Diagnostics · 6 min read

OBD2 on iPhone: Live Engine Data and Fault Codes Inside TorqueTrail

A check-engine light tells you something is wrong, not what. Plug a small OBD2 adapter into your car and TorqueTrail shows you the fault codes behind it, along with live engine data, right next to the rest of your garage.

Published

Key takeaways

  • TorqueTrail works with any ELM327-compatible OBD2 adapter. On iPhone it connects over Bluetooth LE or Wi-Fi; the adapter is sold separately.
  • Once connected you see live engine RPM, vehicle speed, coolant temperature and fuel level, updating on screen.
  • You can read both stored and pending fault codes, and clear them once the problem has been fixed.
  • Clearing a code turns the check-engine light off. It does not repair the fault, and the code can come back if the problem is still there.
  • OBD2 is live on iPhone today. Android is coming soon, with Bluetooth LE, Bluetooth Classic and Wi-Fi adapters.

The light that doesn't explain itself

Every modern car has an OBD2 port, usually under the dashboard near the steering column. It's the same port a workshop plugs into when your check-engine light comes on, and it's where your car reports what its sensors are seeing and which faults it has logged.

The light on your dashboard only says that something was logged. The code behind it says what. Without a way to read that code, you're left choosing between ignoring the light and booking a visit just to find out what it means.

TorqueTrail's OBD2 Diagnostics closes that gap. With a small adapter in the port, the app reads the same codes and live data, on your phone, alongside the vehicle it belongs to in your garage.

What you need

One ELM327-compatible OBD2 adapter. ELM327 is the command set most consumer adapters speak, so you aren't locked to a particular brand. The adapter is sold separately.

On iPhone, pick one that connects over Bluetooth LE or Wi-Fi. Adapters that only use Bluetooth Classic aren't supported on iPhone.

  • iPhone: Bluetooth LE and Wi-Fi adapters, live now
  • Android: Bluetooth LE, Bluetooth Classic and Wi-Fi adapters, coming soon

Live engine data

Once you're connected, TorqueTrail reads four values from the adapter and keeps them updating on screen:

  • Engine RPM
  • Vehicle speed in km/h
  • Coolant temperature in °C
  • Fuel level as a percentage

Honest blanks

Not every car reports every value. If yours doesn't report one, TorqueTrail shows it as blank rather than filling in a guess. A missing number is more useful than a made-up one when you're trying to work out what's going on.

Stored and pending fault codes

Cars keep two kinds of fault codes, and TorqueTrail shows both. Stored codes are faults the car has confirmed, usually the ones behind a lit check-engine light. Pending codes are faults the car has noticed but not yet confirmed. They're an early hint, and they can turn up before the light ever comes on.

Seeing both gives you something concrete to look up, or to hand to your mechanic, instead of just "the light is on."

Clearing codes, and what clearing doesn't do

When a repair is done, you can clear the codes from the app, and the check-engine light goes off.

Clearing isn't a fix, though. It wipes the record and turns off the light; it doesn't touch whatever caused the fault. If the underlying problem is still there, the car will log the code again and the light will come back. Clear codes after the fault has been fixed, not instead of fixing it.

Your data stays between you and your adapter

TorqueTrail only talks to the adapter you choose so it can show you your engine data. Nothing is shared.

Where to find it

Plug the adapter into your car's OBD2 port and turn the ignition on. In TorqueTrail, open a vehicle in your garage and tap OBD2 Diagnostics.

Bluetooth LE adapters show up in an in-app list; for a Wi-Fi adapter, type in its address. Next time, reconnect to your last adapter in one tap.

For the full rundown and FAQ, see torquetrail.online/obd2-scanner.