Electrical gremlins

mike_osborn

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Guys

I have a 2015 Duramax 2500 that I want to use as a chase truck. I just had a bunch of suspension work done and a new Fab Fours front bumper put on. When I got the truck back, I have a bunch of sensor issues:

1. My airbag warning light on the dash is on.
2. My windshield washer fluid level shows as low - even though it's full
3. Every time I slow to a stop, I get a message about my park assist
4. The TPMS sensors on my rear tires are complaining. I think this is unrelated though.

I just installed an Edge CTS2 but there are no error codes.

My guess is that the shop that did the work either didn't connect a plug that combines these sensors or they didn't plug it all the way in.

Anyone have any ideas on where to hunt? Or is there another possible cause?

If not, any recommendations of a shop in Southern California area?

Thanks for any help!

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firedog

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Did the issues happen after susp/bumper work or after the you installed the edge?
 

green787

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You really need to unhook the battery (both terminals) when welding on the chassis.... Try disconnecting the battery (for 10 minutes) and resetting the computer.....
 

mike_osborn

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You really need to unhook the battery (both terminals) when welding on the chassis.... Try disconnecting the battery (for 10 minutes) and resetting the computer.....
I never thought about checking with the shop that did the work to make sure they unhooked the battery prior to welding.

I already tried disconnecting the battery. Left it disconnected for more than an hour.

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_

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You really need to unhook the battery (both terminals) when welding on the chassis....
Disconnecting the battery may be in-part important (never done this myself,) but disconnecting the Engine Control Unit, Body Controller, Transmission Controller and any other electronic controller/device is critical when welding. At anytime while welding, if there is not a constant, clean and direct path from the weld point to the welder GND clamp, it is possibly to fry circuits within these components if they are not completely disconnected and electrically isolated from the vehicle and all vehicle wiring.
 
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green787

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Disconnecting the battery may be in-part important (never done this myself,) but disconnecting the Engine Control Unit, Body Controller, Transmission Controller and any other electronic controller/device is critical when welding. At anytime while welding, if there is not a constant, clean and direct path from the weld point to the welder GND clamp, it is possibly to fry circuits within these components if they are not completely disconnected and electrically isolated from the vehicle and all vehicle wiring.
Disconnecting both positive and negative battery terminals allows no path for the current to go to these devices..
The electricity or current is not likely to back feed up the ground side of the devices unless like you said, you had the ground clamp far away from your welding area....
Even then, I can't see how it would damage anything...
If you brought a new or old truck, to me, I would disconnect both battery terminals and confidently weld a trailer hitch or roll cage to it without worrying about damaging the customer's electrical systems....
 

JDDurfey

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Disconnecting the battery is a good idea, but disconnecting the battery does you no good when welding if the electronic equipment is grounded to the engine block, frame, or cab. If this is the case and you do not want to run the risk of frying something you must disconnect any grounds and power to each component.

I weld on oil field equipment almost daily with Cummins engines. My Cummins engine's computer is grounded to the head of the engine by a cable and through the bolts, so in order to completely isolate it I would need to remove the computer completely. I never do this. I simply make sure I have a good ground as close to my weld as possible and so far I have never had a problem.
 

green787

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Ground is ground is ground.... With the positive and negative disconnected there is no path to these devices.... Try to consider how I ground the AC and DC to the same chassis in my chase truck... Ground is ground....
 

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Green, I respectfully disagree with your argument. And, I hate to see someone potentially mislead so I’ll try to explain in support of my disagreement.

The problem is, even with disconnecting the battery from the vehicle/chassis ground and positive (which is is in fact only isolating the battery from the vehicle,) there are electrical components on the vehicle which remain directly or indirectly attached to the vehicle/chassis ground. And, there is not a zero resistance path between all components (ie; sensors, IC chips, board traces, resistors, capacitors, transistors, etc) and the vehicle/chassis ground. As we all know, electrons/electricity will take the path of least resistance. And, we also know the welder will create a substantial electrical arc between the electrode and the ground as the positive electrons search out welder ground. And, we know integrated circuits, sensors, etc are not designed to accept the excessive voltage and/or current levels which are created by the welder while attempting to weld and these components will suffer devastating failure if subjected to these voltages/current.

Now, if we have a compromised ground path between the positive electrode and the welder ground clamp, or even a gap between the two materials being welded together with only one of the two materials having the welder ground clamp attached, the electrons may take a more indirect path, yet a path of lesser resistance to reach ground. This ground may be welder ground and even AC ground/earth. This indirect path may in fact be through a (or several) sensor(s), a wire harness(s), integrated circuit(s), electric motor(s), basically any component(s) which will allow the positive electrons to reach ground (welder ground or AC ground,) with less resistance than what may appear to a shorter, more direct route by the welder operator. The electrons will jump a gap within an ECU, sensor, integrated circuit, wire harness, etc. as easily as they will jump the gap between the positive electrode and the welder ground. Basically, any component which is not fully and completely isolated from the vehicle chassis ground/welder ground, with a gap larger than the gap which the weld arc cannot jump, or provides a path of lesser resistance to ground than that of the welder's positive electrode and ground, is subject to possible damage if the electrical pass through the component in search of ground. Again, disconnecting the battery will only protect the battery. It will not protect any electrical component remaining on the vehicle which is in any way, direct/or indirect, attached to the vehicle/chassis ground.

Over my years, I have seen several electrical components fried from poor welding practices. I have even seen laptops and battery chargers which were attached to the vehicle while simultaneously plugged into AC power, fried from welding on a vehicle. In one case, I witnessed a laptop sitting on the frame of the vehicle which was not plugged into the vehicle but plugged into AC power, fried when someone tripped over the welder ground cable, tearing the ground clamp way from the chassis while someone was welding. The welder positive electrons passed through the outer plastic shell of the laptop as it sourced AC ground through the wall plug.

Thanks for entertaining my argument. :):):)
 
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So, what's the solution for this kid???
 

JDDurfey

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So, what's the solution for this kid???
My electronic technician here at work tells me that to ensure you do not have a problem each electronic component needs to be completely disconnected. Some components can simply be unplugged, but like I was saying with my Cummins engines, the ECM is grounded to the head by a ground strap, wiring harness, and the bolts, so I need to remove the ECM completely to disconnect it. So my E-tech tells me to just weld away, but with the ground clamp as close as possible and do my best to make sure it is a good ground. So far, I have not had any problems.
 
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So, should Mr. Osborn blame the welding shop?
 

green787

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I know a lot of you have a lot of experience, but you still don't understand electrical design....
You guys are saying there's a back door path through ground to your devices....
With the positive terminal on the battery disconnected there is no way to complete a circuit to burn anything out....
You're still not addressing the chase truck or a boat where we routinely mix AC ground with DC ground, and even shore power ground.... None of these situations are any different than welding on your vehicle...
The electrons will flow in direction indicated with blue arrows.....
You can take that drawing to the bank....
Know your basics....
Chasis Welding 001.jpg
 

_

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Green,
In your drawing, what is the potential path of of electrons if the frame has a full and complete crack separating the front half from the rear half (we will use a full frame as we are using your full frame drawing for reference) located between the ECU and the Trans PCM ground points, and you strike your arc on the back half of the chassis vs the front half of the chassis? The path of least resistance may very well be through the PCM Ground to the PCM, then through the +12V shared between the PCM and ECU, then through the ECU ground to the chassis, then on to the welder round clamp. This will fry at least one of these component mentiond.

-or-

What if rather than a full and complete crack in the frame, this location between the Trans PCM and the ECU has poor electrically continuity due to severely rusty/dirty (or possibly an anodized or heavily painted or heavily undercoated) mating surfaces, yet the GND points for the PCM and ECU are clean and intact. Again, the path of least resistance may once again be through these components. But, if these components were fully and completely isolated from any and all electrical continuity from the chassis and +12V wiring, the path of least resistance would be strictly through the chassis.

I'm not saying every time someone welds on a vehicle they are going to fry a component, i'm saying it is wise to take the greatest amount of precautions possible to insure the path of least resistance is between the electrode and the welder ground.
 

green787

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ProFORMANCE, your scenarios are interesting but still no cigar....If the truck was completely broke in half, and some wires were still hanging on, you may have a point......But
#1....Ground also has to do with mass.... The mass of the chassis is enough in comparison to the ground points in your computer to attract the electrons...They will find no escape there and will turn around and go to ground....What you guys call the "path of least resistance"... It's more like the path to the nearest mass..... This is how a condenser dissipates electrical current.....The electrons are tricked into thinking there is a ground at the end of a tin foil wrap mass.... Uh oh... no ground... so they turn around and go back... then they get tricked again over and over until the current is dissipated.... There is not enough mass in the ground points in your devices to worry about the electrons going there spuriously...
#2.... I also don't want my trailer hitch welder unhooking all my electronics.... That's just not practical, and I believe you could call your local trailer hitch welder and he would confirm that he only disconnects the battery.... I hope....
 
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green787

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JD.... Plug in an extension cord in your garage and put the end in a foam cup of clean water sitting on a wood work bench....... Wearing sturdy shoes and not touching anything else especially the wet concrete floor...Do not use two hands...... Now put your finger in the water gingerly and report back to me what happened.....
We will not let you work in the motion picture industry until you try the "extension cord in a cup of water" challenge... Right there at the water cooler.... It will give you a "hands on" understanding of what I'm talking about.....
We can't let you work on anything unsupervised until you learn the knowledge.... Once we ascertain that you have the basic knowledge we'll let you work on Ultra High Voltage at power generating stations and such.... Non believers remain apprentices until experience teaches them otherwise.....
Spraying water on high power lines from a helicopter is a good paying job.... So is underwater welding......
 

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mike_osborn

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Thanks for all the insight guys. I found a place to take it to for a diagnosis. Will update this thread in a few days with the outcome.

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_

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Green, I feel there is no benefit in continuing this discussion. So with that, I will simply agree to disagree at this point and allow readers to take from this thread what they wish. :D
 
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