The On-Board Diagnostics II (OBDII) port is a crucial interface in modern vehicles, providing access to a wealth of data for diagnostics, monitoring, and performance tuning. A key aspect of the OBDII connector is its power supply, and understanding the concept of a “switched connector” is vital for many automotive applications, especially when integrating aftermarket devices.
One of the pins in the OBDII connector, specifically pin 16, is designated for battery power. In most standard OBDII implementations, this pin provides unswitched battery power, meaning it is constantly live as long as the battery is connected. This continuous power supply is intended for diagnostic tools and devices that might need to operate even when the vehicle’s ignition is off, for example, to read fault codes or monitor certain parameters.
However, for some aftermarket devices and specific installations, using this constant, unswitched power can be undesirable. Devices left permanently powered can contribute to battery drain over time, especially if they are not designed for ultra-low power consumption in standby mode. This is where the idea of a “switched OBDII connector” becomes relevant.
A switched OBDII connector, in essence, modifies or bypasses the standard unswitched power supply at pin 16, replacing it with a power source that is controlled by the vehicle’s ignition switch. This means the power to pin 16, and consequently to any device connected and drawing power from it, will only be active when the ignition is turned on.
Implementing a switched OBDII connector can be achieved in several ways. One common approach is to create a custom adapter cable. This involves intercepting the pin 16 wire and redirecting it to a switched power source elsewhere in the vehicle’s electrical system. A suitable switched power source is typically one that is active only when the ignition is in the “ON” or “ACC” position, such as circuits powering the radio or other accessory systems.
When creating such a modification, several important considerations come into play:
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Power Source Selection: It’s crucial to choose a switched power source that is robust enough to handle the current draw of the OBDII device being connected. Consulting vehicle wiring diagrams and device specifications is essential.
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Fusing: Proper fusing is paramount for safety. Both the original unswitched power feed (if still used for other OBDII pins) and the new switched power feed should be appropriately fused to protect the vehicle’s electrical system and the connected device from overcurrent conditions.
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Grounding: Maintaining a consistent and reliable ground connection is critical. It’s generally recommended to use a common ground point for both the OBDII device and the vehicle’s electrical system to avoid ground loops and ensure proper signal integrity.
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Connector Type: For custom cables, choosing appropriate and robust connectors is important. DSUB connectors, as mentioned in the original context, are a viable option for creating a durable and semi-permanent connection.
Alt text: OBDII connector pinout diagram illustrating pin assignments for various diagnostic protocols and power, highlighting pin 16 for unswitched battery power, useful for understanding OBDII switched connector modifications.
Modifying the OBDII power supply to be switched can be particularly useful for devices like performance tuners, data loggers, or telematics systems that are intended for regular but not constant use. By using a switched connector, users can avoid the risk of battery drain and ensure that these devices are only active when the vehicle is in operation.
In conclusion, understanding the Obdii Switched Connector concept is essential for anyone working with aftermarket automotive electronics. By carefully planning and implementing a switched power solution, users can enhance the safety and practicality of their installations, ensuring optimal performance and preventing potential electrical issues. Always consult with vehicle-specific wiring diagrams and consider professional installation if you are not comfortable working with automotive electrical systems.
