Does anybody know what this ground wires is for besides the pcm. Like what sensor is it for?

 

That is to insure that the PCM and the engine have are grounded to each other so that sensors like the coolant temp which ground through the block (water pump) will read acurately. Without it if the pcm has .7 Ohms on its gound and the engine has .1 Ohms on its ground the sensors reading would all be affected by .6 Ohms.

 

The ground is for:
PCM
oil level sensor
MAF
theft deterrent module
transmission range switch (auto)
fuel pump relay
instrument cluster
performance switch (if equipped)
traction control (if equipped)
ground to DLC

 

If this wire isn't getting a good ground would that stop the car from starting?

 

Some people have accidentally had it disconnected and it still ran, but of course, it should be connected.

 

I was just about to post asking about this same wire. I noticed mine was cut somehow while putting in a new trans and fixing a burned O2 wire on the same harness. Guess I need to ground this thing.

 

i would imagine they would share the common ground to provide accurate readings and to minimize the chances of any sort of voltage drop which would give false readings and throw off the computer