · freeze frame · sensor readings · monitors into the AI engine
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A few quick questions
TO IMPROVE DIAGNOSTIC ACCURACY
Cross-referencing TSB database...
0%
AUTHENTICATING VEHICLE PROFILE...
ANALYZING FAULT SIGNATURE MATRIX...
CROSS-REFERENCING FAILURE PATTERNS...
MODELING REPAIR PROBABILITY TREE...
COMPILING TARGETED REPAIR PLAN...
⚠ CONNECTION FAULT DETECTED
⬡ Technical Briefing
⬡ Most Probable Fixes
TAP ANY CARD BELOW FOR STEP-BY-STEP REPAIR INSTRUCTIONS
⬡ RETRIEVING REPAIR PROCEDURE...
⬡ Corrosion Labor Factor
⬡ No-Scanner Code Retrieval
⬡ Diagnostic Flowchart
⬡ Targeted Solutions & Components
⬡ Recommended Resources
⬡ SEARCHING FORUMS & MANUALS...
No results found for this vehicle configuration.
⚠ Active NHTSA Safety Recalls
⬡ NHTSA Owner Complaints
⬡ Maintenance Due at This Mileage
GENERATING MAINTENANCE SCHEDULE...
⬡ Supplemental Analysis
Input additional findings, test results, or updated symptoms for a targeted second-pass analysis.
⬡ Refined Diagnosis
⬡ Was this diagnosis helpful?
Rate the quality of your results
Any additional feedback? (optional)
0 / 500
✓ THANK YOU — YOUR FEEDBACK HELPS IMPROVE THE TOOL
⬡ Why OBDecode
TSB + Pattern Failure Cross-Reference
Not a code dictionary. Every diagnosis is run against Technical Service Bulletins and real-world pattern failures for your exact year, make, model, and engine configuration.
Diagnostic Flowcharts
Step-by-step visual decision trees tailored to your fault codes and symptoms. Follow the exact test sequence a technician would run — from initial check to confirmed repair.
Live OBD Scanner Built In
Real-time sensor data via Bluetooth ELM327. Monitor RPM, speed, coolant temp, fuel trims, O2 sensors, and 40+ live PIDs — with per-module ECU reads and Mode 06 monitor tests.
Free During Development. No Account. No App.
Works in any browser. No download, no login, no subscription required. OBDecode is a one-person project, still actively being built — that's the real reason it's free right now, not a permanent promise. The diagnostic engine will keep working the same way once a paid Pro tier arrives for the extras.
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Built by Ian Littlefield
Independent Developer · Automotive Enthusiast
"I built OBDecode because I was tired of paying shops $150 just to tell me what my scanner already knew. It's a one-person project, still being actively built — that's the honest reason it's free right now, not a permanent guarantee. Every feature came from real diagnostic frustration, and the core diagnostic engine will keep working the same way once a Pro tier arrives for the extras."
Professional OBD2 Diagnostic & AI Research
OBDecode is a professional-grade OBD2 diagnostic platform for technicians, enthusiasts, and everyday drivers — built by one developer and still in active development, free to use right now while it grows. Enter your vehicle details and symptoms for AI-powered diagnosis cross-referenced against TSB databases, NHTSA records, real-world pattern failures, and community-submitted fixes — or connect your ELM327 Bluetooth adapter for live sensor monitoring, per-module ECU reads, and guided data logging.
TSB Cross-Reference
Every diagnosis is cross-referenced against Technical Service Bulletins and manufacturer pattern failure records for your specific vehicle configuration and platform. Not guesses — documented failures.
Diagnostic Flowcharts
Step-by-step visual decision trees tailored to your fault codes and symptoms — from the first test to confirmed repair. Follow the same diagnostic sequence a master tech would run.
Component Priority List
Ranked list of components to inspect and test, ordered by diagnostic priority for your specific vehicle platform and reported symptoms. Know what to check first — and what to skip.
No-Scanner Code Retrieval
Retrieve DTCs on supported vehicles without an OBD2 scanner — including Chrysler key dance, GM ALDL blink codes, and Ford self-test procedures. Diagnose from the driver's seat.
NHTSA Recall & Complaint Lookup
Every diagnosis checks active federal safety recalls and owner complaint patterns from the NHTSA database for your exact vehicle. Know if your issue is already documented at the federal level.
Live OBD2 Scanner
Connect your ELM327 Bluetooth adapter for real-time sensor monitoring, live PIDs, and a dedicated ECU Select screen — pick PCM, TCM, ABS, BCM, or any other detected module individually to read data identifiers (DIDs), sweep for hidden DTCs, and run Mode 06 monitor tests on that module specifically. Freeze frame data, monitor readiness status, and clear codes directly from the browser. Module access is read-only: OBDecode does not write to, program, or command vehicle control modules.
Supports all makes including Ford, Chevrolet, Dodge, Toyota, Honda, Jeep, Nissan, Subaru, BMW, Audi, and more. Works with OBD1 and OBD2 vehicles from 1980 to present. No account required. The full diagnostic engine, live OBD2 scanning, data logging, and the full PDF report export are all free and available right now, while the project is in active development — a Pro tier with multi-vehicle garage history and expert consultations is planned as it matures.
Now live: a per-ECU select screen — tap SCAN MODULES to detect every module on your vehicle, then tap one to drill into its own DID reads, DTC sweep, and Mode 06 monitor tests, the same module-first workflow shop scan tools use. Ford and GM/Buick vehicles get corrected manufacturer-specific module addresses automatically. Every module interaction is read-only.
Roadmap: OBDecode is actively developed, and features such as additional manufacturer-specific data reads, guided component testing, and multi-channel sensor graphing are being explored. Roadmap items are plans, not commitments — they may change or never ship, and nothing described as planned should be relied on as a current capability. Always confirm a diagnosis with a qualified technician before performing repairs.
Connect your ELM327 BLE adapter, then tap SCAN. The engine reads stored DTCs, pending codes, freeze frame data, and readiness monitors — all in one pass. Tap DEEP AI DIAGNOSIS to send everything to the AI engine.
⬡ PER-MODULE ECU READS AVAILABLE — TAP TO SELECT AN ECU
VIN DECODED
Pair your ELM327 BLE adapter · Any OBD-II port (2001+) · Web Bluetooth required
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STORED DTC
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PENDING DTC
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MON FAIL
VEHICLE HEALTH SCORE—
BATTERY VOLTAGE—
⬡ AI DEEP DIAGNOSIS
Send all scan data to OBDecode AI engine for repair flowchart, TSB lookup, and root-cause analysis with part numbers
⬡ AI MONITORING PLAN — LOG THESE PARAMETERS
OBDecode identified these as key parameters to capture during your next drive cycle:
Highlighted in gold on LIVE tab. Relevant PIDs auto-selected.
⬡
LIVE DATA TAB
Real-time sensor readings from the ECU — RPM, coolant temp, throttle, MAF, fuel trims, and more. Switch between GAUGES (dial tiles), LIST (all PIDs, tap to pin to gauges), and GRAPH (time-series plot). Select PIDs in LIST view before recording with the data logger in TOOLS.
CONNECT TO START LIVE DATA
SELECT PIDs IN LIST VIEW · TAP GAUGE TO REMOVE
obdecode live --list · tap a row to pin it to the gauges view
0 SELECTED
IDLE
SELECT PIDs IN LIST TAB · THEN TAP REC
— NO DATA —
⬡ SESSION STATS
LOGS ACTIVE PIDs WITH TIMESTAMPS · EXPORT CSV FOR TUNING / DYNO ANALYSIS
⬡
FAULT CODES TAB
Stored codes (Mode 03) are confirmed faults that turned on the MIL. Pending codes (Mode 07) are maturing — seen once but not confirmed. Permanent codes (Mode 0A, 2010+ vehicles) are emission faults the ECU refuses to let you clear — they only go away after its monitors re-run clean. Tap a DTC to get its definition. Use AI DIAGNOSIS → to send all codes to the deep research engine. Clear codes only after diagnosis and repair.
⚠ SHOWING A PREVIOUS SCAN — NOT LIVE. Tap SCAN to read the currently connected vehicle.
obdecode codes --stored --pending · tap a code for AI diagnosis
⬡ STORED FAULT CODES
NO SCAN DATA — CONNECT AND SCAN
⬡ PENDING CODES
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⬡ PERMANENT CODES (MODE 0A)
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⚠ Permanent codes CANNOT be cleared with CLEAR CODES or by disconnecting the battery. The ECU erases them by itself only after its own monitors re-run and pass. A vehicle with a permanent code will fail an emissions test even if stored and pending codes are empty.
⬡ DTC CODE LOOKUP
⬡
FREEZE FRAME TAB
The ECU captures a snapshot of sensor values at the exact moment a fault code is set. This freeze frame is your most important clue — it shows what RPM, load, coolant temp, and throttle position were when the fault occurred. Cross-reference with your DTC for accurate root cause analysis.
obdecode freeze --at-trigger · sensor snapshot from the moment the code set
⬡ FREEZE FRAME — CONDITIONS WHEN CODE SET
FREEZE FRAME CAPTURED WHEN CODES ARE READ
⬡
READINESS TAB
Readiness monitors show whether the ECU has run each emissions self-test since the last code clear. All monitors must show COMPLETE to pass a smog/emissions inspection. After clearing codes, complete a full drive cycle to reset them — typically highway and city driving at varied speeds.
⬡ READINESS MONITORS — EMISSIONS / INSPECTION STATUS
✓ COMPLETE = monitor has run and passed
✗ INCOMPLETE = monitor has not run since last code clear
All monitors must be complete to pass emissions inspection.
READINESS DATA LOADED AFTER FULL SCAN
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ADVANCED TAB
Raw OBD terminal, mode commands, debug log export, and the sensor data recorder — for power users and technicians who want direct ECU access.
⬡ OBD TERMINAL
⬡ OBD MODE COMMANDS
Send raw OBD-II mode commands to the ECU. Mode 01 = live sensor data, 02 = freeze frame PIDs, 03 = stored DTCs, 04 = clear codes, 05 = O2 sensor test results (non-CAN), 07 = pending DTCs, 09 = vehicle info (VIN, calibration IDs), 0A = permanent/emission-related DTCs. Results appear in the debug log.
⬡ DEBUG LOG
Logs every raw ELM327 command and response. Enable before reproducing a connection problem, then DOWNLOAD .TXT and share the log file when reporting adapter issues. The log shows exactly what the ECU said — including any error frames (UNABLE TO CONNECT, NO DATA, BUS BUSY) that indicate communication problems.
ENABLE DEBUG LOGGING
LOGS ALL RAW ELM327 TRAFFIC & PARSED VALUES
⬡ DATA LOGGER
Records timestamped PID values to CSV for ECU tuning and performance analysis. First go to LIVE → LIST tab and check the PIDs you want to record. Then return here and tap REC ●. Tap STOP when done, then DOWNLOAD CSV. Open the CSV in Excel or TunerPro for analysis.
SENSOR RECORDING
IDLE — CONNECT TO START
LOGS ACTIVE LIVE PIDS AS TIMESTAMPED CSV · SELECT PIDS IN LIVE→LIST TAB BEFORE RECORDING · FOR ECU TUNING & DYNO ANALYSIS
obdecode ecu --list · select a control module to address it directly
⬡ SELECT MODULE
Sends requests directly to the selected ECU to read data identifiers (DIDs), sweep for hidden DTCs, and run Mode 06 monitor tests. Module access is read-only in this release — write operations are not offered. These are professional-level tools; do not power off the vehicle mid-session.
⚠ ADVANCED — SENDS COMMANDS TO ECU. WRONG SETTINGS CAN DISABLE SAFETY SYSTEMS.
ALWAYS BACKUP ORIGINAL VALUE BEFORE WRITING. DO NOT POWER OFF DURING WRITE.
WHAT CAN THIS DONGLE + THIS CAR ACTUALLY DO? · READ-ONLY
⬡ ADAPTER + VEHICLE CAPABILITY REPORT
TAP SCAN MODULES TO DETECT ECUs ON THIS VEHICLE
NO SESSION
CONNECT ADAPTER THEN ENTER SESSION
TAP TO ACTIVATE · TAP AGAIN TO STOP · MAKE-SPECIFIC COMMANDS LOADED FROM VEHICLE INFO
FACTORY-PROGRAMMED ECU SEQUENCES — RUNS FULL ROUTINE THEN READS RESULT
QUICK READ
READ CURRENT VALUE FIRST — ORIGINAL IS BACKED UP AUTOMATICALLY BEFORE ANY WRITE
SCANS EVERY KNOWN MODULE FOR STORED DTCs · UDS SERVICE 0x19 02 08 (BY STATUS MASK) · OBD MODE 03 FOR FALLBACK
ON-BOARD MONITOR TEST RESULTS · RAW VALUE vs PASS/FAIL THRESHOLD · CATALYST · O2 · EVAP · MISFIRE · EGR · SECONDARY AIR
SECURITY ACCESS GATES DEALER-LEVEL FUNCTIONS · KEY ALGORITHM IS MANUFACTURER-SPECIFIC · MANY OLDER VW/GM ARE PUBLIC
⬡ J1850 PWM DETECTED — UDS NOT AVAILABLE ON PRE-CAN VEHICLES.
USE EEC SELF-TESTS BELOW. STANDARD OBD-II (DTCs, LIVE DATA) WORKS NORMALLY.
FORD EEC SELF-TEST (MODE 08)
SCP MODULE SCAN (J1850 PWM)
⬡ GUIDED DIAGNOSIS
Walks you through a specific symptom one step at a time, using the same module scan and fault-code read the manual tools use. Everything it does is read-only — it never writes, clears, codes or bypasses anything. Simple enough to follow without a car-electronics background.
OBD OFFLINE
0–60 MPH
0.00
IDLE — TAP ARM TO PREPARE
0
MPH · SENSOR
iOS 13+ requires explicit permission for accelerometer
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TIME
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PEAK G
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TOP SPEED
⬡ OBD SPEED USED AUTOMATICALLY IF SCANNER TAB IS OPEN
⬡ DEVICE ACCELEROMETER USED AS FALLBACK — MOUNT PHONE FLAT
⬡ LAUNCH DETECT: LONG-G > 0.15 OR SPEED > 3 MPH
⬡ MOUNT IN LANDSCAPE ON DASH · SCREEN FACING DRIVER
0.00
LONG G
0.00
LAT G
0.00
COMBINED
0.00g
PEAK ACCEL
0.00g
PEAK BRAKE
0.00g
PEAK LAT
MOUNT PHONE FLAT ON DASH · SCREEN UP · CALIBRATE ZERO BEFORE DRIVING
RING = 1G · OUTER EDGE = 1.5G · DOT = CURRENT VECTOR · TRACE = LAST 3s
VEHICLE WEIGHT
CURB WEIGHT + FUEL + DRIVER. CURB WEIGHT IS USUALLY 10–15% UNDER TOTAL.
ARMS TIMER AUTOMATICALLY · ACCELERATE HARD FROM STANDSTILL TO TOP SPEED OR REV LIMIT
ESTIMATED WHEEL HORSEPOWER
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WHEEL HP (ESTIMATED)
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LB-FT TORQUE
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SPEED @ PEAK HP
⚠ WHEEL HP ESTIMATE ±15–25% · EXCLUDES DRIVETRAIN EFFICIENCY VARIATION, AIR DENSITY,
ALTITUDE, AND SURFACE CONDITIONS. FOR REFERENCE AND TREND TRACKING ONLY — NOT A DYNO.
⬡ VEHICLE INFORMATION
VIN—
YEAR—
MAKE—
MODEL—
ENGINE—
OBD PROTOCOL—
ADAPTER—
CALIBRATION ID—
CVN—
ECU NAME—
LAST SCAN—
⬡ SCAN HISTORY
NO HISTORY YET
⬡ PERFORMANCE RUNS
NO RUNS RECORDED YET
⬡ HUD MODE
HEADS-UP DISPLAY
MIRROR DISPLAY FOR WINDSHIELD REFLECTION
⬡ DISPLAY
THEME
THEME
ACCENT COLOR
FONT
BACKGROUND
FONT SIZE
UI SCALE
DENSITY
REDUCED MOTION
HIGH CONTRAST MODE
⬡ SHOP BRANDING SHOP TIER
SHOP NAME
PREVIEW
OBDecode
⬡ SETTINGS
Units, poll rate, and connection behavior. FAST poll (200ms) gives the smoothest live data but consumes more BLE bandwidth — use NORM or SLOW on older adapters that can't keep up. Wake Lock prevents the screen from sleeping while connected, useful when monitoring during a test drive.