In this article I detail the steps I took to add a power switch to a OBD2 Bluetooth engine scanner. It stays plugged in to your car’s engine reader at all times, but I wanted the ability to turn it off when not in use so that it did not drain the battery.

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I didn’t want my OBD2 engine monitor draining the battery when the car was off, so I decided to put an on-off switch on it. In this post a go through the details of how to add an inexpensive switch.

Another reason you may want a switch to to be able to turn off your engine monitor when not at work (if your employer uses such a device to monitor your driving).

If you don’t mind spending about $10, an easier alternative is to just add in an extension with a switch built right in.

Update (2020 December): Use this OBD Bluetooth adapter and the Torque App (Android or iOS) to monitor your vehicle.

I bought this Bluetooth OBD2 engine monitor   off of Amazon for about $20. It stays plugged into your car’s engine diagnostic port at all times, and communicates through an app to your phone.

Alright, let’s get started!

Step-by-Step Procedure

The first step was to remove the sticker on top, then remove the 4 Philips screws.

The two halves are glued together, so carefully pry the two halves apart, and take a look inside.

I read somewhere that you could just rewire it so that the wire going to pin 16 was changed to now go to pin 8. That way the unit would only get power when the car was on. That did not work for me. So instead, I put a switch between pin 16.

I found an on/off switch off of an old broken desk lamp. Some switch like this would work.

Here is a close up view of what that wiring modification looks like:

I put a little heat shrink on there to protect the wiring.

Then I cut a rectangular hole in the back of the unit for the switch to fit in. I used a Dremel tool to cut the hole in the casing.

Then fit the two halves back together and put the 4 screws back in.

This thing now plugs into the car, and you can turn it off if the car will be sitting for a while.

After going through all this, I use the Dash Android app (update 2020 – The Dash App is no longer available on the Google Play Store) to monitor the engine while driving. It actually works fairly well.

Update: Use this OBD Bluetooth adapter and the Torque App (Android or iOS) to monitor your vehicle.

But if I were to do it all over again, I would consider getting this “BlueDriver” OBD2 engine monitor, which is a higher quality unit with a few more bells and whistles.

Thanks for reading. Click this article for more information on this and other OBD2 monitors.