If you have an iPhone and a check engine light on, a small OBDII adapter can read the code on the phone.
The car’s computer watches the engine and transmission. When it sees a problem it turns the light on and stores a trouble code.
Every car and light truck sold in the US since 1996 has an OBDII port. That is the 16-pin plug under the dash that a scan tool hooks up to.
A handheld scanner still works. In 2026 an iPhone does too, as long as the adapter is made for iOS. Cheap generic Bluetooth ELM327 dongles are usually Android-only and will not pair right with an iPhone.
Where is the OBDII Port?
On most vehicles the OBDII port is on the driver side under the dashboard, near the steering column. Look up around the knee panel. Some trucks hide it behind a small cover.
Plug the adapter in with the key on, or the engine running. The adapter gets power from the port.
What OBDII Adapter Works With an iPhone?
iPhone needs Bluetooth Low Energy (BLE), or an Apple MFi adapter. Classic Bluetooth serial dongles that Android likes will not work.
WiFi ELM327 adapters used to be the iPhone workaround. They still function, but the phone has to join the dongle’s WiFi and you lose regular internet while it is connected. BLE is the better option now.
Connect from inside the app. Do not pair the adapter in iPhone Settings, Bluetooth. That is where a lot of people get a “not supported” error.
A basic BLE dongle reads generic engine codes, freeze frame, and live data. It will not do ABS, airbag, or transmission codes. For that you want BlueDriver or OBDLink MX+.
- BlueDriver Bluetooth Pro – easiest iPhone pick. Own app, no subscription, reads check engine plus ABS / SRS / TPMS on a lot of 1996 and newer gas cars.
- Veepeak OBDCheck BLE – low-cost BLE dongle. Needs a third-party app such as OBD Fusion or Car Scanner ELM OBD2. Good for engine codes, not ABS or airbags.
- OBDLink MX+ – more serious adapter. Works with the OBDLink app and others like Carista and BimmerCode. Faster live data, and extra OEM coverage on Ford, GM, Toyota, Honda, and similar.
How Do You Read the Code on an iPhone?
Plug the adapter into the OBDII port. Turn the key on.
Open the app that matches the adapter. Let it connect, then read codes. Write the code down, like P0420 or P0301, before you clear anything.
Look the code up, or watch a how-to for that exact code and vehicle. That is the same idea as using a laptop as an OBDII scanner, just on the phone.
Clearing the light without a repair just turns it back on. Use clear after the fix, or to see if a pending code returns.
FIXD and a few other “plain English” apps still exist. A lot of them want a yearly subscription after the dongle is bought. BlueDriver does not.
These adapters will not start the car, track where you have been, or replace a shop scan tool for programming. They will tell you why the light is on, and that is enough to decide if it is a DIY job or a shop job.
Have you used an iPhone to pull a check engine code? Let us know what adapter worked below.