ECU Grounds clarification

[ellisd1984]

Hi Hopefully this one will e relatively quick.  To someone confirm off the 5 grounds on the ST205X which ones would go to the engine and which ones are sensor grounds?

https://drive.google.com/file/d/1xdWj-UbhhMPSc3X8XG5zAbv-KnnFkmKk/view?usp=share_link

https://drive.google.com/file/d/1gih1FLBDfTcnUts056UyOD-5Fou44Tzf/view?usp=share_link

Are the 5v and Sensor grounds on the expansion loom brought from the same source as the main ECU pins? or is there a second feed?

From what I've read I'm ok converting the Toyota speed sensor to a 5v feed.  Would I then need to ground this to sensor ground instead of the existing arrangement that grounds to the engine/chassis?

https://drive.google.com/file/d/1XXLfIiY6CALhFM9O9uj5lvV56Ht0b1_4/view?usp=share_link

[Adamw]

Most toyotas from around this era didnt really use separate sensor and power grounds logically, most of the high current noisy stuff was sort of passed through its own dedicated wires, but there were often odd practices such as the O2 sensor and knock sensor grounding through the chassis/block or high power ground connections.   Effectively all grounds are common in both the factory ecu's and our plug-in, but "sensor grounds" are routed differently internally to minimise high power noise effects on analog signals. 

Using Link pin numbering, we have Pin 1 and 14 routed as the high power grounds, 23, 26 & 46 as sensor grounds.  

For a digital speed sensor the ground is not important as all your signal needs to do is cross the ~1.8V threshold, we are not trying to measure anything accurately.  

[ellisd1984]

Thanks Adam , that clears things up