whew..............I took the time to read through your entiiiiiiiiiire post. It would make much easier reading and you will get more responses if you make it more "Reader Friendly". Break it down into short paragraphs would help a lot.

That said, it sounds as if you have an intermittent grounding issue. Im guessing you live where they salt the roads? Even if you don't there can be corrosion develop and cause these issues.

They are not easy to locate and I can't tell you even where they are all located, but the issues are too wide ranging and all seem to be electrical supply so the only thing they share in common are grounds.

Sometimes the corrosion is not even visible to the eye, lying under the ground strap so you should remove each, clean with a brush and reattach, with Di-electric grease in between to minimize the possibility of the corrosion returning.

 

Thanks for the feedback. I cannot edit the post but I was hoping each issue would format differently but it makes it hard to read. I apologize but I hate reading pages of forums because the OP does not include details that have to be squeezed out through further questioning. I wanted a thorough explaination in the first post to help give an accurate description on what I am facing.

I am having difficulty finding the chassis grounding locations online. Is there a good place to find all the grounding points on the LMM?

 

First, go to the bottom of yoru original post. There is a black button called "EDIT" click on that and a box will pop up where you can edit it and then "Save" it afterwards.

Second, do a search for LMM ground locations.

 

No Edit button. My only choices are to "quote" and "quick reply"

My searches are not showing a comprehensive LMM wiring diagram or posts that clearly define where they are located for the LMM. Most posts I am finding are guesses. A logical wiring diagram would be most helpful.

Update: I have removed the 2 grounds where the battery ground attaches to the chassis. Ring terminal connections to the chassis were clean but I used Emory cloth and cleaned all terminals and bolts so they were bright and shiny and reattached to the metal chassis with dielectric grease. There still is a problem with the interior lighting dimming and radio cutting out.

I need to find the other grounding locations for the chassis, especially for the interior cluster and accessories.

 

I don't know for sure as I don't have one, but I remember a post where someone said there was a ground lug for the interior stuff in the cab by passenger door.

 

Free wiring diagrams here: BBB Industries- Premium Alternators, Starters, Power Steering Products | TSB's & Wiring Diagrams
Make sure you select wiring diagrams or you will get TSB's


Do you live in an area that gets lots of salt on the roads? Check battery to engine block cable attachments at the engine, and the engine to chassis ground strap (near the starter, I believe). You could run an additional wire from one of the battery grounds, to the engine, to the frame, to the chassis and see if your problems go away. If they do, you have a good lead to what the problem is.

 

Ground Locations Thread LInk

Did a search for "Body Ground Locations" on here, this was the first thread that came up. This guy put some research into it.

I hope this helps you.

https://www.duramaxforum.com/forum/2001-2007-gmt800-non-powertrain/369330-ground-points-obs.html

Besides a ground issue it could be a shorted wire or wires in one of the wire bundles. There are many threads on here detailing this issue as well.

As the vehicles age time and heat deteriorate the wire loom surrounding the wires and they chafe, causing a short.

These are more difficult and time consuming to locate 'Im afraid.

 

Did a search for "Body Ground Locations" on here, this was the first thread that came up. This guy put some research into it.

I hope this helps you.

https://www.duramaxforum.com/forum/2001-2007-gmt800-non-powertrain/369330-ground-points-obs.html

Besides a ground issue it could be a shorted wire or wires in one of the wire bundles. There are many threads on here detailing this issue as well.

As the vehicles age time and heat deteriorate the wire loom surrounding the wires and they chafe, causing a short.

These are more difficult and time consuming to locate 'Im afraid.

Thanks for the info. I am doing my best to trace these down. I found lots of threads about ground locations, but none specifically described the LMM ground locations. I have pulled back the plastic trim by the dash on both sides and do not see any bolts that have a ground wire stud mounted to it so far.

I would not be surprised if there was a short because all the plastic conduit under the hood has broken away (there is very little left and touching what is remaining will cause it to break apart). Engineers can build space shuttles that last repeated trips to space over a 30 year timespan but cant design a wire bundle to withstand known temperatures in the engine compartment for 10 years...

 

Update: I found another ground under the driver's door but it appears to be for the trailer brake controller and the 4 wheel drive controller. As soon as I disconnected it, the DIC went nuts on those two items. I cleaned those contacts (they were pretty dirty) and reattached using dielectric grease to keep the contacts from corroding again. Sidenote: I hope this fixes my "service trailer brake" issue that I have been wrestling with for some time now.

I also found a braided ground strap that attaches to the firewall under the hood on the driver's side. That was fairly clean and tight but I cleaned and reattached it as well as a precaution. The other side of the braided strap could not be seen, so I could only feel the attachment and check it for tightness (which it was).

I am still searching for the grounding point for the dashboard and radio cluster. There are no grounding straps or lugs in the front door area or main dashboard attachments on either side of the dashboard. I have done a pretty thorough search under the driver's side but have not located any thick black wire (I am looking for at least a #14 gauge black wire).

The documentation linked by Ron was really helpful to map out the different components that bond to a particular grounding point but it does not show where those grounding points are located. I think I need to find G301 grounding point according to that documentation.

 

Here you go: View attachment G301.pdf

 

Here you go: View attachment 1027825

Thanks Ron. I have spent the morning looking for these grounding points but could not locate some of them and the ones I found dont seem to correspond with the grounding diagrams I printed out a few days ago.

G301 was clean & tight (it did not cover the radio or center console because everything stayed on when I removed this wire) It appears this wire is for the passenger power seat. It was only a #14 or #16 gauge cable
G303 was clean & tight on both the passenger and driver side and they only seemed to cover the rear power windows and automatic door locks for their corresponding side. Each side had 3 #14 or #16 gauge cables attached to a washer and attached to the chassis using a screw.

I could not locate G304 or G302 which makes me think this particular diagram you attached is not for the 2500 Diesel (Is the 2500HD considered a light duty truck?) I have pulled away the carpet as much as I could to confirm that the grounding points do not exist.

I have jiggled every wire bundle that I could find in the interior and cannot get it to short out or replicate the issue I am seeing when driving.

 

Have you checked the large wire bundle and connectors located above the engine on the drivers side of the resonator box.

I just looked at mine and the upper wire loom seems to be resting on the edge of the handle for the lower connector. I am going to wrap mine as soon as I get a day free to do so. It appears to me the edge of that disconnect handle could easily pierce the loom and eventually wear through the insulation on the wires inside, shorting them.

I don't know what all is connected by those connectors but I dont wish to find out by having electrical problems either.

Perhaps someone with more knowledge of these engines than I have can tell you what all those connectors feed.

 

I think this has to be a ground issue because if there was a short on the positive side of the circuit, I would be popping fuses pretty regularly. I have not had any fuses blow, so this has to be a ground issue but finding all the grounds is not easy work. I wish there was an easier way to check all the grounds. The interior grounds are under the carpet and I actually had to cut back portions under the seat to get to the grounding lugs but that instrument cluster grounding lug has been very elusive.

I did eject and reseat the main fuse cluster under the hood (driver's side) hoping a loose or dirty connection could be the culprit, but I am still seeing the issues.

This truck has been amazingly reliable for years until it turned 140k this summer and now it is possessed by a gremlin. I have performed regular maintenance on it without fail to keep it reliable. I was thinking of keeping this truck for a few more years but I might have to accelerate replacement because I do not want my wife to be towing her horse and trailer with an unreliable truck.

 

The information I posted came from GMUPFITTER.COM and is for 2008 light trucks, like 2500HD or a 3500HD. I looked at the wiring diagram from 2 other sources and that matches also, radio is grounded by G301. 6-way power seat (passenger) is grounded at G304. G304 appears to be a the passenger side pillar. But that doesn't mean much if your truck is different for any reason. Sorry I couldn't be of more help.

 

I appreciate your help on the matter. It is pretty obvious that this is not an easy find. Would you happen to see if there is any documentation for the grounds under the hood to make sure I got them all?

 

Ther're available at : https://www.gmupfitter.com/pdflists/view/6
Make sure you select the electrical section to get grounds and wiring. Lots of information available at this site.

 

I recently had a similar but not as bad experience with my 2007 NBS LMM.
Interior lights flickering and made worse by toggling the high beams on. Throwing nonsensical ECM codes as well.
Long story short it was the alternator. Like in your case it was charging according to the OEM dash voltmeter.
It hasn't been very long since the alternator swap but since it was swapped all of these issues are now gone.
These trucks are known for parasitic draw issues which will kill good batteries after the trucks sits for more than 4-5 days.
The diode(s) go bad in the alternator but it will still charge
Mine had a bad parasitic draw that got much worse over time. It blew the meter fuse as it passed 20 amps so the draw was greater than 20 amps.
Good luck... there is no larger nightmare for a mechanic than intermittent electrical issues.

 

I am going replace the alternator as my next step if the problems come up again (the gremlins only come out a few times a month).

Over the past few days, I have discovered a few things:
-In trying to find the Radio/Dash ground (which I cannot find still), I also stumbled across a few other small grounds that were under the hood and were pretty dirty.
-I was going over wiring diagrams to the point of nausea when it dawned on me that the positive bus bar could be the problem. This is the main distribution from the batteries with 125 and 175 amp fuses on the firewall next to the passenger battery. I removed all fuses and terminals and gave them all a good cleaning because they were pretty dirty. All connections were already tight, so it wasnt a loose cable but it didnt hurt to inspect and clean it. Who knows if that could be the issue (time will tell)?

If anyone has information on the Dashboard/Radio ground location, I would be thrilled to find and clean that one.

 

Quick Update: The issue has not come back so far ever since I cleaned the electrical contacts on the positive distribution box (where the 125 & 175 amp fuses are) against the firewall on the passenger side near the passenger battery.

I am not 100% sure I solved the issue but it has not come back in 2 weeks and I have completed a 3 hour wet road trip this past weekend (this is a good sign). For those trying to chase down this same issue, I wish you good luck and patience.

I will update the thread if anything happens.

 

I will update the thread if anything happens.

Well... It happened again after a 6 week hiatus. I took it directly to my mechanic and showed him in person. He stated the charge voltage was "a little low than he would like to see" but it was constant, so he did not think the alternator was the issue.

He witnessed the lights flickering and radio popping all while showing well over 13 volts from the battery terminals. He agreed that it appeared to affect the entire electrical system (meaning it was not a individual circuit or ground wire). He could offer no suggestion on what to check for next and had noone to refer me to other than take it to a GM dealer but also to "be prepared to spend thousands for them to guess".

I am at my wit's end on this because the engine stalls sometimes when this happens. I cannot let my wife tow a horse trailer with horses on the interstate with this intermittent problem coming and going. I could not live with myself if this happened to her and she gets into a collision because she lost control due to the engine stopping.

Any suggestions?

 

Declare victory. Invite your friends over to look at your great work. Give expert advice to others. Have a beer or two!

 

So I took it to the dealership this morning for the airbag recall and had them run a diagnostic because I need another opinion at this point.

They reported the alternator as being weak. They said they could only get it to generate 50 amps maximum out of the rated 125A. It is a no brainer then to replace it but I am going to do it myself with an AC Delco 28817848 OEM part.

Now for the bad news they delivered to me. They essentially want to replace all wire harnesses under the hood. They stated to me that most of the larger gauge cables have about 2.5x the resistance that they should have. I will say that the front battery cable is a little swollen close to the battery terminal connector but the other cables appear to be ok in my eye. It will be over $2k for parts and labor to replace the cables with no real guarantee that it will fix the problem. I politely declined the battery cable replacement and want to see how the alternator change goes for the time being.

Has anyone replaced the main positive battery cable from the front battery to the rear battery (and then to the main positive bus bar before the 175 Amp fuses)? I think it is one really long cable with two battery clamps and a ring terminal on it. I am trying to find the part number (or a diagram) for the LMM so I can start to look at maybe doing this cable replacement during the holidays.

 

Has anyone replaced the main positive battery cable from the front battery to the rear battery (and then to the main positive bus bar before the 175 Amp fuses)? I think it is one really long cable with two battery clamps and a ring terminal on it. I am trying to find the part number (or a diagram) for the LMM so I can start to look at maybe doing this cable replacement during the holidays.

After posting this, i realize that the LMM wiring harness under the hood is all in one, so you cannot easily replace a single cable as they are all bundled together. So never mind on that one.
source:

My plan of attack currently is:
1. Replace the alternator ASAP
2. Recrimp the battery cables with new battery terminals by cutting the old corrosion points out and getting to fresh copper wire (Military-Spec-Battery-Terminal-Post Kit)
3. if above two do not fix it, replace wire harness as a last resort.

My current wire harness plastic conduit under the hood has cracked away where I have exposed wiring everywhere, so doing #3 might have a silver lining in that it might prevent future issues as the existing wiring continues to break down from the heat and weather exposure under the hood.

I welcome any input you may have.
Thanks,
Chris

 

If your battery cable is bad maybe the alternator is ok, it just can't push more than 50 amps through a bad cable.

 

I went ahead and replaced the Alt today. One thing I did notice was that it took much less time for the dash voltage meter to go from 12 to 14 volts after starting the truck. The old alternator would take about 20-30 seconds after starting to get to 14 but after the new alternator it only took about 8 seconds. I know it may have been unnecessary, but I have a big trip this weekend and I would rather spend a few hundred replacing an original part (that has 140k miles on it) that likely would go out sooner or later. IF the problem returns, then I know it is not the Alternator.

I did do some more voltage testing after the alternator install and found a 1v drop in the ground cable between the rear battery and the chassis. I traced the wire to the block and confirmed it was clean, but a smaller wire that I missed during my initial troubleshooting went from the battery terminal to the front bumper and it was very very dirty and rusty. I cleaned that and found another ground on the other side that wasnt as bad but that got cleaned as well.

After cleaning those 2 chassis grounds, I got about 220mV of voltage drop on that same battery terminal, so considerable improvement. I think I have done all the testing that I can for now but I cant find a connection that has more than 300mV of voltage drop in my main distribution cables(from what I have been reading anything above 400mV is concerning).

This is a "wait and see" situation, so I will report back if there is anything to report. I will also try to create a thread referencing all of the grounds and their locations for any poor soul that needs to do the work that I had to do.

 

Surprise, surprise. I would have never thought to look at that cable, and I was also surprised to see that the fuse box was fed by a cable from the mega fuse (on the passenger side) around the back of the engine over to the fuse box, almost to the driver's side battery. I always assumed that the fuse box was fed by the driver's side battery. Use some Deoxit D5 spray to assure good electrical connection. Surprising how good this stuff is. The posted wiring video was great. Hard to get that view when everything is attached to the engine and transmission. There have been several people with various kinds of electrical problems that may be solved by your explanations, persistence in locating your problem, and detailed look at your truck's wiring and charging system.


You reported that the dealership said you had excessive resistance in the main battery cables. Do you recall what an acceptable reading was or what your reading was?


I believe the part # for the long battery cable (driver's side) you mentioned in your 1st 10/30 message is 25886568, about $350 at full dealer price. Few listings, some say part # is discontinued.

 

Yes, the normal value they said was about 200-300mV drop is ok but anything above that is concerning. In my case I have a 1.1 volt drop between the front positive battery terminal and the back positive battery terminal (the only thing between those cables is the starter). The starter is fairly inaccessible, so i cant get a reading between each section of the battery terminals but I think a bulk of the resistance is the swollen and corroded cable right next to the front battery terminal. I plan to cut back the cable to fresh copper (I should have cable slack) and put on a fresh lug with some dielectric grease and crimp that with a hydraulic battery crimper that my father in law owns (https://www.harborfreight.com/hydraulic-wire-crimping-tool-66150.html. Even though I dont think this is the cause of the problems I have been having, it is still important to fix this.

I have not measured the volt drop between the main fuse block on the passenger side and the main fuse panel on the driver's side but because this issue is intermittent, I fully expect a normal value but if the problem happens again, I will check the volt drop from 30 amp stud since that passes through the fuse panel. I am betting when this issue happens, i have a severe enough volt drop due to a dirty connection and that causes my ECM relays to open for a split second and that is what causes my engine to lurch off. All other interior and exterior symptoms would back that theory up (dimming lights and electronic undervolt cutouts, etc) happening at the same time. I think it is logical to assume it was the alternator conking out because it would cause a major change in voltage but now that it is replaced, we are seeing the same thing. I still think chainging the alternator was a good idea (it was looking a bit rough).

I will keep y'all posted.

 

Chris

Great news and I'm so glad you posted your voltage drop readings. Just today, South Main Auto posted a very good, though basic, look at 'how to' voltage drop investigation. Near the end there is a blank place for several seconds, and then he showed how you could use a digital temp gun to detect hot wires and thus problem areas. This lines up very well with the work you've done and so faithfully documented for the rest of us.

Here is the link to the video:

I note that tat the end of his videos, Eric O says" If I can do it, you can do it ". You just need a little knowledge and a video to show you the way. Great direction for all of us who work on our own trucks.

I look forward to your final (I hope) report outlining all that you've done to solve this problem.

 

Chris

Great news and I'm so glad you posted your voltage drop readings. Just today, South Main Auto posted a very good, though basic, look at 'how to' voltage drop investigation. Near the end there is a blank place for several seconds, and then he showed how you could use a digital temp gun to detect hot wires and thus problem areas. This lines up very well with the work you've done and so faithfully documented for the rest of us.

Here is the link to the video: https://www.youtube.com/watch?v=3xjLtg3FLoA&t=0s
I note that tat the end of his videos, Eric O says" If I can do it, you can do it ". You just need a little knowledge and a video to show you the way. Great direction for all of us who work on our own trucks.

I look forward to your final (I hope) report outlining all that you've done to solve this problem.

Great video detailing how to properly troubleshoot these electrical problems. Sometimes they are right in front of us and other times it can take days to find it.
A lot of us take the hit and miss approach jumping from one section to another without fully checking out the section we started in.
One must adopt a methodical well thought out approach using the right test gear to have any hope of finding hard to find electrical problems.
I have had the pleasure of watching emergency call in electrical techs do their work when I was an industrial tech.
These guys make it look simple. They assume nothing in a circuit until they test it themselves. Using a step by step methodical approach it is just a matter of time until they locate the problem.
I watched what they did and none of it was beyond my skills... other than I didn't know the correct procedures they used everyday. They start testing at A then B then C... testing every connection and device in a circuit until they find the problem.

So, Great news so far. On Tuesday, I started my work. I had to cut back the positive wire of the front battery a full 6 inches due to corrosion creeping down from the battery terminal. I cut it back until I had fully clean copper. Due to not having enough positive battery cable to reach the front battery anymore, I had to extend it using a 12 inch marine grade 2GA battery cable (I cut the lug on one end and crimped a 2 ga butt splice with dielectric grease on both cables, followed by a 6 inch piece of marine grade heat shrink tubing to ensure a weather tight fit). All crimped connectgis used a hydraulic 10 ton crimper specifically made to crimp battery lugs. I also cut back and replaced the negative lug of the back battery because that was also hot to the touch during my electrical issues. The last thing I did was remove the fuse block and cleaned the quick connect fitting and gently bent the metal to make sure it made better contact with the blade on the fuse block. I then liberally applied dielectric grease into the receiver of that quick connect fitting and connected everything back together. All crimped connections were sealed with marine grade heat shrink tubing with a heat activated adhesive to ensure a weather tight seal.

Voltage Drop Before recrimping battery cables:
Positive battery terminal between front battery and back battery - 1,220 mV drop
30 Amp stud on main fuse block to front battery positive - 1310 mV drop
Back battery positive to 30 amp stud on main fuse block - 720mV
Back battery negative to top engine block (near alternator)- 510mV

Voltage Drop After:
Positive battery terminals between front battery and back battery - 45 mV drop (1175mV improvement)
30 Amp stud on main fuse block to front battery positive - 55 mV drop (1255 mV improvement)
Back battery positive to 30 amp stud on main fuse block - 32 mV (688 mV improvement)
Back battery negative to top engine block (near alternator)- 22mV (488 mV improvement)

I was gone from Wednesday to Sunday, so I only was able to briefly test out the truck so far but it has been good so far. One other thing I noticed is that it has a really strong start now (it sounds MUCH better when starting).

I will update if anything comes up. After the new year, if it has not reappeared, I will declare victory and write up a summary of what I did in case other people have the same problem and find this thread. Thank you all for the help. This has not been easy, but I have learned a lot.

Not to jinx you but it seems you found your demon. Even if you didn't the repair work you have detailed needed to be done.
Typically I'm not a fan of splicing heavy amp load circuits. I have done it in the past using a very similar method you used. The way you made the splices is not going to cause you any trouble over the life of the system.
I have seen some very bad splices on these heavy circuits thinking some people are dangerous with tools in their hands.
You have done a lot of work trying to pin this down AND have taken the time to detail the work so as to benefit others who may have the same issues later on.
Thanks for taking the extra time.

 

First off, I posted this to 911 forum because I do not consider the truck as safe to drive on the highway or congested streets, but for some reason it does not show up on that forum. I am posting to this thread hoping it will post (since it will likely be moved to this thread anyways).

I have been battling an intermittent major electrical issue for a few months now and it seems to be getting worse. I purchased this truck from my brother a few years back and it has been a great truck up until recently. Let me try to break down the issues chronologically. I am not sure if these items are related but I wanted to mention them.

-Starting off- Around May 2018, I started to get "Service Trailer Brake System" on the DIC. I have been reading DM forums for a solution but the most common replaced part did not fix the issue (ACDelco 20904439 Trailer Brake Controller Module). This still happens from time to time mainly sitting at a red light during brake pedal movement (usually when brake is released) , which makes me think it is the brake pedal sensor as more time passes. I have not had time to have that changed out yet.
-Over summer I noticed that I was getting intermittent hard starts (cranking sounds weak, like using a weak battery). I had both 1 year old AGM batteries tested individually (they passed with flying colors), so I cleaned the terminals and put a fresh helping of battery terminal grease on the terminals. The issue never really got better but the truck never had a problem not starting at all. Some starts are amazing, more starts are just ok.

• Early August - Every once and a while the radio would reset the clock to 12:00, indicating to me that it lost enough power to reset the clock. This usually happened when I started the truck.
• August 14th - Local mechanic does an overall inspection and fluid service since truck turned 140k miles (changed brake, transmission & transfer case fluids at my request; replaced rear brakes & rotors; inspected belts & hoses; I asked him to look at alternator and batteries because of clock reset & harder starts - no issues found). I DIY the fuel filter change because it is super easy to do and I have done 2 others with no issues at all.

-Labor Day Weekend - While travelling back home at night on the interstate a few hours from home. The radio starts to crackle and the dash lights start flickering along with the headlights. This is especially noticeable when activating high beams or turning on a turn signal. I suspect it is the alternator, however during this fit of random flickering the dashboard shows 14+ voltage the entire time. I make it home on a wing and a prayer and take to my reliable mechanic after the holiday. His electrical guy spent 5 hours looking at everything and said that they could not find any issues. Since this issue is very intermittent, we could not replicate it. He felt bad that he couldnt find anything that he didnt charge me. It was fine for a few weeks until my next out of town trip (mentioned below).

• September 10th - "Water in Fuel -Service Required" - I just recently replaced my Fuel Filter myself a month earlier (1.5k miles ago). I read on this forum how to look into this error. I bled the filter and removed the sensor to find it was stuck in the up position. The fuel in the filter was captured in a mason jar and no water could be found. I put back together and I have seen the warning 2x since Sept 10th but they clear after the next start. Because I did a water inspection, I was not worried about water in the fuel. The problem has not appeared since Sept. 19th. I only mention this because I am wondering if an electrical issue could be causing this false positive.
• September 23rd @10am - I went out of town on the 21st and the 100 mile trek was fine. During the 21st, I pulled a 8k pound trailer and did at least a dozen start/stops of the engine and drove around short distances in the town I was in with no problem. September 23rd, I start up for the day around 10am to run an errand and within 2 minutes I had the worst episode so far. I was on a residential street and the radio goes dead for a few seconds (with loud pops over the speaker) and my dash lighting flickers. My accelerator pedal input was being ignored during this time, the engine was running but ramping down from about 3k RPM, (I still had power steering and brakes). About 2 seconds after this episode, I get power back and accelerator is responding again. I pull over to do an inspection and find nothing wrong. During this episode, I could see that the dash electrical meter was still above 14v the entire time. No other major issues to report during after that episode. I drive around the rest of the day with no issues (I made about 6 trips)

-September 23rd @ 8pm - I am travelling home from my weekend out of town on I-35 and get about 20 miles before I have another flickering episode. The dash lights start flickering with the headlights and the radio starts to crackle and the speakers start to pop as if the radio is losing power (like a voltage drop), but the voltage meter on the dash is reporting slightly above 14 volts. I swear I smell a burning smell, so I pull over at the next available exit to do another inspection under the hood and elsewhere. No burning smell and no evidence of any electrical fire. I have my hazards, headlights and dome lights on and I notice that the domes, headlights, and dash dim significantly when the hazards illuminate. I have a video of it that I will try to upload to youtube shortly. I take a voltage reading using a VOM and show it is reporting 14.55 volts at the actual battery terminals but showing regular dips down to 14.2 volts regularly (i assume because of the incandescent hazards). I decide to drive on the deserted interstate service road for a few miles to a rest stop a few miles away. During this time, everything was fine. After doing some more inspections, I decided to get back on the road. For the next 70 miles, there was not a single issue but as I got close to home, I had the flickering and radio problems again (not as bad as before but still happening). I get home and cannot replicate the issue.

So given all that, I want to get another inspection done but I want to walk in prepared to discuss the recent events to my mechanic to help narrow down the problem. I do not consider the truck safe and I will not let my wife pull her horse trailer with it until further notice. I am especially fearful of a complete electrical failure at highway speeds, which would cause engine to stop, power steering and brakes to fail as well. This scenario has not happened yet, but I feel that events have gotten progressively worse (especially with the loss of engine acceleration during the Sunday Morning episode).

The symptom seems to be fairly consistent when it happens: The entire truck components appears to have a severe voltage drop across all systems at random times even though electrical meters confirm the batteries have 14+ volts when the engine runs. These issues appear to come and go more often while the truck is in motion, however there are days/weeks that I have driven without any symptoms at all (I live in Dallas and we have some rough streets and that does not seem to jiggle anything loose).

Does anyone have any suggestions. I would greatly appreciate any and all suggestions.

 

I’ve had the same issue get a piece of four gauge grounding wire and mount it to a bolt on the motor in one of the body grounds inside the engine bay and see if it helps that’s what helped my truck

 

Hello - I understand this is an old thread so apologize but I had a similar issue with a different solution.

TLDR - one of my battery + terminals was loose.

I was making a 6 hour drive home driving an '08 C5500 Jayco Seneca towing a trailer. I started having issues with my electrical power cutting out - all of it. Headlights, cameras, dash, but it would immediately come back on a second or two later. Then the truck went into limp mode and would not start, seemed to have very low voltage. Disconnected battery (-) terminal on the side of the road and the truck started back up.

I drove 150 more miles home with a CEL and WIF light on. When I got home, I decided to remove all battery cables in case something was shorting and might cause a fire. The positive terminal was "a strong finger tight". Definitely on there but not super tight. This was on the rearward battery with both battery cables intersecting. The front battery has only one cable.

The next day I found that I could get the truck to lose all power just by wiggling that terminal slightly.

If anyone is having a similar issue, check your battery connections to make sure they are TIGHT (properly torqued). Finger tight is enough to shut things down.