ELM327 Mini Manual: Bluetooth PIN 1234, Pairing Order and Overnight Drain

Unbranded clones sometimes use a different default. If 1234 is refused, try the other two common codes before blaming the dongle.

1. 1234: the default on most blue and black minis.
2. 0000: used by some older Bluetooth modules.
3. 6789: found on a smaller group of clones.

The PIN number for ELM327 mini dongles is fixed in the Bluetooth module rather than chosen by you, so there is nothing to reset if you forget it. It also offers little protection: anyone who knows the default can pair while the mini has power. That is one more reason to pull it out when the car is parked on a busy street.

Bluetooth LE and Bluetooth 5.1 minis skip the PIN. The Panlong PL-B04 and the ViaBecs connect from inside the app with no code screen. The Wi-Fi mini's hotspot has no password either, a detail its maker states outright.

Where the password is a field rather than a prompt, as on some Android head units, type 1234 into it before starting the search. JOYING lists the password in the spec line of its head-unit mini, right next to its 5–10m range.

How to pair ELM327 mini dongles on Android

1. Find the port under the dash, usually below the steering column, and press the mini in until it seats.
2. Turn the ignition to ON; the mini's light should come on.
3. On Android, open Settings › Bluetooth › Pair new device.
4. Choose OBDII, OBD2 or ELM327 from the list and enter 1234.
5. In the app, pick Bluetooth as the link, then the same device name.
6. Start the engine, or leave the ignition on, and tap Connect.

Panlong adds a useful exception. If OBDII does not show in the phone's list, run the app anyway, since it can find the mini on its own. Car Scanner can start pairing from its adapter settings for the same reason.

Android 12 and newer ask each app for Nearby devices permission. Refuse it and the app sees no Bluetooth at all. Veepeak's notes for Android 13 go a step further: set both Bluetooth and Bluetooth Legacy to unrestricted battery use, or the system may cut the link.

• No light on the mini: suspect the accessory-socket fuse first, as Veepeak advises.
• Light on, no Bluetooth name: unplug the mini, restart the phone's Bluetooth, plug back in.
• Paired but no data: push the mini harder into the port, since power alone does not prove a good contact.

1. Read the stored codes and note every one, pending codes included.
2. Open the freeze frame for each code: the speed, load and temperature when it set.
3. Check I/M readiness to see which monitors have completed.
4. Watch live data with the engine warm: coolant temperature, fuel trims, O2 sensors.
5. Fix the cause, then clear the codes, which switches the lamp off.

Clearing first wipes the freeze frame and resets the readiness monitors. A car taken for an emissions test soon after a clear can fail on incomplete monitors, even with nothing wrong.

The mini reads the engine and emissions side through standard OBD-II. Veepeak spells out what stays out of reach: ABS, airbags, TPMS, transmission, HVAC and service resets. Those need a brand-level tool, not a different app on the same dongle.

• Generic P0 codes show up on every car with an OBD-II port.
• Manufacturer P1 codes depend on the app's code database.
• Hybrid battery data needs Dr. Prius or a similar app on a Toyota or Lexus.

Which app suits each of these steps depends on your phone. The app setup notes compare Car Scanner, Torque Lite and OBD Fusion on the mini, menu by menu.

Mount the phone rather than holding it when live data runs on the road. A second person reading the screen is better still.

JOYING gives a working current of 45mA for its mini, one of the few figures any mini maker prints. At that rate a 60Ah battery loses half its charge in about four weeks, and the car's own standby draw shortens that further. Cold weather, an older battery or short daily trips cut the margin again.

• Daily driver, healthy battery: overnight is usually no problem.
• Car left for seven days or longer: pull it.
• Old battery or deep winter: unplug it every time.
• Light still on long after locking up: treat that unit as a non-sleeper.

Some minis power down on their own. The Wi-Fi mini's maker says it sleeps after half an hour without communication and calls it plug-and-leave. The genuine ELM327 chip has a low-power mode, but clone boards do not always make the Bluetooth module follow it, so a sleeping chip can sit beside an awake radio.

A mini hanging from the port can catch a knee as well. The short shells sit close to the dash, but check that yours clears your leg and the pedals before driving with it plugged in.

The Veepeak VP11 and the other Classic minis give no sleep figure at all. Without one, the safe habit is to unplug.

The blue v2.1 mini comes in two-packs for this reason, one dongle living in each car. With two paired devices sharing a name, apps like Torque may connect to whichever the phone lists first.

1. In the phone's Bluetooth menu, forget the dongle from the other car.
2. Pair the one in this car with its PIN.
3. Reselect it in the app's adapter settings.

YMOBD sidesteps the chore on the Bluetooth LE minis: Panlong says it manages and switches between several scanners. The Wi-Fi mini needs its own routine, as its maker describes it: disconnect the Wi-Fi and close the app after one car, then rejoin the network once the dongle sits in the next.

• Mark each mini with a paint pen so you know which car it lives in.
• Keep one app profile per car where the app supports it.
• Pull the mini before a long stay in an airport car park.

A two-pack also covers a failed unit. Clones do die, usually from a knock or a cracked shell, and a spare in the glovebox keeps the phone setup unchanged: same PIN, same name, same app.

For iPhone owners, the iPhone setup notes explain which minis connect with no pairing at all.