Diagnose car trouble with your PC

Computers are everywhere, including under the bonnet of just about every modern car.

In fact, almost all the mechanical and electrical functions of modern cars are controlled by software.

When you push the accelerator pedal in a modern car, for example, a signal is sent to the computer, which then increases the power of the engine.

When sophisticated electronics were first introduced into cars, they were not easy for someone who didn’t work for the car company or a dealer or mechanic to access. The car manufacturers began to sell equipment that could read information from these boxes, but it was designed for garages to use. This meant it was bulky, expensive and designed to work with only one type of car.

Fortunately, as car computers have evolved, so has the equipment used to read from them. Standards have been developed and you can buy many inexpensive gadgets that enable you to connect your PC to your car. You can turn off the engine diagnostic light, tune your car or even switch on hidden features.

Why fix it yourself?
If you’re interested in cars and how they work, the idea of learning more about what goes on under the bonnet is very exciting. Even if you see a car only as a way to get around, though, there are sound financial reasons for wanting to connect your car to your computer.

Most cars have a check engine light that illuminates when the its computer notices a problem. Sadly, this light rarely gives further details on what needs attention. Normally, if this light appears you’ll need to make an appointment at a local garage and take your car in for a service.

The garage will determine what needs to be fixed, but even if it’s an extremely simple job, such as tightening a loose fuel filler cap, you can expect to be handed a bill.

If you have a computer, the whole process can be much simpler. When the light appears a computer can be used to instantly diagnose the fault. If it’s something that requires professional attention you’ll still need to contact a garage, but if it’s easy to fix ­ such as a loose fuel cap ­ you can do so yourself, saving time, hassle and money.

An excellent example is the recent situation when too much silicone appeared in UK petrol supplies, triggering a warning light in many cars. Those with a DIY tool were able to diagnose the problem and fix it themselves while others had to pay.

Car connection kits allow you to do more than troubleshooting. It is possible to track the performance of the vehicle and then apply this knowledge when servicing the car. It can also be possible to tune the engine, getting more performance by tweaking the way that it is controlled by the car’s computer.

Will your car connect?
Before buying a car connection kit, you need to know whether your car will be compatible. By the mid 1990s, devices known as Electronic Control Units (ECUs) were being fitted in many cars.

These units have dozens of sensors that gather information such as the coolant temperature, throttle opening and oxygen level in the exhaust.

They can then use this data to tune the engine by altering the ignition timing, how long the fuel injectors stay open and so on.

This in turn controls the car’s emissions, economy and performance. Unfortunately early car ECUs have no standard interface, so getting at the data they contain can be a problem.