OBD-II adapters that work with an iPhone, tested on a real car

Which OBD-II adapters work with an iPhone?

Bluetooth Low Energy ones, plus the one classic Bluetooth adapter Apple's MFi program lets WrenchTime use, the OBDLink MX+. An iPhone app can reach a classic Bluetooth adapter only when the adapter's maker has certified it for that app by name, so any other adapter that pairs from iPhone Settings is on a radio this app cannot use, and a Wi-Fi adapter joins its own network rather than answering an app: a listing that says Android or Wi-Fi is not the one to buy. WrenchTime speaks the ELM327 command set and keeps a running log of what specific adapters actually did, rather than claiming a compatibility list it has not tested.

• Vgate iCar Pro and iCar Pro 2S confirmed working on a real vehicle. Found by the scan, connect and poll, and wake on their own when the app connects, so a trip that starts with the adapter asleep still gets a session.
• OBDLink MX+ Apple-certified (MFi) and confirmed working, supported since WrenchTime 6.7. Pair it once in iPhone Settings > Bluetooth, then link it to a vehicle in Settings > Connections like any other adapter.
• Vgate iCar, the non-Pro works, but does not wake by itself: press its button before the drive or the scan comes up empty.
• Vgate vLinker MS ships in Apple MFi mode, and its certification does not name this app, so it must be switched to BLE with Vgate's own updater app and then forgotten in iOS Bluetooth settings.
• Anything else if it is BLE and speaks ELM327 it should work, and the app measures your particular adapter rather than assuming. Tell us what you saw and it goes in the log.

Why does a Wi-Fi or classic Bluetooth adapter not show up?

Because WrenchTime cannot reach it. iOS lets any app talk to a Bluetooth Low Energy device directly, which is why a BLE adapter is found by the scan inside the app and never paired in iPhone Settings. A classic Bluetooth adapter is different: iOS hands it to an app only when the adapter is MFi-certified for that app by name, which today is true of the OBDLink MX+ alone. A Wi-Fi adapter makes a network of its own for the phone to join, and WrenchTime does not read adapters over Wi-Fi. So it is the radio that decides, not the car: look for Bluetooth Low Energy, BLE or Bluetooth 4.0 on the listing, and be wary of one sold for Android only, which usually means classic Bluetooth.

How is the OBDLink MX+ set up differently?

It is paired once in iPhone Settings > Bluetooth, like a pair of headphones, because it is a classic Bluetooth accessory certified by Apple. After that you link it to a vehicle inside WrenchTime exactly like a BLE adapter, and the app talks to it through Apple's accessory framework rather than through its own Bluetooth scan. A BLE adapter is the opposite: it is never paired in iPhone Settings, only found by the scan inside the app. A BLE adapter paired in iPhone Settings anyway, or a vLinker MS still in MFi mode, is the usual reason the scan comes up empty.

Does the adapter wake up on its own?

Most do, and it matters: a trip that starts while the adapter is asleep records no engine data. The Vgate iCar Pro and iCar Pro 2S come out of sleep by themselves when the app connects, so a drive that begins with the adapter asleep still gets its readings. Two exceptions are on record. The non-Pro Vgate iCar never wakes by itself and has to be switched on with its button before each drive. And the iCar Pro line does not wake on a BMW, which is what Vgate sells the vLinker BM+ for; that one is confirmed working too.

How do I link an adapter to a vehicle?

Plug the adapter into the car's OBD-II port, usually under the dashboard on the driver's side, turn the ignition on, and open Settings > Connections in WrenchTime. Pick the vehicle, switch to its OBD-II tab and let the scan run: the adapters it recognizes are listed first, and a tap links one to that vehicle. The first connection runs a Connection Check that watches speed and revs for a few seconds and shows how fast your link answered. From then on, with Connect During Trips switched on, every trip recorded in that vehicle opens a session by itself and closes it when the trip ends, and the readings are kept with the trip.

Why does my car alarm go off with the adapter plugged in?

Some modern cars read traffic on the diagnostic port of a locked car as a break-in, and most adapters stay powered and connected long after the engine is off. Each vehicle has a switch for this in its adapter pairing screen, off by default, that only applies when no one is at the screen: a trip, CarPlay or the Live dashboard.

• Disconnect When the Vehicle Sleeps the app stops talking to the car the moment the engine reads zero revs, the car's own Bluetooth drops or the bus goes quiet, and picks up on the same link once the car moves again, without reconnecting. Start-stop pauses the readings too, until you drive off.
• Also Drop the Bluetooth Link for a car whose alarm objects to the idle link itself: the session ends on the same signals and reconnects when the drive resumes, which costs a few seconds of readings at every drive-off.

What if the pairing scan does not recognize my adapter?

The scan lists the adapters it recognizes first, and below them the other named Bluetooth devices nearby with a usable signal. Pick one of those and WrenchTime tries it on the spot: it is kept only if it answers like an OBD-II adapter, and otherwise the screen says so and your previous link is left as it was. Other people's devices are never named in the diagnostic log. If an unlisted adapter works for you, tell us and it goes in the adapter log above.