PCM Grounding Questions
Thread Starter
On The Tree
Joined: May 2022
Posts: 139
Likes: 6
From: Morgan Hill, Ca
PCM Grounding Questions Quick question regarding a wiring harness I am reworking for a swap (red/blue connector truck harness). Doing a standalone harness and am trying to simplify it as much as possible and keep it clean/hidden. As I am working through it, I'm finding that anything that is grounded (whether it be ground straps, black wires that connect to sensors/coil pack plugs/etc), all end up going to the following pins on the ECM: Blue 1, Blue 40, Red 1, Red 40.
All these various grounds join at different points in the harness and eventually go to those 4 pins on the ecm. My question is this: Can I cut these back close to the ecm, join all 4 of them, and run one large wire throughout the harness, which will then branch off where it needs to go? Could I theoretically also run only 1 grounding lug to the back of the cylinder head (rather than the 3 or 4 that are in the factory harness)?
Sorry if this has been answered, or is posted in the wrong section.
Thanks
All these various grounds join at different points in the harness and eventually go to those 4 pins on the ecm. My question is this: Can I cut these back close to the ecm, join all 4 of them, and run one large wire throughout the harness, which will then branch off where it needs to go? Could I theoretically also run only 1 grounding lug to the back of the cylinder head (rather than the 3 or 4 that are in the factory harness)?
Sorry if this has been answered, or is posted in the wrong section.
Thanks
On The Tree
Joined: Nov 2015
Posts: 132
Likes: 17
Here's my take on cutting harnesses, and which may apply in this case, and it appears you have the same concerns; the engineers that create this stuff invariably incorporate the not so obvious. Can't say what that might be in a case of the ground wires, but in my restomod project I never cut any ground wires and I added a bunch more to make sure I was able to get a dead short to the negative cable at the battery.
Nick
Nick
I have cut many factory GM harnesses for use in LS swap.projects. yes.. you can ground them all at one place.. what I do.. run a ground directly to the negative terminal on the battery that 9intersects with a body ground, and an engine ground.. all together. 10 gauge wire minimum to negative terminal on battery and you should be set. Ground all 3 together-frame, engine, and battery. That is the best way. Obviously the engine needs the negative terminal from the battery is attached directly to the engine block for adequate voltage to the starter. But after that. Ground all 3 together and you will be fine.
TECH Addict
Joined: Oct 2016
Posts: 2,513
Likes: 480
From: PDX-OR-USA
The separation of the ground wires is not always for day to day operation, it helps isolate noise and makes it so if a wire or connector fails it doesn't back feed.
To connect multiple ground wires (Or to provide sources to run the + side) I use a standard electrical piece sold for a electrical panel, they sell them relatively
cheap with 4 or many connections, all brass and I use a dab of electrical grease in each connection. you can also get them with a isolation base. Handy if you have multiple loads to split.
To connect multiple ground wires (Or to provide sources to run the + side) I use a standard electrical piece sold for a electrical panel, they sell them relatively
cheap with 4 or many connections, all brass and I use a dab of electrical grease in each connection. you can also get them with a isolation base. Handy if you have multiple loads to split.
Thread Starter
On The Tree
Joined: May 2022
Posts: 139
Likes: 6
From: Morgan Hill, Ca
The separation of the ground wires is not always for day to day operation, it helps isolate noise and makes it so if a wire or connector fails it doesn't back feed.
To connect multiple ground wires (Or to provide sources to run the + side) I use a standard electrical piece sold for a electrical panel, they sell them relatively
cheap with 4 or many connections, all brass and I use a dab of electrical grease in each connection. you can also get them with a isolation base. Handy if you have multiple loads to split.
To connect multiple ground wires (Or to provide sources to run the + side) I use a standard electrical piece sold for a electrical panel, they sell them relatively
cheap with 4 or many connections, all brass and I use a dab of electrical grease in each connection. you can also get them with a isolation base. Handy if you have multiple loads to split.
