The unit can only be installed in a ar with a 12 V DC power supply, negative ground 
If you connect the ignition wire (red) and the battery wire (yellow) to the car chassis
Disconnect the battery's negative terminal and make all electrical connections before installing the unit.
Insulate unconnected wires with vinyl tape or other similar material. If no connections are made, do not let the wire come out from the tab to prevent short circuit.
Be sure to ground this unit to the car's chassis again after installation.
If your car's ignition does not have an ACC position, connect the ignition wires to a power source that can be turned on and off with the ignition key. If you connect the ignition wire to a power source with a constant voltage supply, as with battery wires, the battery may die.
Do not use your own screws. Use only the screws provided.
Install this unit in the console of your vehicle. Make sure the faceplate will not hit the lid of the console (if any) when closing and opening.
After the nit is inst lled, check whether the brake l mps, blinkers, wipers, etc. on the car are working properly.
Mount the unit so that the mounting angle is 30° or less.
If the fuse blows, first make sure the wires are not touching to cause a short circuit, then replace the old fuse with one that has the same rating.
Connect the speaker wires correctly to the terminals to which they correspond. The unit may be damaged or fail to work if you share the 
When only two speakers are being connected to the system, connect the connectors either to both the front output terminals or to both the rear output terminals (do not mix front and rear).
Do not touch the metal part of this unit during and shortly after the use of the unit. Metal part such as the heat sink and enclosure become hot.
Mounting and wiring this product requires skills and experience. For safety's sake, leave this work to professionals.KDC-4051URY, KDC-415UA, KDC-455UW, KDC-415UR, KDC-4051UR specifications
The Kenwood KDC series of car audio receivers, including the KDC-4251URY, KDC-4051UG, KDC-4451UQ, KDC-4651URY, and KDC-4551UB, represents a significant advancement in in-car entertainment technology. Each model offers a set of unique features while adhering to Kenwood's reputation for high-quality audio performance and user-friendly design.The KDC-4251URY is noted for its powerful 50W x 4 amplifier, providing ample sound for any vehicle. This model incorporates a high-quality FM/AM tuner, ensuring crystal-clear reception. One of its standout features is the Enhanced Audio Control, which allows users to fine-tune sound settings, including a 3-band parametric equalizer. Furthermore, it supports USB playback for both MP3 and WMA formats, giving users the flexibility to enjoy their music library seamlessly.
The KDC-4051UG focuses on connectivity and versatility. This model also includes a 50W x 4 amplifier and features a front USB port, which is ideal for connecting smartphones and USB drives. Its Bluetooth integration offers hands-free calling and wireless audio streaming, making it a practical choice for technology-savvy users. Enhanced compatibility with various audio formats ensures that most media libraries are supported.
The KDC-4451UQ takes the user experience a notch higher with its dual USB ports, allowing for simultaneous connections. Additionally, it features a built-in Alexa voice control compatibility, offering drivers a hands-free way to manage their playlists and receive directions without taking their eyes off the road. The variable color illumination provides customizable aesthetics to match any vehicle interior.
The KDC-4651URY comes equipped with a larger display, which enhances visibility and ease of use, especially while driving. It supports HD Radio, significantly improving sound quality for digital broadcasts. Additionally, it features advanced sound retriever technology that enhances compressed audio files, making them sound clearer and more dynamic.
Finally, the KDC-4551UB stands out for its compatibility with Android Auto and Apple CarPlay, allowing for seamless integration with mobile devices. It has a rear camera input for added safety and provides users with a clearer view and additional assistance while reversing.
Each of these Kenwood models showcases a commitment to sound quality, advanced technology, and user-friendly interfaces, making them excellent choices for anyone looking to upgrade their in-car audio experience. Whether it’s about enjoying personalized playlists, making hands-free calls, or simply experiencing superior audio clarity, the Kenwood KDC series caters to a variety of needs and preferences.