If your engine-management warning light comes on or your car isn't performing correctly, you usually have no option but to ask a dealer to connect it to a diagnostic computer to find the fault. The TurboGauge (£129 from mavericktechnology.co.uk) can diagnose problems in your engine and assess its performance. The gauge plugs into the same EOBD (European on-board diagnostics) socket on your dashboard as a mechanic uses. If there is a problem the TurboGauge can detect, it shows the fault code. Once the problem has been solved, the device deletes the error message from the engine management chip and resets the warning light - operations that a dealer may charge for. It can also display data such as your 0-60mph time and store 300 hours of engine information.