PCM vs. Chassis Ground
 

Pulling out the 60e and VSS wiring from the main engine harness, and need to know if the ground needs to be a "PCM" ground, or can I ground in at a chassis ground?

AFAIK, its for a "temp" sensor..
"PURPOSE
The Transmission Fluid Temperature (TFT) sensor is a thermistor (a device that changes resistance according to changes in temperature) used to indicate transmission fluid temperature. The Powertrain Control Module (PCM) uses the TFT sensor signal input to determine the following:


Torque Converter Clutch (TCC) apply and release schedules
Hot mode determination
Transmission shift quality

OPERATION
High sensor resistance produces high signal input voltage which corresponds to low fluid temperature. Low sensor resistance produces low signal input voltage which corresponds to high fluid temperature. "

Options being; 1) leave it alone, 2) cut it and splice it, or 3) cut it and ground it chassis wise.

Book does not show it as a chassis ground. Shows the sensor ground circuit as black wire leaving PCM pin B6 then hits splice S122 (25 CM from PCM) where it goes 3 ways. One black to tranny pin M, one black wire to ECT (Coolant temp in WP) pin A, and one black to TPS pin B.

(PCM will be in car, and trans harness is going through tunnel)

Flip a coin to decide haha. Id post this on lslt forum, there even alot of 4th gen dudes on here?

Tech and I are not friends.

can you check for continuity between the normal pcm to chassis ground and the B6 pin?
if off, and you have continuity(very low, if any, Ohm resistance) then you know it will act as a ground regardless if the pcm is switched on or not. if you have no continuity when pcm is off, then it would mean B6 is a switched ground. if its switched, i would run the sensor wires both to the pcm, if its not switched by pcm, then id say just run a new chassis ground and just check to make sure you have a good ground connection.

Even on ls1lt1.com?

That was my plan, just wanted to hear some opnions on this.

As long as its not a switched ground, which it would be very doubtful being a shared ground, a ground is a ground as long as signal stays clean.

If I remember right, all the sensor grounds run to the PCM just to insure a clean signal.

This literally made me LOL. Thanks for the grins man.

Matt, according to your description it sounds like it needs to be a PCM ground.

I do not know if GM PCMs are this sophisticated but I know in some cases a shared ground is necessary for proper device code operation.

I am gonna cut the ground at the splice, and then solder it back into the circuit at the PCM

Get a rod and ground it right to the earth, this thing is never moving.

Would not work as the rest of the car is not grounded that way. Didn't you graduate as an engineer? Too much HR work...