Big Three Replace Factory Grounds?

[iamdub]

Okay... Switched ground to side post and same thing.

All the wiggling I've been doing at the battery boils down to those wires running over the computer box and moving it. I rerouted the smaller wire that comes from OEM battery cable and back to frame ground where it was. If I apply pressure to the computer box toward the battery it does the stuff. Let off and it goes back to normal.

Do I have a computer connection issue? Is this common?

Hopefully I'm on to something. Thank you.

You're certainly on to something! Sounds like you've narrowed it down to a bad connection in the harness snapped into the PCM. Try unplugging them then plugging them back in firmly. But, it could be a wire or wires that goes into the connectors that plug into the PCM. You could inspect them to see if any look to be pulled out or just try to push all of them into the plug to ensure they're fully seated. I don't know how much slack there is, but if you could unbolt the PCM and have enough slack in the harness to have it up where you could work with it, you could gently wiggle or tug each wire until you find the one(s) that cause issues when you do.

 

[Dakcbeast]

Getting ready to head out now. I saw on another forum a guy had exact same issues and what he called "mud" on the pins. Cleaned them and problems gone. I may not get any trouble after rerouting just because there won't be any pressure from the wires on the box anymore, but that won't solve my problem totally. Here I go with a 7mm..

 

[Dakcbeast]

Pulled pcm out and inspected everything. The wire bundle on one looked to have some corrosion between the wires but I didn't see any bare metal? Going for a spin.

 

[Dakcbeast]

Nothing. Longer drive needed. Last night it was pretty much a constant. Only change is unplugging and plugging back in pcm connectors and rerouting wires so no weight on pcm box.

 

[Rolexus]

Hi All, new to this particular post, but I’ve got some serious ‘grounding issues’, such as EBCM, and Service 4WD messages that I’ve been working on.

Can some one give me a quick summary about what exactly are the “Big 3 Replace Factory Grounds”? Thanks!

 

[iamdub]

Pulled pcm out and inspected everything. The wire bundle on one looked to have some corrosion between the wires but I didn't see any bare metal? Going for a spin.

This stuff is pricey, but good. Honestly, owning an older GM product almost requires you to have this or something like it. You're almost guaranteed to have some gremlins from loose and corroded connections (PCM, window switches, etc.) eventually:

 

[iamdub]

Hi All, new to this particular post, but I’ve got some serious ‘grounding issues’, such as EBCM, and Service 4WD messages that I’ve been working on.

Can some one give me a quick summary about what exactly are the “Big 3 Replace Factory Grounds”? Thanks!

The "Big Three" are the three main circuits in a car's electrical system- Battery positive-to-alternator, battery negative-to-engine and engine-to-frame. Manufacturers use the bare minimum (if even that!) wire gauge to minimize costs, sacrificing some robustness of the electrical system. Upgrading the wire gauge and quality ensures all circuits supported by these circuits are getting the full amount of available power.

I think that it should be more of a "Big Five", adding body-to-frame (or engine) and battery positive-to-starter circuits. The body should be well-grounded since there are components inside that are grounded to the body. The starter is the biggest load on the system, so it makes sense to upgrade that while you're at it. Yes, it's only operated for a moment. But, allowing it to have all the amperage it wants will reduce the strain on the starter motor, making it stronger and extending its life.

 

[Rolexus]

Thank you for that explanation “iamdub” (sorry I misspelled your name earlier ), I will attack these 5 areas first, then eliminate the localized issues if still there.

The one I’m worried about is Service 4WD (have heard of people getting stuck in 4WH or 4WL). I’ve cleaned the frame mount grounds. I’ve found the small 4 pin connection on inner drivers fender, cleaned the 4 pin sockets, added dielectric grease and grounded the black negative wire to the firewall ground.

This was good for a week, then display came back. It has to be electrical - when the dash switch for AWD, 2WD, 4WH and 4WL are lite and functional, I can switch back and forth - no problemo!

After the above advice I should check transfer case control module and transfer case motor - plug-in sockets and ground wires.

Your thoughts?

 

[Dakcbeast]

Been driving around as stupid and foolishly as I can for the past hour and nothing yet. If only..

 

[Dakcbeast]

A few shorts drives today and nothing.

 

[iamdub]

Thank you for that explanation “iamdub” (sorry I misspelled your name earlier ), I will attack these 5 areas first, then eliminate the localized issues if still there.

The one I’m worried about is Service 4WD (have heard of people getting stuck in 4WH or 4WL). I’ve cleaned the frame mount grounds. I’ve found the small 4 pin connection on inner drivers fender, cleaned the 4 pin sockets, added dielectric grease and grounded the black negative wire to the firewall ground.

This was good for a week, then display came back. It has to be electrical - when the dash switch for AWD, 2WD, 4WH and 4WL are lite and functional, I can switch back and forth - no problemo!

After the above advice I should check transfer case control module and transfer case motor - plug-in sockets and ground wires.

Your thoughts?

Honestly, I'm not very well-versed on the 4WD systems. The only 4WD vehicle I've ever owned was an XJ and I've never worked on a GM 4WD system other than replacing axles and hubs.

From browsing this forum over the years, I know the module (Might be properly known as "encoder" or "encoder motor") is a somewhat common failure point.

 

[George B]

Thank you for that explanation “iamdub” (sorry I misspelled your name earlier ), I will attack these 5 areas first, then eliminate the localized issues if still there.

The one I’m worried about is Service 4WD (have heard of people getting stuck in 4WH or 4WL). I’ve cleaned the frame mount grounds. I’ve found the small 4 pin connection on inner drivers fender, cleaned the 4 pin sockets, added dielectric grease and grounded the black negative wire to the firewall ground.

This was good for a week, then display came back. It has to be electrical - when the dash switch for AWD, 2WD, 4WH and 4WL are lite and functional, I can switch back and forth - no problemo!

After the above advice I should check transfer case control module and transfer case motor - plug-in sockets and ground wires.

Your thoughts?

You really need to know what trouble codes it is storing for the issue before you can go much further. You were right to start with the grounds but now you need to know what component or circuit is malfunctioning. You should start another thread about it.

 

[Rolexus]

Thanks George, I was trying to deal with some of the more obvious sources of the problem in the simplest ways first, prior to taking the truck into a shop for a scan

 

[Rolexus]

Honestly, I'm not very well-versed on the 4WD systems. The only 4WD vehicle I've ever owned was an XJ and I've never worked on a GM 4WD system other than replacing axles and hubs.

From browsing this forum over the years, I know the module (Might be properly known as "encoder" or "encoder motor") is a somewhat common failure point.

Thanks iamdub! Appreciate your thoughts anyway! Cheers, D

 

[George B]

Thanks George, I was trying to deal with some of the more obvious sources of the problem in the simplest ways first, prior to taking the truck into a shop for a scan

If you plan to keep the truck a while invest in a Tech2 and set yourself free from the shop charges for diagnostics.

 

[Joseph Garcia]

If you plan to keep the truck a while invest in a Tech2 and set yourself free from the shop charges for diagnostics.

As @George B stated, the Tech 2 is an invaluable diagnostic and programming tool. I guarantee that you will recover the cost of the Tech 2 (~$350) the first time that you use it to diagnose and resolve an issue. I figure that my Tech 2, which I use sparingly, has saved me well over $1500 so far, in diagnostic work that would have been performed by others.

 

[Rolexus]

As @George B stated, the Tech 2 is an invaluable diagnostic and programming tool. I guarantee that you will recover the cost of the Tech 2 (~$350) the first time that you use it to diagnose and resolve an issue. I figure that my Tech 2, which I use sparingly, has saved me well over $1500 so far, in diagnostic work that would have been performed by others.

Thanks Joseph, I have had the Tahoe for 3+ yrs now and absolutely love it - except when something goes wrong...lol

I will look into a Tech2, but being from Canada, the $350 you paid will be closer to $450 plus tax in our $CDN. But as you say, it’ll pay for itself in short order. Cheers, D

 

[Rolexus]

If you plan to keep the truck a while invest in a Tech2 and set yourself free from the shop charges for diagnostics.

Yes, I relied to Joseph (below), so this is definitely on the radar in the near future. The shop charges I incur up here (Surrey, BC, Canada) are ~150/hr., although this place is GOOD, especially for stuff I can’t do.

Question: Is the Tech2 you mentioned the brand or the generation of scanner? If generation, do you have a mnfr. brand I can get from you to reference? Thanks!

 

[Joseph Garcia]

Thanks Joseph, I have had the Tahoe for 3+ yrs now and absolutely love it - except when something goes wrong...lol

I will look into a Tech2, but being from Canada, the $350 you paid will be closer to $450 plus tax in our $CDN. But as you say, it’ll pay for itself in short order. Cheers, D

Here is where I purchased my Tech 2, and the current price is $275 US. It is a Chinese knockoff, but virtually all of them are today, but they still work as designed. I received my Tech 2 about 3 weeks after I ordered it.

https://www.aliexpress.com/item/1005001627663288.html?spm=a2g0o.productlist.0.0.4c617ff7k5FQYO&algo_pvid=e478db80-28d5-4ee3-b777-034521d96d0c&algo_exp_id=e478db80-28d5-4ee3-b777-034521d96d0c-28&pdp_ext_f={"sku_id":"12000016877986130"}

 

[Rolexus]

Here is where I purchased my Tech 2, and the current price is $275 US. It is a Chinese knockoff, but virtually all of them are today, but they still work as designed. I received my Tech 2 about 3 weeks after I ordered it.

https://www.aliexpress.com/item/1005001627663288.html?spm=a2g0o.productlist.0.0.4c617ff7k5FQYO&algo_pvid=e478db80-28d5-4ee3-b777-034521d96d0c&algo_exp_id=e478db80-28d5-4ee3-b777-034521d96d0c-28&pdp_ext_f={"sku_id":"12000016877986130"}

Thanks Joseph! Cheers, Dwayne