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Old 12-31-2012, 11:38 PM   #1
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Default pcm ground

question is, is there a logical reason the LT1s stock pcm ground doesn't just run to the main ground distribution stud on the passenger fender?

why does it ground to the block?

is it a bad idea to run it to the stud instead? it's right there.. seems too convenient...
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Old 01-01-2013, 11:55 AM   #2
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Should work either place, My guess is there for convince of harness design. Here is a pic of wire on the harness. http://shbox.com/1/harness3.jpg It won't reach the wheelwell stud unless you'r building a custon harness. Engineers probably put there to shorten wire run, the black wire goes to a splice (s109) in harmess up near the PCM where it breaks out and feeds 2 pins in PCM, oil lever sensor, MAS, and then goes inside to dash through P110 and another splice that feeds a bunch of other things.
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Old 01-01-2013, 01:40 PM   #3
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ahh i guess you're right, i forgot how it used to look.. that does make sense for routing

i deleted my level sensor and ran the maf ground to a chassis ground stud; so i forgot it used to be connected to those, there are no actual chassis ground pins running through my harness anymore

this wiring harness is hilarous, but i see where he went wrong now:

- he ran the ground stud to a dirty oil pan bolt, and had issues not having good ground
- decided.. screw it, lets just make a new ground harness so i know its ok
- pulled the two pcm/sensor ground pins instead of the chassis ones, leaving the sensor grounds disconnected completely
- ran the new chassis ground harness to the pcm/sensor ground pins



it felt so good putting it back together right!
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Old 01-01-2013, 01:52 PM   #4
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woah woah wait a minute here

where does the chassis ground go through P110?

the only ground i have running via the engine harness is through C210, which is labeled fuel pump ground feed (pin C)

did i miss one!?
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Old 01-03-2013, 11:00 AM   #5
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Looks like you had a good mess to clean up... I just noticed you'r a '97 I was looking at my '95 service manual ground distribution. Your OBD1 got me distracted . On the '95 after splice S101 in engine harness, black/white wire basically leaves the engine harness goes through firewall grommet P110 to under dash connector C210 pin 'B' and hits a body harness splice S215 and blk/wht wires go to 5 to 6 places depending on model,etc. (ALDL, TDM, A4 Tranny position sw, fuel pump relay pin 'A', instrument cluster, TCS).
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Old 01-03-2013, 11:07 AM   #6
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ohh ok the black/white to C210, yeah i didnt miss that one..thanks for clarifying
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