The short answer
Look for the OBD2 port under the steering wheel, around the driver's knees. Plug in the tool's cable with the car switched off, turn the ignition on without starting the engine and let the tool read the chassis number (VIN). Within two or three minutes the car is identified and you can start the scan.
It is the first thing everyone does when they open the box, and yet it is where most questions come up. The tool won't switch on, you can't find the port, or it sits on "communicating" and goes no further. It can almost always be sorted in a minute. Here is how to get it right from the start.
What OBD2 is
OBD2 (or EOBD, the European version) is the self-diagnosis system cars have had for more than twenty years. The car monitors its own emissions and engine running and, when something goes wrong, stores a fault code and turns on the engine warning light. The OBD2 port is the socket a diagnostic tool uses to read those codes.
OBD2 codes are the same on every make: a P0420 means the same on a SEAT as on a Toyota. That is what any cheap OBD2 scanner reads. But OBD2 only covers the engine and emissions. The ABS, airbag, gearbox, central locking or electronic parking brake talk through the same socket using each manufacturer's own protocols, and to get into those you need a diagnostic tool that knows the make, such as an iCarsoft.
Where the OBD2 port is
Every petrol car sold in Europe since 2001 and every diesel since 2004 has a 16-pin OBD2 port. The standard requires it to be inside the cabin, within the driver's reach. In practice you will find it in one of these places:
| Location | Where to look | Where it usually is |
|---|---|---|
| Under the steering wheel | To the left of the steering column, at knee height. Sometimes facing downwards. | Most cars: VW, SEAT, Skoda, Audi, Ford, Toyota |
| Behind a cover | A small flap in the lower dashboard trim, near the pedals or the bonnet release lever. | BMW, Mercedes, Renault, Peugeot, Citroën |
| Next to the fuse box | Behind the side panel of the dashboard or the cover of the interior fuse box. | Some Opel/Vauxhall, Fiat and Hyundai models |
| Centre console | In front of the gear lever, or under an ashtray or storage tray. | Some Fiat, Alfa Romeo and older models |
If you can't find it, check the fuses or diagnostics section of the car's handbook. The connector is trapezoid-shaped with 16 pins in two rows. You can't miss it.
Step by step: connecting the tool
- Switch the car off and take the key out, or leave the start button in the off position.
- Plug the tool's OBD2 cable into the port. It only goes in one way: don't force it. On handheld tools (such as the CR Pro or the V2.0 single-brand tools) the port itself powers the unit and it switches on by itself.
- Turn the ignition on without starting. In other words, all the dash lights on but the engine off. On cars with a start button, press it without touching the brake or clutch.
- Choose the make or let it read the VIN. Almost every current iCarsoft reads the chassis number and recognises the make, model, year and engine. If it asks you to choose by hand, take your time: picking the wrong engine is the number one reason it "can't find" a control unit.
- Run the auto scan. The tool goes through every control unit and tells you which ones have faults. From here you can read, clear or carry out whatever servicing you need.
Engine running or off?
For reading and clearing faults and for most servicing jobs, ignition on and engine off. There are exceptions, and the tool itself will tell you: engine live data makes more sense with it running, as do particulate filter regeneration and some steering calibrations. If you do start the engine, make sure you are somewhere well ventilated and never in an enclosed garage.
Battery. With the ignition on and the engine off, the car drains the battery. For a quick read that is no problem, but if you will be at it for more than 15 or 20 minutes (coding, several functions in a row), connect a charger or battery support unit. Low voltage causes communication errors and false faults.
If the tool won't switch on or won't communicate
Check these in order. Nine times out of ten, the answer is here:
- It won't switch on. Pin 16 on the port supplies the 12 V. On many cars it shares a fuse with the cigarette lighter or the 12 V socket. If the lighter doesn't work, you know where to start.
- It switches on but won't connect. Check that the ignition is on. With the car completely off, many control units don't respond.
- Wrong car selected. Go back and let it read the VIN, or check the year and engine.
- Bent or dirty pins in the car's port. It happens a lot on cars where someone has left a tracker or dongle plugged in.
- Accessories plugged in. Unplug GPS trackers, insurance black boxes or Bluetooth readers that share the port.
- Cars with a security gateway. Some recent Fiat, Jeep, Alfa Romeo and other Stellantis models let you read but not clear faults without unlocking it. We explain it in the FCA security gateway.
- Out-of-date software. If your car is very new, update the tool. We show you how in how to update an iCarsoft.
Cable, Bluetooth or VCI: what changes
Handheld tools always use a cable. Tablets such as the CR Max P or the CR Ultra use a small module (VCI) that plugs into the port and talks to the tablet over Bluetooth. The connection is the same; you can just walk around the car with the screen in your hand. Handy for component tests or for watching live data with the bonnet up.
What next
With the tool connected, you would normally start with a full scan and read the faults. If you are after something specific, we have guides for the oil service reset, the electronic parking brake and the particulate filter. If you don't have a tool yet, start with diagnostic tools for DIY drivers.
