Vehicle Diagnostics - A Guide

If you’re not familiar with Car Diagnostics the following guide has been prepared to help you understand it a little more.

In modern vehicles, ECUs (Electronic  Control Units) are standard equipment. The ECU is basically a computer which can monitor parts of the vehicle as well as change settings in the vehicle. ECUs also have the ability to record faults in their memory which can be retrieved by anyone using the right diagnostic equipment.

The systems that can be diagnosed depend on the equipment you use.  For instance using a code reader which is specific to Volkswagens will not work on a Honda or vice-versa. This is because each manufacturer has a different communication system. The exception to this is OBD2.

What is OBD2?

OBD2 is a set standard across all car makers from certain years. OBD2 also set a standard 16 pin connection socket across all cars.  This standard was government enforced in the USA, the European Union (EOBD) and in other parts of the world such as Japan (JOBD) but is pretty much universal now.

If your vehicle is OBD2 compatible then an OBD2 reader/re-setter can be used on it. You plug your reader into the vehicle and it will display the fault codes or fault codes with their definition (depending on the equipment). For basic fault code readers, definition booklets or CDs are supplied for you to reference the code.

e.g. P0302 – Cylinder 2 Misfire Detected

Points to note about OBD2

-          It refers to the Engine Check Light Diagnostic system in a vehicle. The Engine Check Light is also referred to as the Malfunction Indicator Lamp (MIL). This covers pretty much most of the engine electronics, exhaust systems (emissions) and certain other parts of the vehicle chassis depending on the vehicle. Most vehicles will have fault codes stored without the MIL light even being on

-          OBD2 does not cover systems such as ABS (Brakes) or SRS (Power Steering) as these are still manufacturer specific and not catered for under the OBD2 standard.

-          Vehicles manufactured for the US market (regardless of make) had to be OBD2 compatible from 1996 onwards.

-          Vehicles manufactured for the European Union Market had to be OBD2 compatible from 2001 (petrol) and 2004 (diesel) onwards.

-          The above dates are guidelines but please realise that there are obviously cut off periods which cannot be catered for. For instance while a vehicle may have been registered early 2001 in the UK it may have been manufactured at the factory in 2000 and therefore may not be compatible.

-          To make things slightly more complicated, within OBD2 the communication systems can differ. However all our OBD2 diagnostic system cover all communication protocols including the latest CAN.

Are vehicles manufactured before these dates OBD2  compatible?

Yes, there are some models that are OBD2 compatible before the years stated above. These include many petrol Ford models in the EU going back to 1995/6. Some BMW models back to 1999/2000 etc. While early OBD2 compatible Fords used a standard 16 pin socket, BMW models before 2001 used a 20 pin BMW specific socket. So, for a 2000 BMW that is OBD2 compatible you would also require a BMW 20 pin adaptor to make connection possible.

I have a 16 pin socket does that make my vehicle OBD2 compatible?

No. Just having a 16 pin socket does not guarantee your vehicle is OBD2 compatible as many manufacturers used 16 pin sockets before this standard was implemented.

My Engine Check Light is not on – do I still have fault codes stored?

Your light does not have to be on permanently for there to be fault codes stored in your vehicle. Typically the light will only remain on if the fault is serious.

Are commercial vehicles covered by OBD2?

Under legislation this varies. In the EU commercial vehicles are not necessarily covered by law. However, you’ll find some manufacturers have implemented OBD2  on their light commercial range of vehicles.

If there is OBD2, is there an OBD1?

You will find the term OBD1 banded around.  This simply refers to any system before OBD2 was implemented. These were manufacturer specific and will vary.

If you are in any doubt about compatibility of any product with your vehicle, please contact us first before purchasing. Remember to include your vehicle model, year and engine type.