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11-23-2012, 08:39 PM
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#1
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,896
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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)
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-23-2012, 08:49 PM
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#2
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Join Date: Nov 2012
Location: Millstone, NJ
Posts: 641
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Flip a coin to decide haha. Id post this on lslt forum, there even alot of 4th gen dudes on here?
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94 TA GT. Stock 350, cam, exhaust
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11-23-2012, 08:50 PM
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#3
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,896
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Tech and I are not friends.
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-23-2012, 09:18 PM
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#4
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Stalker
Join Date: Aug 2004
Posts: 12,077
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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.
Last edited by V; 11-23-2012 at 09:18 PM.
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11-23-2012, 09:37 PM
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#5
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Join Date: Nov 2012
Location: Millstone, NJ
Posts: 641
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Even on ls1lt1.com?
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94 TA GT. Stock 350, cam, exhaust
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11-23-2012, 09:47 PM
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#6
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,896
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Quote:
Originally Posted by V
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.
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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.
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-23-2012, 10:14 PM
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#7
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Power Member
Join Date: Sep 2008
Location: Hackettstown, NJ
Posts: 1,632
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If I remember right, all the sensor grounds run to the PCM just to insure a clean signal.
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1998 Z-28 - SLP lid - Ported TB - LS6 Intake - Dynatech SS headers/Catted Y - Magnaflow Exh - 3.42 - Yank SS3600 - UMI weld-in subframe connectors, Adj LCA, Adj PHB, Q1A TA - Bolt-in Relocation Brackets - Strano springs - Koni shocks - 17" C6Z06 wheels - 326HP/335ft-lbs - 12.35 @ 110.41
Quote:
Originally Posted by Blackbirdws6
I can appreciate a dream but this person needed some real friends.
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11-24-2012, 11:40 AM
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#8
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Ayatollah of Rock N Rolla / Admin
Join Date: Mar 2006
Location: Parts Unknown
Posts: 12,573
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Quote:
Originally Posted by Dudbird113
Flip a coin to decide haha. Id post this on lslt forum, there even alot of 4th gen dudes on here?
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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.
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11-24-2012, 01:42 PM
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#9
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,896
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I am gonna cut the ground at the splice, and then solder it back into the circuit at the PCM
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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11-27-2012, 06:41 AM
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#10
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10 Second Club
Join Date: Feb 2008
Location: Eatontown
Posts: 1,647
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Get a rod and ground it right to the earth, this thing is never moving.
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1999 C5 FRC: 12.7@114
2008 TBSS: 12.48@108
2017 Silverado 2500 do you even lift breh?
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11-27-2012, 08:24 AM
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#11
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Mongo the Meet Coordinator
Join Date: May 2008
Posts: 16,896
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Quote:
Originally Posted by KirkEvil
Get a rod and ground it right to the earth, this thing is never moving.
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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...
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Quote:
Originally Posted by KirkEvil
repo bigals turd gen and part it out to a loving home
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