1Gps OBD2 Dual System: OBD2 only be available for vehicles produced after 2008. Gps Model Perfect Suitable for All Vehicle. ( If your car is not compatible with Obd mode, please use Gps mode. Dual System, Change free. OBDll mode is not compatible with hybrid electric vehicle, diesel car, pickup truck, Rv, computer modified car. If the speedometer shows only voltage after turning on the power, please switch to Gps mode. 2Features: Obd+Gps+ Slope meter+Ambient light (blue, red, purple switching)+12 language settings (English, Chinese Simplified, Chinese Traditional, Thai, Japanese, Korean, Russian, Arabic, Malay, Spanish, German, French), making driving safer and easier. 3Clear Intuitive Display: The tachometer's analog display has a pointer that moves to indicate Rpm, so you can visually identify the engine Rpm value. With multiple display screens, you can switch to your preferred screen at will. The digital speed readout is easy to see at a glance, so you can concentrate on driving without looking down at the dashboard, avoiding distractions and even accidents. Some can also display various values such as speed, altitude, water temperature, and voltage. 4Fault Codes Clearing and Acceleration Testing: When the engine warning light in your car's instrumentation comes on, it indicates that something is wrong with the car, but with the P21 speedometer, you can clear the codes yourself without having to spend money to the repair shop. There's also an acceleration test and a brake test so you can get a better idea of your car's performance. 5Multiple Fault Alarm Functions: Obd mode can perform overspeed alarm, speed alarm, water temperature alarm, voltage alarm, tilt alarm; Gps mode can perform overspeed alarm, low voltage alarm, tilt alarm, etc. The chip with powerful performance and compatibility to make sure dual system, dual?run memory and dual?core processor high?speed operat.