EOBD (European On-Board Diagnostics) is, as the name suggests, a Europe-wide standard for electronic diagnostic testing.

We’ve had on-board diagnostics for several decades now and this really helps technicians to diagnose faults within the vehicle.

Modern vehicles are fitted with a plethora of microcomputers to control all of their various functions, and these are all interconnected.

In most cases, this is by a CAN (Controller Area Network) bus, which is simply a data highway within the vehicle’s electronic systems.

If a fault occurs in a system, it will usually log a fault code, which gives the technician a starting point from which to diagnose the problem.

EOBD systems do a lot more than just logging fault codes, though – they enable the clued-up tech to view live data from the vehicle, whether the fault is in engine management, ABS braking or any of the other systems.

A fault code reader, or a scanner, should be readily available and can be obtained pretty cheaply. For example, one of the supermarkets regularly has one for around £15. But its functionality is fairly limited – to engine management – and often focuses on emissions control systems.

These cheaper tools can be useful if you have a fault and your ’van goes into limp mode (the low-power, limited-speed condition that allows you to drive to a safer location), because you can often clear the fault code and restore full power.

As an example, a few months ago, I started up KC and had a fault light on the dash and no response to the throttle pedal. I plugged in the cheap scanner I keep in the ’van to read and clear the code – so far it hasn’t happened again.

One important point, though, is to write down the fault code before you clear it – that way, if another fault occurs that could be related, you can pass on the information about the first code to the technician, which can quite often lead to a far speedier diagnosis.

Deeper systems access via a fault code reader

Bear in mind that a cheap fault code reader won’t give you access to deeper systems, such as ABS, airbags or the BSI (Body Systems Interface), which controls functions such as side-light circuits, central locking and even the radio head unit. This is why garages spend thousands on the newest diagnostic kit.

The latest development is a blocking gateway on the EOBD port, to stop unauthorised access to the vehicle’s systems, which makes it more difficult for miscreants to steal it. This also means garages have to purchase an access code from the manufacturer, to access diagnostic features or even update on-board service data.

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