Electrical Ground locations

Realism

Registered Member
Original poster
Nov 25, 2015
145
Idaho
While troubleshooting a bad ground I came across some scans of the service manual regarding electrical ground locations for our platform posted on another site. This includes both short and long wheel base, as well as both 4.2L and 5.3L.

Credit goes to Wex. http://forums.trailvoy.com/showpost.php?p=1019927&postcount=2

*Note that ground locations may have changed from early to late model years


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yazan

Registered Member
Jul 11, 2013
178
Very helpful topic and graphics.
It will help me in my problem.
And this what can happen if you have a bad ground
 
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I have had a similar issue as of lately. Since I bought used about 3 months ago. I have done alot of work on my 2004 gmc envoy,valve gasket, power steering pump, rack and pinion seal, air intake manifold, ect..... After I finished the valve cover gasket I put in a par of led blinkers in the front right and left. They ok for a a day or two then, they started flashing fast like a dying bulb. Now when I turn my left turn signal it stalls out. I checked the battery, alternator, got bulbs back in,, all fuses, cleaned 6 grounds, ect. Ithink it messed up a relay somewhere or I might have knocked something lose for pervious tasks. Either way Tomorrow thank you for you diagrams. You might have solved a problem. It's my only vehicle and im really cash poor at the moment. I wil reply soon with and update of my progress.
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,153
Tampa Bay Area
Welcome to GMT Nation...

There are a few other Threads that describe this very problem on GMTN, so I'm not sure if my reply belongs here or in a New Thread for the "GMT360 Stalls on Left Turn Signal Activation.." but since these EXCELLENT Repair Instructions DO involve Grounds... Here goes:


This excerpted Diagram from the above Link should be similar enough for ALL 2002-2009 Trailblazer, Envoy and Rainier SUVs to be relevant with trying to solve the problem:

What is the "Common Denominator"...? ALL Three Circuits Share the Ground at the Position G-107. As ALL Three Circuits are activated... when there is additional Resistance imposed on the Copper Ground Wire due to Green Corrosion (Copper Oxide), a Loose Fastener or Rusted Metal on the Steel Body or Frame or Engine Block, the Energy is then converted into HEAT due to the phenomena called "PTC" where the Strands of Copper Wire demonstrate a "Positive Thermal Co-Efficient". Sounds Pretty Fancy...Huh? All this means is that the Voltage on the Line is being converted into Thermal Energy.

In Plain English... The Wires will HEAT Up and the Voltage will DROP. If the left Turn Signal was Turned On at the same time this problem of having a Poor Ground at G-107 is present... with the Left Headlight also ON... the Voltage Drop can be enough to trip the Fuel Pump Relay and thus... No Fuel...and the Engine Dies. There may also be other evidence of this by observing that the Left Headlight "flutters" whenever the Left Turn Signal is also activated, remembering here that this places a higher demand for the flow of Electricity to head back to Ground and thus... ALL Three Circuits will suffer from a Severe Drop in Voltage.

2002GROUNDWIRES.jpg
 
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6716

Hobbyist
Jul 24, 2012
767
I'm cleaning/checking the grounds in the engine compartment right now, and my question is for like G102, 103, 105, where there is a bolt that fastens the ground plate ... what is grounding? Is it the plate to the body of the vehicle? Is it the plate to the washer to the head of the bolt to the bolt shaft to the threaded bit?
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,153
Tampa Bay Area
The definition of "Grounding" or "Earthing" comes from the need for ALL Positive Electrical Electron Flow to have a Common Return Path back to the Negative (-) Battery Terminal in a 12 Volt Direct Current System . Regardless of where you manage find any Electrical Ground (or MAKE one) ...as long as the connections along the way are either Welded Body Panels or soldered or bolted together...then the Flow of Electricity WILL always return to the Negative Battery Terminal with the least amount of resistance.

For example (from the Question you raised in your other related Thread) you could unfasten any of the GM OEM Factory Body Fasteners found under the rear seat and apply some Dialectic Grease and connect a Copper Eyelet that has been Hard Soldered to any length of Automotive Grade Wire (See the Amazon listings below). You will want to avoid drilling any New Holes in the Floorboard and installing Sheet metal Screws for this purpose. Select either Green or Black as your Wire Color choice as these are commonly associated with SOLID Wire Colors in most Ground Wiring Applications

As long as the surfaces of the Metal between the Body Frame or the Copper Fastener-Wire being used and the Copper Eyelet are all clean and free of Rust, Oil or Grease... You should be able to establish an excellent Ground Connection. In High Amperage Applications, it is especially important to ensure Good Solid Connections with Heavy Gauge Wire that prevents any Electrical Arcing. This is why using only Automotive Grade Electrical Wiring Bundles, properly Soldered together and then Heat Shrink Insulated at all Connections is the Safest Method to employ.

This is the kind of Gear that will ease your mind about any Safety and Security issues afterwards:


 
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mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,153
Tampa Bay Area
If the reason you've come here is because you have Questionable Grounds... Viewing this Premium (Free) Scanner Danner Class on Multi-Meter Basics ties DIRECTLY into whether or not you will be successful in your Diagnostic approach and How to Use your Digital Multi-Meter to its greatest advantage. I would recommend Downloading and saving THIS Video in your "Mechanic's Media Library"

Trust Me... Even if you THINK that you know ALL there is to know about your DMM , Ohmmeter and Voltimeter... and their relationships with Diagnosing Circuits and Grounds... THIS information and THESE instructions will actually SURPRISE and edify you. Paul Danner's examples will give you a much needed advance on and provide Better "Grounds" for your understanding of Automotive Electronic Circuit Diagnostics:

 
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mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,153
Tampa Bay Area
This Video from "Crazy Ivan" at Pine Hollow Automotive Diagnostics is a Case Study in a 2012 Chevrolet Captiva "No Start...Can't Remove The Key" issue involving a VERY unusual failure in the Battery & GROUNDS System that will be universally useful to us whenever facing any ordinary problems with Diagnosing any NO START Condition:

Helpful Tools... But NOT absolutely necessary after you learn what the VOP (Video Original Poster) actually does to SOLVE this issue...

(1) DMM (DVOM)
(2) Digital Low Amp Clamp
(3) Laptop Computer
(4) PICO-Scope (4 Channel)..but would recommend the much less expensive Hantek Model# 1008C 8 Channel Scope)
(5) 16 Pin DLC Break Out Box
(6) Handheld TOPDON Thermal IR Camera
(7) OBD2 Scanner

This is Important:

Automotive Electrical Systems can become DANGEROUS if their Integrity is INCOMPLETE. It may seem like "Checking Grounds" as an afterthought will become the general approach in most situations because these concepts just seem SO BASIC. But Watch and Learn just how BAD things can get if these "Principles of Electricity" go sideways ...and undiscovered... and STAY FOR THE BONUS FOOTAGE:


 
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Scrappy608

Registered Member
Dec 21, 2020
11
Wisconsin
Thanks everyone for your help I took to a dealership and it was a ground run from along the frame. The ground shorted out inside the wire casing itself. And again thank you everyone 🙏
Hey JD, what did they get you for that there? Curious as I may find myself going that route.
 

mrrsm

Lifetime VIP Donor
Oct 22, 2015
6,153
Tampa Bay Area
As my Participatory, (...Hopefully… Contributory) Thread Count at GMT Nation rolls quietly past 6,000 on this Tuesday, July 5th, 2022 ...I thought it would be worth spending this ‘Shiny, Symmetrical Little Coin’ in a worthwhile manner by memorializing the imagery of the redoubtable GM Class 2 SP-201 Splice Pack Ground Connector after getting one that came out of a Pontiac Vehicle via eBay.

I’ve created this discreet "Baker's Dozen" Photo-Play as an addition to the work done for us by @MAY03LT in the Linked Video… which is recorded for our Best Use as a Topical Thread by @Realism to help us remember its importance ...For as long as Grass is Green... And Skies are Blue... And The Good Earth... is STILL "Ground". :>)


Description:

Class 2 Ground Network Splice Connection Point
Cadmium Plated, Spring Steel Contact
Supports up to 12 Grounding Wires
Black Plastic Casement
12 Tang Gray Plastic Insert
10mm Flanged Hex Head M8 X 1.25 X 25mm Bolt
Held with a Trapped Fastener via Tang Washer
All Metal treated with Durable Cadmium Plating
Up to 12 (7) Strand-Solid Copper Wires inserted
Black Poly-Acrylic Insulation

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