OBD2 scanners are incredibly useful tools for modern car owners. They offer a peek into your vehicle’s health, allowing you to read diagnostic trouble codes, monitor performance data, and even clear minor error codes yourself. This convenience leads many to wonder: can I drive with an OBD2 scanner plugged in?
The short answer is generally yes, you can drive with an OBD2 scanner plugged into your car’s diagnostic port. The OBD2 port, a standard feature in most cars since the mid-1990s, is designed to provide constant power through pin 16, regardless of whether your ignition is on or off. This constant power supply is a requirement across all OBD international standards to ensure diagnostic tools can communicate with the car’s computer system at any time.
However, just because you can drive with it plugged in, doesn’t necessarily mean it’s always the best practice. Leaving an OBD2 scanner connected means it will be continuously drawing power from your car’s battery. While the draw is typically minimal, often around 10mA or slightly more, it’s still a constant drain. Think of it like a tiny trickle; over time, even a small current draw can impact your battery’s charge, especially if your car sits idle for extended periods.
To put it in perspective, this extra drain from a plugged-in OBD2 device could increase your car’s total sleep consumption. If your car normally draws 30mA when off, a 10mA draw from the OBD2 scanner brings it to 40mA. This might seem insignificant, but it could reduce your battery’s effective lifespan. If you drive your car regularly, a couple of times a week, you likely won’t notice any difference. However, if your car sits unused for weeks or a month at a time, this consistent drain could lead to a noticeably flatter battery sooner than expected.
You might notice that some OBD2 apps or scanners appear to be inactive when the car’s ignition is turned off. This is often because they employ clever power-saving techniques. One common method is voltage sensing. These devices monitor the battery voltage and go into a sleep mode when the voltage drops below a certain threshold, typically around 13.2V. This voltage level usually indicates that the alternator isn’t running and the car is off. In sleep mode, they minimize their power consumption but remain connected and monitor the voltage, ready to “wake up” when the car is started again. Even in sleep mode, these devices are still drawing a small current to maintain this monitoring function.
It’s also worth noting that some car manufacturers, like BMW, have incorporated additional features into their diagnostic ports beyond the standard OBD2 protocol. For example, BMW uses pin 15 for switched power. This BMW-specific implementation is used by advanced diagnostic tools like INPA to detect when the ignition is switched on. However, this is primarily relevant for specialized diagnostics and doesn’t change the fact that pin 16 remains permanently live for all OBD2 compliant devices.
So, while driving with an OBD2 scanner plugged in won’t cause immediate harm and is generally safe from a functional perspective, the continuous battery drain is a factor to consider. For daily use and short periods, the impact is negligible. But for vehicles that are not driven frequently, or if you are particularly mindful of battery longevity, it’s a good idea to unplug your OBD2 scanner when it’s not actively in use, especially if the car will be sitting for several days or weeks. Unless you are actively monitoring your vehicle or using a feature that requires the scanner to be constantly connected, disconnecting it when you park up for extended periods is a simple step to minimize unnecessary battery drain and ensure your car is ready to start when you need it.
