Grounding/Negative side work.
Junior User
Joined: Sep 2005
Posts: 54
Likes: 1
From: Southern California
I have a 2004 F250, and after reading through this thread, I was wondering how many people were successful with using the passenger side cable, 3C3Z14301BA, on the driver's side negative battery post? Would a 1/0 cable between the frame and engine block be just as beneficial?
Thanks, in advance.
Thanks, in advance.
2nd Gear
Joined: Jun 2025
Posts: 2
Likes: 1
Grounding to FICM and PCM
Hello,
I have been watching your videos and they are a great way to learn the ins and outs of the 6.0 negative power flow. I am looking to implement this system into my 6.0 my question is, when you are grounding to the FICM and PCM grounding points from the driver side negative terminal to the body tub, are you utilizing the cables in series or are you placing two separate ground cables on the negative battery terminals? Also are you aware of any issues if the cables are ran in series? I am somewhat new to this thread so trying to ensure I fully understand the implementation prior to utilizing it myself.
I have been watching your videos and they are a great way to learn the ins and outs of the 6.0 negative power flow. I am looking to implement this system into my 6.0 my question is, when you are grounding to the FICM and PCM grounding points from the driver side negative terminal to the body tub, are you utilizing the cables in series or are you placing two separate ground cables on the negative battery terminals? Also are you aware of any issues if the cables are ran in series? I am somewhat new to this thread so trying to ensure I fully understand the implementation prior to utilizing it myself.
Last edited by where'sthepedal?; Jun 22, 2025 at 07:33 PM.
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Hotshot
Joined: Dec 2014
Posts: 17,762
Likes: 3,053
From: Jersey Shore
I've run a single cable to both points by stripping the insulation off the single cable where the FICM connection is, using a larger terminal (maybe a 4ga) for the folded wire to attach at the FICM ground, then let the wire continue to the firewall ground. That takes some work.
However, I've also used two cables: one from the battery to the FICM ground, and another from the FICM ground up to the firewall. That's what I have right now. There will be a milliohms increase in resistance at the firewall due to the connection at the FICM point, but it will not matter.
However, I've also used two cables: one from the battery to the FICM ground, and another from the FICM ground up to the firewall. That's what I have right now. There will be a milliohms increase in resistance at the firewall due to the connection at the FICM point, but it will not matter.
2nd Gear
Joined: Jun 2025
Posts: 2
Likes: 1
Thank you for the break down I appreciate the help, that is the way I understood it from the video breakdown. I wanted to have a full understanding of the run before I installed it myself, I appreciate all the help.
Cargo Master
Joined: Nov 2015
Posts: 3,366
Likes: 915
From: Fort Worth, TX
No problem. When I wrote technical reports on tests I ran my director often would tell me no one outside of those who would normally receive the reports would have a clue of what I was saying. And where I am now I'd redo all the older videos.
Oh, and my voice is still breaking up....
I started out with the objective of getting both batteries to work in harmony, so their life was extended and we had the best voltage during starting. And that's still a valid goal. Ford designed the system around the passenger battery being the main battery, and the driver battery as the support or auxiliary battery to support a diesel's higher starter loads. But in the design of just being support, they approached it as an add-on. The battery pack should have been designed as a pair or system. OTR trucks, transit busses, and all large Diesel engine vehicles have the voltage supply designed in a more balanced manner. But for an ideal system, it will take a good $300-$350 to redo the entire cabling. That's fine if you're cables are in need of replacement, but the system works OK and with a few dollars we can improve the balance.
By installing an additional ground cable in the drivers battery circuit we can get an improvement. The cheapest way is to install 18" of 1/0 cable from the drivers negative termination at the frame to the engine. A little more expensive and better version is to install the factory cable that is used by the dual alternator vehicles. It's the same cable used on the passenger side, a 1/0ga from the battery terminal to the engine block, with a not really need leg to the frame. If you are making your own cable it can be a battery terminal on one end and a lug on the other connected to the block.
There also should be an improvement on the positive battery to battery link, and this can be a 2ga cable to simplify the discussion 70" long eye to eye with1/4" lugs on the ends. in hind site for everyone across the country, I could have just said a 1/0ga for the coldest temps, but I was trying to lessen the cost for those not needing it.
So very basic:
2ga 70" eye to eye, 1/4" lugs, positive.
1/0ga 18" eye to eye, 1/2" and 3/8" lugs, negative.
Upgrade to that:
1/0ga 70" eye to eye, 1/4" lugs, positive.
1/0ga 38" Battery negative terminal to 1/2" eye, lug, negative.
Doing that gets you a (relatively) balanced battery pair for starting loads. There are some losses on the negative side that feed the electronics due to the negative small gauge cables to the body tub. That can be addressed with an inexpensive 6 to 8ga cable run from the drivers negative terminal to the FICM/PCM/CJB grounding points.
So, here's the kicker. With the stock battery cabling the drivers battery doesn't see as much of a battery voltage drop as the main or primary battery on the passenger side. You can actually improve your voltage to the FICM and PCM during the starting event by using an 6ga negative cable from the drivers negative terminal to the fore mentioned FICM/PCM grounding points (or the driver's inner fender) and removing the 8ga cable off the passenger battery. With the stock cables the driver's battery is somewhat isolated from the starters big draw. And that's the video I can't finish right now.
It's actually a tough call what to do. We are not talking a huge differential, but then we get kind of crazy with big cables and big alternators that actually do less then these.
6ga 30" cable 1/4" eye to 1/4" eye, battery to ground 1
6ga 18" cable 1/4" eye to 1/4" eye, ground 1 to ground 2.
Hell, this is probably still confusing ........
Oh, and my voice is still breaking up....
I started out with the objective of getting both batteries to work in harmony, so their life was extended and we had the best voltage during starting. And that's still a valid goal. Ford designed the system around the passenger battery being the main battery, and the driver battery as the support or auxiliary battery to support a diesel's higher starter loads. But in the design of just being support, they approached it as an add-on. The battery pack should have been designed as a pair or system. OTR trucks, transit busses, and all large Diesel engine vehicles have the voltage supply designed in a more balanced manner. But for an ideal system, it will take a good $300-$350 to redo the entire cabling. That's fine if you're cables are in need of replacement, but the system works OK and with a few dollars we can improve the balance.
By installing an additional ground cable in the drivers battery circuit we can get an improvement. The cheapest way is to install 18" of 1/0 cable from the drivers negative termination at the frame to the engine. A little more expensive and better version is to install the factory cable that is used by the dual alternator vehicles. It's the same cable used on the passenger side, a 1/0ga from the battery terminal to the engine block, with a not really need leg to the frame. If you are making your own cable it can be a battery terminal on one end and a lug on the other connected to the block.
There also should be an improvement on the positive battery to battery link, and this can be a 2ga cable to simplify the discussion 70" long eye to eye with1/4" lugs on the ends. in hind site for everyone across the country, I could have just said a 1/0ga for the coldest temps, but I was trying to lessen the cost for those not needing it.
So very basic:
2ga 70" eye to eye, 1/4" lugs, positive.
1/0ga 18" eye to eye, 1/2" and 3/8" lugs, negative.
Upgrade to that:
1/0ga 70" eye to eye, 1/4" lugs, positive.
1/0ga 38" Battery negative terminal to 1/2" eye, lug, negative.
Doing that gets you a (relatively) balanced battery pair for starting loads. There are some losses on the negative side that feed the electronics due to the negative small gauge cables to the body tub. That can be addressed with an inexpensive 6 to 8ga cable run from the drivers negative terminal to the FICM/PCM/CJB grounding points.
So, here's the kicker. With the stock battery cabling the drivers battery doesn't see as much of a battery voltage drop as the main or primary battery on the passenger side. You can actually improve your voltage to the FICM and PCM during the starting event by using an 6ga negative cable from the drivers negative terminal to the fore mentioned FICM/PCM grounding points (or the driver's inner fender) and removing the 8ga cable off the passenger battery. With the stock cables the driver's battery is somewhat isolated from the starters big draw. And that's the video I can't finish right now.
It's actually a tough call what to do. We are not talking a huge differential, but then we get kind of crazy with big cables and big alternators that actually do less then these.
6ga 30" cable 1/4" eye to 1/4" eye, battery to ground 1
6ga 18" cable 1/4" eye to 1/4" eye, ground 1 to ground 2.
Hell, this is probably still confusing ........
Lead Driver
Joined: Jul 2004
Posts: 6,949
Likes: 510
From: Foothills, CA
I was just looking for the diagram on grounding points on the block, started reading through the thread, and found this. I don't remember any discussion about removing any grounding cables. Is removing the 8ga cable from the passenger battery necessary, or worse, detrimental if you don't?
Lead Driver
Joined: Jul 2004
Posts: 6,949
Likes: 510
From: Foothills, CA
You and Les have any interest in going camping in a slide in truck camper? That is on the back of a truck with under 32K MILES? PM or email me, if you do...
Cargo Master
Joined: Nov 2015
Posts: 3,366
Likes: 915
From: Fort Worth, TX
Thread Starter
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Hotshot
Joined: Dec 2014
Posts: 17,762
Likes: 3,053
From: Jersey Shore
Chris,
If a person has no additional layover cable between the batteries, only the stock cable, moving the body ground from the passenger battery to the driver's battery can improve the voltage to the PCM and FICM. Now you are taking both the positive and negative for those controls from the driver's battery, which is somewhat constrained by the factory cable between the batteries when the starter is engaged.
I don't think this is any different than what I said in that older post.
If a person has no additional layover cable between the batteries, only the stock cable, moving the body ground from the passenger battery to the driver's battery can improve the voltage to the PCM and FICM. Now you are taking both the positive and negative for those controls from the driver's battery, which is somewhat constrained by the factory cable between the batteries when the starter is engaged.
I don't think this is any different than what I said in that older post.
Trailering
Joined: Oct 2010
Posts: 18
Likes: 1
From: Olathe
Bonding Cable question
Do I need a bonding cable or can I use a regular ground cable at the Frame to body location. My bonding cable was rotted away and I think....it maybe related to my intermittent stalling even after doing the pigtail on cam sensor still had intermittent stalling. NO CODES!!
Thread Starter
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Hotshot
Joined: Dec 2014
Posts: 17,762
Likes: 3,053
From: Jersey Shore
You can use a standard twelve-gauge cable. The braided one is theoretically ideal for high-frequency interference, but no one who has replaced them with a standard multi-strand wire has ever reported an issue, and I never noticed a problem either.
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