12VIO Fail & Dirty Power

I’m using the M2 in my 1995 Jeep Wrangler to drive the speedometer and tachometer along with an OLED display. I also drive the fan relays. I read data from the J1850 bus to drive everything.

It all works great on the bench, but I’ve been having issues in the vehicle. Most notably, the tach and speedo would stop working randomly. I had to cycle power to the M2 in order to get it back. The display never stops working when this happens. It happens most of the time when I turn on the turn signal. The O-scope showed a lot of noise coming from the B+ connection when the turn signal was on. Does anyone have a standard power supply or filter they use in the vehicle to power there M2. I might just try using a capacitor to see how that works.