How to diagnose a check engine light

An engine warning light is always cause for concern, but if you could determine the problem instantly at the side of the road, wouldn’t that alleviate some of the worry?

Modern cars are much better at telling us what’s wrong with them. Thanks to standardisation of engine management protocols and the connection, one device is now able to read almost all makes and models.


On-board diagnostic readers, such as the ELM 327, are available on eBay for as little as £4. These can connect to your smartphone via Bluetooth.


Engine Faults

With an application such as Torque installed on your phone, you can view your engine fault code and diagnose the issue in minutes.

Garages are known to charge an hour’s labour just for checking your fault codes and resetting the warning light. If you’re armed with this information, you can ask them for a quote on the fix beforehand. You can also remove the fault code and warning light yourself if you’re a capable home mechanic.


Torque Application

For the enthusiast, diagnostic applications offer a wealth of information on your car’s vital statistics, not usually reported on the dashboard. These include intake manifold temperature, C02 emissions, and turbo boost pressure. They can also log data and offer deeper insights into your fuel economy over different journeys.

Used on a track day, Torque can estimate 0-60 and 1/4 mile times. With the graph functions you can log engine performance throughout a lap, in a way you might only have seen in professional racing a decade ago.


Focus OBD2

Finding your OBD slot is usually easy enough with most manufactures concealing them somewhere below the steering wheel or in the centre console. Smaller OBD readers are designed to be left plugged in, if required. Insurance companies have been using readers in this capacity to offer lower premiums to safer drivers for some years now.

Given their price and relative ease of use, there really is no reason not to own one. Unless you prefer to hear bad news from your mechanic…