DIY ESP32 CAN Gauge

SimBa — Sat, 04 Apr 2026 15:06:40 GMT

I figured it was worth breaking this project out into it's own thread instead of burying it in my build thread.

Overview
A quick overview of what we're looking at here. A small ESP32 dev board with a built in display that is pulling ECU data via CANBUS. It's currently setup to use OBDII from one of the CAN headers on the Link G4x in my car. I drew and 3d printed a housing to mount it on the steering column.

Why
The CAN/OBDII data was already able to be picked up by my phone using a bluetooth dongle, but I don't always want to have my phone out to view temps. If I'm on track I like to be able to monitor temps without worrying about my suction cup mount flying off mid corner or my phone's battery dying. Further, this allows me to tweak what sensors I want to use and any parameters related to those.

Cost
Cost is probably the biggest pro for this setup for now. The electronics side is an ESP32 ( $23) board drawing power through a buck converter (5 for $10). The CAN signaling is run through a transceiver ($4 + shipping). So, not including the cost of the 3d printer, protoboards, wiring, etc... You're looking at around $30. With a basic electronics kit from Amazon and a couple bucks to find someone to print a housing I'd expect most people could get this done for ~$50.

What CAN It Do?
So far, I've only got it set up to read 4 different values, Coolant temp, Intake temp, Oil Temp and RPM. I've set the code up in a way that makes adding a sensor pretty easy, it's about 5 lines of code or so. Being OBDII, you are limited to the sensors defined in that standard as far as I'm aware. Link's CAN support is pretty extensive, but I wanted to get things up and running so using a predefined standard like OBDII seemed like the quickest path forward. The code is also set up to record the peak values for the sensor, which happens for each sensor, not just the currently displayed one.

The ESP32 board also has a lot of I/O. I've got this set up to drive green, yellow and red LEDs depending on the state of the currently selected sensor and some Good, Warning and Error values in the code. I didn't end up getting those LEDs installed in the current prototype, but I should be able to wire those in and be good to go.

Further, the ESP32 has Wifi and Bluetooth. I haven't ever used this board, so I'm not sure exactly how this would go, but I believe a small Android app could be created reasonably easily using something like MIT App Inventor to allow a phone to visualize all sensor data at once. I did something similar in college with an android phone and a temperature sensor on an Arduino, so I don't imagine this would be significantly different.

What Now
The housing will likely be redesigned a couple times. I've got a new faceplate on the printer next to me as I type this. After a test drive yesterday I realized that the current setup blocks more of the speedo and warning light cluster than I care for. I also would like to figure out some way to package the circuitry in the housing, as right now it's mostly just flopping around. Also, if LED's are added, I'd like to add a hole/slot for those, but that's a ways away.

I believe there's a bug in the code right now that causes some sort of segmentation fault and resets the board, which resets the peak values. I'll need to look into that. I also haven't fully explored the capabilities of the display or how quickly I can read from the ECU. I'm mostly looking for temps that change relatively slowly, but this is more important for something like RPM that changes quickly.

I don't have a huge desire to move on from OBDII, but I wouldn't mind being able to monitor some Link specific parameters. I don't believe OBDII has a Current Gear PID (there's something, but I think it's gear ratio, not Gear 1-6), which would be neat to hook up to a 7 segment display. This could happen in the future, but for now I think I'll focus on refining what I have.

Electronic dash using stock harness

Gee Emm — Fri, 03 Apr 2026 08:22:02 GMT

Currently looking to wire a Haltech IC7 dash to my ADM 2004 SE/MSM, replacing the cluster, fed from the Link but also needing inputs for lights, ABS, bag, blinkers, etc. Planning on tapping the existing cluster harness for those.

Option 1 - throw caution to the wind, cut the relevant wires, re-pin to a 6 or 8-pin connector, job done. Pro: not likely to want to go back so cut to the chase and do it the simple way. Con: going back messy, but unlikely.
Option 2 - splice in new wires leaving exiting wiring/plugs useable. Pro: best of both worlds, flexible into the unknown future. Con: Finniky, could have continuity problems.
Option 3 - de-pin relevant wires, cannabalise the spare harness for a suitable m/f connector pair for the relevant wires. Pro. Neat, reversable. Con: Doable? I don't know ...

So has anyone tried Option 3, on any connector on the stock harness? Are the pins uniform though the harness, I'm guessing not but is there any info out there?

Pending any thoughts and suggestions here, next week I will pull out that harness and do some playing around with it. I will also use the time to nail down exactly how many wires I am going to need, plus maybe a couple of spares.

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DIY ESP32 CAN Gauge

Electronic dash using stock harness