Custom OBD II Gauge in With OEM Look using arduino built a custom OBD II (on board diagnostics version 2 gauge in the clock of my Subaru BRZ (GT86, FRS) and a lot of people wanted me to build them one. Here is how you can build one of your own. My wife is about to give birth to our second son and all the code is open source, so I have nothing to lose by posting this.

(I still may sell the installation as a service or possibly the packaging of a kit in the future, but that won’t prevent others from using the open source pieces to do what they want in their own installations, other cars, other displays, etc. and frankly there is no money to be had in this. So, I’d rather share it with the DIY community at large.)

I’ll try to point out where I did things that are specific to my model of car and where you might want to change things to suit your needs. Hopefully this will allow others to build on what I’ve done.

The all important github link:

And more generically my code is here:

The car specific forum where all of this is getting discussed:

Custom OBD II Gauge in With OEM Look using arduino

Step 1: What you will need to do this (parts/tools/software/etc)

Parts (generic/specific):

-An Arduino or Arduino clone – I specifically use the adafruit pro-trinket for its small form factor and 5v logic.

-STN1110/ELM327 board. I chose the Sparkfun one because it is stable, uses UART for communication and doesn’t cost and arm and a leg.

-Assorted hookup wire

-128×32 SPI monochrome OLED display. I used the adafruit one. The ebay ones may work just as well, but I haven’t tested them.

-Your OEM clock. I used the OEM clock from a Scion FRS that I got on ebay.

-Some resistors (for the button setup)

-Optional – sensors (autometer oil temp, autometer oil pressure, acceleromter, pressure, temperature). I have some arduino code that will let you plug analog sensors into a system like this. I’ll make one of the “steps” pages about this.


-Soldering Iron

-Wire stripers

-Wire crimpers

-Helping hands


-dremel tool

Code libraries used:

-Arduino ELM327 library: . I thrashed around with the UART comms to the OBD II board for a long time. (you can see it in my crummy code for the 1.8” TFT version of this). This saved my project and my sanity.

-The Adafruit libraries for the OLED screen and tutorials: I love supporting this vendor as they always provide a lot of extras when you buy from them (support, working code (emphasis on working), tutorials, etc.)


Sublime Text2 Stino plugin (because real syntax highlighting is refreshing) –

the dot factory – for making monochrome bitmaps into arrays so you can display them on the screen (That’s how I got my icons)

windows paint – for drawing icons and splash screens

Custom OBD II Gauge in With OEM Look using arduino circuit

Step 2: Choosing your screen

I’ve been through several projects like this in the past and I have some advice to share on selecting a screen.

-You want the screen to fit in the OEM location with as little modification to the car as possible. I ended up measuring everything and cutting out templates on paper to see what would fit. For an old project similar to this I used a standard 16×2 character LCD. It fit perfectly in the GD Impreza’s clock location (

-You want as much support as you can get in terms of a graphics API. The adafruit stuff is awesome. Their TFT and OLED graphics API’s are great.

-You want the best visibility in all lighting conditions. Cars see night, day and direct sunlight to all their displays. OLED screens are great at this. Transflective LCD’s are also good at this. Reflective and Transmissive LCD’s are not good at all.

-Polarized sunglasses can sometimes ruin a great design if their polarization lines up the wrong way with the screen you select. Test things out before you dive into coding.


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