Using the application
Car Diagnostics has two clients:
- Mobile app (Android, Cordova) — direct adapter connection, DTC reads, live telemetry.
- Web panel — fleet management, session history, reports, AI agent chat.
How do I read DTC trouble codes?
Reading DTCs is the core feature of Car Diagnostics. Plug an OBD-II adapter into your vehicle’s port, pair it with your phone over Bluetooth, open the app, and tap Scan DTC. The app queries every electronic control module (ECU, TCM, ABS, SRS) and returns both stored and pending codes. For each code, the AI agent provides an explanation in English and suggests likely root causes based on your vehicle’s make, model, and year.
What do the different DTC categories mean?
Trouble codes are grouped by the first letter of the code:
- P (Powertrain) — engine, transmission, fuel system (e.g. P0301 — cylinder 1 misfire).
- B (Body) — body systems: central locking, windows, climate control.
- C (Chassis) — chassis: ABS, stability control, suspension.
- U (Network) — CAN bus communication errors between modules.
Car Diagnostics reads all four categories, but P-codes are the most common since they cover engine and transmission faults.
Can I scan while driving?
Yes, the app supports scanning both while stationary and during a drive. For load-dependent diagnostics (e.g. P0299 — turbocharger underboost), recording data under real driving conditions produces more accurate results. Ensure your phone is securely mounted and your attention stays on the road. All data is logged and available for review in the session history.
What if codes won’t read?
Common causes: the ignition is off (turn to the second position or start the engine), the adapter does not support your vehicle’s CAN protocol, or the OBD-II port is inactive on some European models without the engine running. If the problem persists, try the adapter on another vehicle — this helps isolate whether the fault is with the adapter or the car’s compatibility.
How do I view live telemetry (PID data)?
Live telemetry lets you watch real-time sensor readings at polling rates up to 5 Hz. Navigate to the PIDs screen and select the parameters that interest you from the list of supported Parameter IDs. Each PID corresponds to one sensor or a calculated value from the ECU.
What PIDs are available by default?
The app provides 12 canonical PIDs covering the essential engine parameters:
| PID | Parameter | Unit |
|---|---|---|
| 04 | Calculated engine load | % |
| 05 | Coolant temperature | °C |
| 0B | Intake manifold absolute pressure | kPa |
| 0C | Engine RPM | rpm |
| 0D | Vehicle speed | km/h |
| 0F | Intake air temperature | °C |
| 10 | Mass air flow (MAF) | g/s |
| 11 | Throttle position | % |
| 21 | Distance traveled with MIL on | km |
Charts render on-device with zero network latency. The web panel offers expanded timeline views for previously uploaded sessions.
Can I add custom PIDs?
If your vehicle supports manufacturer-specific PIDs, you can enter their hex codes manually. The app automatically reads the list of supported PIDs on connection, so you can verify a PID is available before trying to use it.
How do I browse session history?
Every diagnostic session is automatically saved to the cloud.
Where do I find the history?
In the mobile app, open the History screen — sessions are listed by date, newest first. You can search by VIN, date range, and session status (active or completed). The web panel shows aggregated analytics across your entire fleet: total sessions, most frequent codes, average scan duration.
Why is session history useful?
Comparing current codes against past data helps track fault recurrence after repairs, detect new codes that appeared over time, and identify patterns in pending-code frequency. For fleet managers, this aggregated view highlights which vehicles need attention before a breakdown occurs.
How do I clear codes after a repair?
Once you have fixed the underlying issue, you can clear stored DTCs (Mode 04) directly from the app. This operation requires explicit confirmation with a warning: clearing codes is an active write to the ECU, and the downstream effect varies by manufacturer. On some vehicles, clearing DTCs also resets oxygen sensor adaptations and idle trims, requiring a warm-up drive cycle for relearning.
Is read-only mode safe?
All read operations (Mode 01, 03, 09) are fully passive and safe — they only request data without writing anything. Car Diagnostics never executes any write commands without your explicit consent.
Do codes clear themselves over time?
Some codes (especially pending ones) may auto-clear after 40–100 warm-up cycles without the fault recurring, depending on the vehicle manufacturer. Stored (confirmed) codes remain in ECU memory until explicitly cleared or the fault is fixed.
How do I use the web panel?
The web panel is available at obdllm.com after signing into your account (email+password or QR-code sign-in from the mobile app).
What features does the web panel offer?
- Fleet management — add multiple vehicles, view their overall health status.
- Session history — filter by VIN, date, DTC code, or session status.
- Reports — generate PDF diagnostic reports for printing or sharing with a mechanic.
- AI chat — text conversation with AI agents for code analysis, failure prediction, and repair recommendations.
- Access control — invite mechanics or managers with role-based permissions.
The web panel lets you review data collected by the mobile app without reconnecting to the vehicle — everything syncs through the cloud automatically.
How do I share data with a mechanic or shop?
Send a PDF session report via email or messenger. If the mechanic also uses Car Diagnostics, you can grant them vehicle-level access through the Invite user function — they receive a Viewer or Technician role with limited permissions.
Golden path: from install to first DTC report
Sample first-session walkthrough — 8 minutes from download to a saved report:
- Install the app from Google Play (link on /en/download/) — takes about 30 seconds on solid WiFi.
- Create an account — email or Google Sign-In. The Free tier activates automatically.
- Add a vehicle by VIN (17 characters) or manually (make/model/year/engine). The VIN decoder auto-fills all fields.
- Pair the adapter — ignition ON, plug the ELM327 into the OBD-II port (usually lower left under the steering column), pair via Bluetooth (step-by-step: /en/docs/adapter-pairing/).
- Tap “Scan” — the app polls all 5 system groups (engine, transmission, ABS, airbags, body). Takes 30-90 seconds.
- Read the result — list of DTC codes. Free tier shows the bare fault code only; paid tiers add the official description and AI diagnosis with likely causes and repair guidance.
- Save the report — a PDF is automatically saved to History and syncs to the web panel.
- (Optional) Enable live monitoring to record PIDs during a drive — useful for diagnosing intermittent problems.
Gestures and shortcuts (mobile app)
- Swipe left on a session — quick delete (with confirmation)
- Long-press on a DTC code — copy to clipboard
- Swipe down on any list — pull-to-refresh / re-scan
- “SOS” button on the bottom bar — direct support contact
Common tasks
| Task | Where | How long |
|---|---|---|
| Read DTCs | Home → “Scan” | 30 s |
| Clear DTCs | History → session → “Clear” | 5 s |
| Live PID monitor | Home → “Live” | instant |
| Export CSV log | History → session → ⋮ → “Export CSV” | 2 s |
| VIN lookup | Profile → vehicle → “Info” | 1 s |
| Cloud backup | Profile → “Backup to Cloud” | 10-30 s |
App screenshots — on /en/demo/.