Meet Carly

Back in the good old days, if you were looking to diagnose a problem with your car you simply hit the various parts with a hammer until it started to work again. Since then, electronic gubbins like ECUs and fuel injection systems have taken over and DIY mechanics have complained endlessly about these ‘black boxes’ taking away their ability to tinker. Well, fret no more.

German software developer Carly – that’s the name of the company, incidentally – has produced a series of apps for BMW, Mercedes, Renault and most of the VAG brands. These allow you to connect to the car’s diagnostic port via a tablet or smartphone, making it possible to read and clear error codes, as well as carrying out basic coding.

I decided to have a go with the Android version of the BMW app on my E46. A 16-year old car isn’t perhaps the best platform to show off the capabilities of the software – compared to a modern machine it’s still comparatively gubbins-free – but in fact the app support goes right back to the E36. It covers all the major BMW Group models since then, including the MINIs from 2006 onwards.

Getting started is simplicity itself. The app isn’t cheap at £54.99, but you simply purchase your copy via the app store and order an adaptor cable direct from Carly for £44.90 (in the case of the Android version). Armed with the app and the cable you plug into the diagnostics port, enter a couple of details about your year and model then get started. Some versions even come with a wireless adaptor so you don’t have to mess around with the cable.

To my slight alarm, the first time I plugged it in, the app registered no less than 21 different fault codes that I never knew were there. (This is a car that runs perfectly and never has any untoward lights on the dashboard.) After a reset, all bar one of them went away. The lingering malfunction was reported as ‘00003D – lambda probe heater after cat bank 2’. A little bit of digging revealed this means one of the post-cat lambda sensors needs replacing.

Access to the diagnostics information is probably the most useful function for an older car, but there are plenty of other features. Should you wish, you can reset the service indicator following home maintenance. You can also access and log real-time sensor data for things like VANOS activation and mass air flow to aid fault diagnosis. And you can view the car’s mileage history including a ‘highest recorded mileage’ figure that could be used to detect tampering (fortunately mine tallied with the instrument cluster).

Intriguingly, the app allows you to ‘code’ various software functions into the car. This is simply a question of ticking or unticking boxes to enable optional features. Most of it is fairly trivial stuff like whether or not the indicators flash when the alarm is activated, but even on an older car there is plenty to play around with.

The bottom line is the more recent the car is, the more that Carly can do. Some models will allow you to alter your iDrive settings, perform service regenerations on diesels equipped with particulate filters or manually open and close the exhaust flap on the high performance petrols. Driving an E92 M3 with the exhaust flap permanently open must be worth the cost of the app alone. But as my hidden lambda sensor fault proves, even on the earlier cars it’s a useful tool to have.