I’ve been looking at car instrument clusters (this one’s out of a 2010 Toyota Hilux). The circuitry to drive some indicator LEDs (eg. for low oil pressure, check engine, brake etc.) is a common 12v positive supply with the ECU (or sensor) providing the path to ground via a current limiting resistor (on another part of the PCB, not shown in the pic). There is a capacitor and resistor in parallel with some of the LEDs and I’m curious as to what this would be for? For some LEDs there is no capacitor or resistor, for others there are both or only the capacitor or resistor.
If I was guessing it might be ESD protection? Or to prevent capacitive coupling causing the LED to light from neighbouring traces (unlikely at this voltage?)
Anyone know or care to hazard a guess? It might be related to how each LED is driven (eg. by ECU or by a simple switch like oil pressure)…