M122 blown 5.3 in my 99 silveraydo

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Finally had a breakthrough, and its what I said. Oversight on my part, because I assumed "pcm ground" and "ground" were one in the same on the pins

Which they are, becsuse they bus together and bond in the harness, but the instrument cluster, BCM, and a bunch of other stuff behind the dash needed "PCM ground".

I traced it back to the C2 UHEC bulkhead and I was just simply missing a ground pin...

I added one one, terminated it at the fender where I have other grounds terminated, then checked for battery (-) at the cluster and DLC and now we are solid

So i connected the battery and now my instrument cluster works with key on!!!!!!!!!!!

I connected my laptop to the pcm for the trans and instrumentation and pulled the file off

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04 express van.... that was the pcm i bought off the internet


TPS showed throttle activity, CTS showed half of the actual ambient temp, so i must have a holley coolant temp sensor in there and not a LSx cts. No biggie.



So i then hooked up the holley. It switches on and off with a key cycle!!

I went to pull up the holley data logger but it said I needed to update the holley. No big deal.

So at least im making progress forward and not backwards now!

 

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Made some excellent progress today.

Made a first attempt to update the holley. Bricked it thanks to my computer going to sleep mid update.

Recovered it, updated it.
Got the i/c pumps working, after switching their polarity and damn do they move water like a MF.

Got the e fans working but only 1 turns on hi/lo

I think i just need to switch the 2 input pins at the plug. That harness worked as intended on the 79.


Got the BBV solenoid powered. Duty cycle moves with throttle movement.

If I ground out the " tow haul" input it deactivates the bbv as intended.

Flex fuel sensor registers 0% but I confirmed it does sweep thru the voltage.


Waiting on that new relay to finish and confirm tow haul works,

And lastly I will need to revist the 2 step and I think actually use a relay to trigger an output for the holley to see. But ill dig in tomorrow.

 

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Waiting on that new relay to finish and confirm tow haul works,

What i meant by this was, the relay i bought apparently was intended to be triggered thru an inactive, dead, unpowered (idk how many more adjectives I need to get the point across) switch.


My dumb arse put (-) to the trigger which instantly blew the microchip up in my face, LOL

So i dug more. And found this.

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This is what i shouldve gotten the first time.

It latches / unlatches ground or positive with a momentary input, and when the 12v supply is killed (ign switch) the relay defaults back to "open"


I ordered that and a 1/4 watt resistor and some .1uF capacitors to filter out electrical noise on the IGN circuit so it dont blow up again.

 

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AT LAST

SUCCESS


I was half tempted to upload a youtube video but I figured explanations are enough.

My new bistable latching relay was a success. I soldered a .1uF capacitor between the ground and ground trigger (tow haul) and a small 1/4 watt resistor inline with the tow haul trigger button....

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Added some bracing for the fragile circuit, and glued this relay behind the dash.


AND IT WORKS AS INTENDED

Key on, relay is open. Holley sees no signal. Tow haul is OFF.

I press my tow haul on my shifter stalk, the relay clicks on, latches ground to the holley, and the little red LED lights up. (The instrument cluster also shows "tow/haul" )

Press tow haul again, and the relay turns off.

I also made sure it resets with key off, and it does. Just like the factory tow haul.

I confirmed the boost bypass valve MAC valve moves with throttle, and as soon as i press tow haul, it kills the MAC valve which should result in full boost instantly.


It might seem like a small deal, but its been a little journey, lol.
Its finally done !