Hello to all. As I go through my stock 5.3 wire harness, I noticed that on the c2 under hood connector that F6-PCM ground and F7-ground. If I connect F7 & F6 together, will this provide my harness with the proper ground? (Note-The grounds will be connected to the cylinder heads and the engine block. The vehicle will be properly grounded the engine block and battery). If not, where does the PCM get it's grounds from?

 

(I've been trying to think of a better way to phrase this, but...)

Electrically-speaking, a ground is a ground is a ground, any specific point in a ground is the same as any other point, so in that sense it really doesn't matter - BUT, from all of the reading I've done on here, the ECM requires a good, clean ground, otherwise you're liable to run into some potentially-odd, difficult-to-troubleshoot problems.

So, to rephrase that, I'd say that tying the grounds together as you describe shouldn't matter at all - just try to be very sure that you have clean, low-resistance connections between the battery's negative terminal, the engine, the body/chassis, & whatever else needs to be grounded. Clear as mud??

(I'm sure that someone will hop on here to "correct" me, but be nice - I got my electronics degree YEARS ago!)

 

I would agree with V8Rumble. I would add that any ground that is related to the engine harness and ECM should be grounded to the back of the head.

You don't want to have the grounding circuit taking some high resistant path throught the body or chassic then throught the battery before it complete the circuit, when the short path to complete the circuit is directly to the engine in the first place.

 

Thanks for all the replies. I'm gonna rephrase this question. I know a ground is ground is ground. I got that part. what I want to know is, in a factory wire harness, on pins 1 & 40, on the blue PCM connector and pins 1 & 40, on the red PCM connector, per lt1swap wiring schematics, it states that these pins are PCM grounds. What are pins 1 & 40, blue/red fastened to for the PCM grounds? Does the F2 under hood connector combine F6 and F7 to make this possible? The reason I ask this is I'm not going to remove all the wires in the harness. I'm looking for a fast way to run this harness in a stand alone fashion. Thanks in advance. Clark.

 

this is an example of what Im referring to. I just may connect F6 & F7, use the (3) ground points that I found in the factory wire harness, and see if this works.

 

V8Rumble, bczee, I don't y I doubted you. Between u both, there is a wealthy library of information. A ground is a ground is a ground. I tested the wires again with my multi-tester and your rite. All the grounds are connected through the split pack some how. Sorry for wasting a thread. I guess the first time I tested the circuits the multi tester wasn't working properly. Thanks again my friends.

 

The ground splice pack is about 4 inches from the MAP sensor on the branch that runs on top of the intake(RH).

 

Thanks for the info lsxranger94. I'm not gonna look for that splice pack either. I'll take your word that it's there. I'm trying to make this harness stand alone as easy as pie.

 

Heck, it's not "wasting a thread" as far as I'm concerned, it's confirming that your understanding is correct and/or perhaps finding a new/easier way to do something! As far as I'm concerned, it's better to ask a "dumb" question (and feel like a dummy) than it is to make a mistake that could put a dent in your wallet - and BELIEVE ME, I've looked like a dummy on here more than a couple of times!!

Glad to see that it's working for ya, good electrical grounds seem to be one of the more-common missteps that people take. Good luck with the rest of the swap!!

 

As all have stated, grounds are your best friend. A good case in point are any older Corvettes. Grounds that ground grounds is probably the best way to describe this. I have learned that you can't really have too many.

 

I think the "ground is a ground is a ground" logic goes out the window when dealing with modern electronics. There is such a thing as a ground loop which can cause all kinds of gremlins in electronics. Grounds conduct current and any path the current takes to get back to the battery will have some resistance. Any time there is resistance, there is also a voltage which is needed to overcome that resistance. That voltage represents something greater than ground and if it's high enough it can cause electronics to misbehave. Whenever you join multiple ground to one point and then take a combined path to the true 0volt of the battery, you are combining the currents for each of those grounds which can raise the voltage at their juncture. For normal loads, that small amount of voltage usually is no big deal, but for a signal it can be problematic. In the electronics of the ECM there are transistors and conditioning can depend on very particular signal levels. Sometimes a momentary spike (like what you might get from an injector or ignition coil) can cause a transistor to change state which can make the ECM react to an erroneous signal. Or when dealing with analogue signals like the coolant temperature or MAF, a small increase in voltage may represent a big change in the measurement. That is why many of these sensors have dedicated ground or even dedicate signal and ground coming from the ECM instead of from a common point elsewhere on the chassis or harness.

Personally I think your best bet is to replicate the junction points and wire sizes that were originally used on the OEM application. The OEM system was validated in performance testing and you will have a high degree of confidence everything will play nice.