Tesla diagnostic software: Scan My Tesla, OBD adapter & what it shows (2026)
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Drivetrain · RWD, AWD, AWD Performance
Updated · June 14, 2026
Quick FAQ
What's the most popular Tesla diagnostic software?
**Scan My Tesla** (iOS/Android, ~$10) is the community de-facto standard. It connects to the car through an OBD adapter over Bluetooth/Wi-Fi and shows what the stock menu doesn't: real battery capacity (Nominal Full Pack), cell imbalance in mV, pack temperatures, charge power and efficiency, current, isolation. Alternatives are TM-Spy and the built-in Service Mode (no hardware, less detail).
Which OBD adapter do I need for Scan My Tesla?
Two parts: **(1)** an adapter to the car's diagnostic port and **(2)** an OBD-II dongle. Model 3/Y use a non-standard port (4-pin behind the trim at the rear of the center console) — you need a dedicated Tesla-to-OBD-II cable. Model S/X access is different. Dongle — Bluetooth/Wi-Fi: proven **OBDLink MX+ / LX** or **Vgate iCar Pro**. Cheap ELM327 clones often can't handle Tesla's data stream.
What should I check in Scan My Tesla when buying a used Tesla?
Three numbers: **Nominal Full Pack** (current usable capacity) vs **Full Pack When New** = real SOH (aim for ≥85%); **cell imbalance** — <30 mV for NMC/NCA, <10 mV for LFP; peak **charge power** on a fast charger. More reliable than the odometer — a rolled-back mileage shows up as a mismatch between SOH and claimed km.
Can I check a Tesla battery without buying an adapter?
Partly, yes. The built-in **Service Mode** (Controls → Software → hold the model name → code 'service' → Battery section) shows the configuration and some data with no hardware. Since 2025.8 Tesla also has its own **battery health test** in the menu. For deep diagnostics (per-cell imbalance, history) you still need Scan My Tesla + adapter, or the paid certified **Aviloo** test.
Scan My Tesla is the go-to Tesla diagnostic app: what Tesla hides from the owner, it reads straight off the car's bus. Real battery state, cell imbalance, temperatures, charge efficiency — everything you need to judge a used car or catch a problem early.
What you need to connect
- The Scan My Tesla app — iOS App Store or Android Google Play, one-time ~$10. Alternative — TM-Spy (similar features).
- An adapter to the diagnostic port:
- Model 3 / Y — non-standard 4-pin port behind the trim at the rear of the center console. You need a dedicated Tesla→OBD-II cable (AliExpress/local, ~$20-40).
- Model S / X — diagnostic access differs (behind the center console / under trim); match the adapter to your year.
- An OBD-II dongle over Bluetooth/Wi-Fi. Working ones: OBDLink MX+ / LX, Vgate iCar Pro. Cheap ELM327 clones often choke on Tesla's data — get a proven one.
Total kit — roughly $40-120 depending on the dongle. Buy once, use forever.
Key readings (and what they mean)
| Scan My Tesla parameter | What it is |
|---|---|
| Nominal Full Pack | Current usable capacity (after degradation and BMS calibration) |
| Full Pack When New | Fixed "from the factory" figure — uniquely identifies the pack |
| SOH (Nominal / When New) | Real battery wear in % |
| Cell imbalance (mV) | Spread of cell voltages — the key problem indicator |
| Brick / Cell temps | Pack temperatures (matters for charging/performance) |
| Charge power / efficiency | Power and efficiency while charging |
How to read it when buying used
The most accurate way to avoid a dead battery or a rolled-back odometer:
- SOH ≥ 85% for mileage up to ~150k km. If SOH is well below the claimed mileage, the odometer is probably rolled back (see the used-buying checklist).
- Cell imbalance: <30 mV for NMC/NCA, <10 mV for LFP (LFP is stricter). Big imbalance on NCA 82 kWh Panasonic is a known issue.
- Compare Nominal Full Pack vs Full Pack When New to identify the pack and its real degradation. Cross-check with the battery chemistry guide.
Alternatives to Scan My Tesla
- Service Mode — built-in, no hardware: the Battery section shows configuration and basic data. Since firmware 2025.8 Tesla also has its own battery health test. Less detail, but free (how to enter — in the certificates & Service Mode article).
- TM-Spy — a Scan My Tesla analog.
- TeslaMate — continuous logging (needs a server/Raspberry Pi), for long history rather than a one-off check.
- Aviloo — a paid certified battery-health test (issues a report/certificate), handy for resale.
Related articles
- Used Tesla buying checklist — where to plug Scan My Tesla in and what to measure
- Battery chemistry guide (NCA, NMC, LFP, 4680) — identify the pack by its numbers
- 82 kWh Panasonic module imbalance — the main thing diagnostics catches
- Module/cell replacement — if diagnostics found a problem
Sources
- https://www.scanmytesla.com/
- tff-forum.dein Germanhttps://tff-forum.de/t/wiki-akkuwiki-model-3-y-s-x-ct/107641
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