This is just quick preliminary work checking on the current flows for the three body ground cables. These are the pathways for either battery or alternator current, depending on wait-to-start, cranking, or running conditions. It's half the equation on how the PCM, FICM, and all other electronics are fed.

My truck had two 8ga cables replacing the stock cable frame to body years ago. A stock cable is on its way to me from TN to reconfigure back to stock, so the current flows will be different stock. Scott (diesel_dan) ran a check for me to confirm these values are not stock.

I have probably 12 more morning checks in front of me to confirm stock and a couple of alternate choices to see if there can be a better way or the stock layout is fine.

You guys clean those cable connections under the truck don't you?

 

So let me get this straight? That little POS ground cable right under the passanger door flows 15 amps? Mines about to fall apart I guess I need to get on that...

 

It does on my truck, but I've got two 8ga wires there. Scott was kind enough during his hectic weekend to check his and got 9 to 10 amps, peaking higher at start. I've got a stock cable coming to me so I can get a true baseline.

During post start conditions the positive cable from the drivers battery to junction box of all electronics pulls 18-20a until you start using accessories. So yeah, that cable neglected by many and usually bolted in a corroded condition contributes a significant amount of current to our FICM and PCM. More if you've added a cable like I did 5 years ago. Mine was burned away when a dealer tech screwed up my passenger battery negative cable where it connects to the frame, the situation that started my journey on improving battery cables and grounds.

Anyway, after doing the battery cables this is the start of trying to find an improved way to get those pesky electrons to flow to the FICM and PCM in a more respectful way. With my background I have to test and confirm rather then just throw a cable somewhere. I've already been playing with alternatives as Scott knows, but I need to confirm tests under a few trials before I get ahead of myself in posting. But I thought showing this cable was important based on both my and Scott's readings before finding a better pathway.

Edit - and those are the current flows without any accessories on. If you have on lights, HVAC fan on high, etc there will be another 40-50a moving through these wires.

 

Thats a great post. I have a '59 car that I had gremlins on turned out to be grounds, but I never really thought about checking my truck grounds.

 

agreed, great post and really appreciate the detail and testing you go thru. i look forward to the conclusion so i may begin to address this in a proactive measure

 

This is another upgrade I'm looking forward to seeing if I need to make. Thanks Mr. Jack.

 

Rusty A in another thread posted about trying to improve his voltage pids, one of the two motivations for me. I'm still not finished playing around with this investigation but I thought I'd post the results of what I've got so far. Maybe most of you already have as good of a reading and I'm just fixing my own issue, but I thought I show my results.

My goal again is more stable voltage and balanced flow of the negative side to the positive side, which all leads to better voltage to the FICM. Right now this is maybe $15 of 8ga wire.

The vid is just a 4 min showing of the SG and power port voltage, so if you've got more important things to do .... The first half is after I started the vehicle on one of our early warm days, then the second half is the same day after a 45min drive to work at the farm then drive home, but I turn on all the electrical accessories in the truck. Headlights, A/C Full, radio, wipers high, heated seat, and brake lights. So this is full hot with the alternator voltage regulator lowering voltage for hot battery overcharge protection.

I'm also posting this to see if I'm finding a fix that nobody needs

 

The video is set to private.

 

Changed it.

Is this an improvement to what others see, or am I just improving my own truck?

 

Better electrical flow is ever a bad thing. I already have the cablig for the positive side upgrade but have ot installed it yet. I would upgrade the groud side as well, without question. Unfortunately I have to wait a few weeks as I am having back surgery next Monday.

I have not doe any formal testing but I do see a lower battery voltage after the truck is warm. I have also oticed that the FMP, FLP, Batt V and voltage read at the obd port are all different. I am assumig this is due to voltage drop from small wiring, corroded grounds and small power cables.

 

This is different then the previous work. The prior was really about getting both batteries to work together. This is about, at least my experience with my truck, it getting a better, more consistence voltage to the FICM and PCM.

Good luck with the back surgery Brian. I was diagnosed with needing that in my 20's but decided to go au natural so lived with 10 years of pain. But surgery back then was not as precise as it is today and I think my decision would be different.

 

Jack: this is with your new cable from Driver's Batt Neg --> FICM ---> PCM , correct? I have not done that yet.

I'm having some issues with Torque and data logging a file for you. What I am trying to capture is data of all voltages on cold start and for the first couple minutes. I somehow have barfed Torque so I am not getting any logging. Once I figure that out I'll get you that file.

I will also, based on what you are doing here, try a data log fully warmed up and turning everything on.

It has been hotter 'n hades out here, but might see a little cooling this week and I will try again. It is a case of going into Torque and changing just about every parameter I could to try and get the tightest resolution (quickest scan rate). I should have learned this lesson years ago: change one thing at a time or suffer what I am -- broke all logging I did...

 

Yep, along with cleaned ground/negative points while using NO-OX-IT conductive grease both under and over the connections.

Do you guys have stability like this? My truck voltages on SG would fluctuate more and show a higher differential to power port and battery before I did this.

Lesson I learned too, one change at a time.

 

Scott,

I've got so many vids with amp readings right now that you don't need to put yourself out getting any recording. Especially in heat.

 

Not a problem -- it won't be a video, it would be either an excel spreadsheet or comma delimited file with headers. It is so warm that the GPM is cutting off before you can sneeze, and I know if it is even just a bit cooler the GPM will stay on long enough to see the jump in voltage.

Post above that one of yours, answer is No -- that is something that caught my eye is how stable your voltages are, the 3 of them all seem to stay pretty stable compared to mine.

I will be capturing 3 different Batt voltages that all seem to read different and can bounce up to 9 10ths of a volt (just watching them), also FICM Main, Logic and Vehicle, which interestingly are much more stable...

But... Friends invited us to their pool and a BBQ, and my guess is there will be libations So doing some testing will have to wait a couple days...

I still am just at the extra battery interconnect and extra alt cable. So I can do a before and after. Since my truck is pretty pristine, do you think I should add the ground for the FICM/PCM before doing the frame rail ground? Or a particular order of doing these you'd like to see?

Keep up the good work!