PCM Ground locations? 5.7L 2000 Chevy

[eXo0us]

2000 Chevy Express 3500 5.7L

I'm chasing a single cylinder misfire code and recently I got knock sensor code. And sometimes just other random errors - which then turn out to be nothing.
Going back to my electrical engineering days first step of troubleshooting: Check Power and Grounds. Power is good - when running

With everything checking out I found in the workshop manual the step "Check PCM grounds"

After looking through the wiring diagrams I'm at a loss - where does the PCM grounds to? The engine block itself? The heads? The only ground from the PCM harness. I found connects to the A/C-compressor bracket - which in turn connects to the Block.

 

[Caman96]

2000 Chevy Express 3500 5.7L

I'm chasing a single cylinder misfire code and recently I got knock sensor code. And sometimes just other random errors - which then turn out to be nothing.
Going back to my electrical engineering days first step of troubleshooting: Check Power and Grounds. Power is good - when running

With everything checking out I found in the workshop manual the step "Check PCM grounds"

After looking through the wiring diagrams I'm at a loss - where does the PCM grounds to? The engine block itself? The heads? The only ground from the PCM harness. I found connects to the A/C-compressor bracket - which in turn connects to the Block.

Might be a good time to inspect/replace all your grounds. At least you can check that off and like you pointed out, vital for function.

 

[eXo0us]

Might be a good time to inspect/replace all your grounds. At least you can check that off and like you pointed out, vital for function.

I'm in the process of doing that. Just cleaned a bunch of ground points and ordered a new engine ground strap.

Just wanna crowdsource knowledge here to where those PCM ground points are - so that I don't miss one.

 

[Caman96]

I’m probably wrong, but I don’t know of any specific pcm ground other than somewhere in its harness grounding to the frame or body. Maybe I’ll learn something here.

 

[eXo0us]

I’m probably wrong, but I don’t know of any specific pcm ground other than somewhere in its harness grounding to the frame or body. Maybe I’ll learn something here.

Pretty sure you are right - it's likely grounded through the wiring.
According to the 0411 Pinout it has half a dozen grounds listed - wiring color BLK/WHT for almost all of them. But I don't find a document which tells me where they are going.

 

[xXxPARAGONxXx]

2000 Chevy Express 3500 5.7L

I'm chasing a single cylinder misfire code and recently I got knock sensor code. And sometimes just other random errors - which then turn out to be nothing.
Going back to my electrical engineering days first step of troubleshooting: Check Power and Grounds. Power is good - when running

With everything checking out I found in the workshop manual the step "Check PCM grounds"

After looking through the wiring diagrams I'm at a loss - where does the PCM grounds to? The engine block itself? The heads? The only ground from the PCM harness. I found connects to the A/C-compressor bracket - which in turn connects to the Block.

So, do you have volume four of the 2000 service manual? If so, that has the electrical schematics for the ground distribution.

> Volume 4
>>Body and Accessories section
>>>Wiring Systems sub-section

I believe the first schematics will be of the Power Distribution. After that you should find the Ground Distribution.

Based on the 1999 manual I have, which should not be much different (although there are some electrical differences), "Cell 14: G103 and G104" shows that VCM connector C3, pins 17 and 18 (both described as "VCM Ground") ultimately ground to grounds G103 and G104.

Per service manual G103 is located "On the right front side of the engine, near the thermostat housing". G104 is located on the "Backside of the right cylinder head".

 

[Caman96]

You must be registered for see images attach

This is a 96 5.7, just as an example.

 

[eXo0us]

> Volume 4
>>Body and Accessories section
>>>Wiring Systems sub-section

Thanks, I guess I got a different documentation set then you have. Mine is an a 1994 - 2006 Express Van / Workhorse RV compilation.

But you still gave me a good hint: I'm searching at the wrong spot in the manuals. I was digging through the Engine sections (only 5000 pages), while the grounds are in the Body wiring (1400 Pages) ... lol OK.

 

[eXo0us]

You must be registered for see images attach

This is a 96 5.7, just as an example.

Thanks for that picture. That ground wire is attached to my A/C bracket and the thermostat stud is barren.

One of my previous owners swapped the engine and apparently forgot where the grounds should have gone...

The rear grounds are attached to the bellhousing of the transmission instead of the driver side cylinder head. No wonder that I electrical gremlins.

 

[Caman96]

So correcting them solved your issues?