83 K5 Blazer LS swap issue

So I swapped my 1983 Chevrolet K5 blazer with a 5.3/4L60e, working on it every other weekend it took longer than I wanted but I finally got around to the first start, and it runs poorly. I noticed the intake manifold had a broken nipple for a vacuum port so I swapped it with a spare I had. No change. I did have code po122, ecu was giving no voltage what so ever, no biggy swapped a spare ecu I had, still no better. Only other codes it shows is po200 and po650. I’m at a loss.

I'd check your grounds for the ECM, there's a few of them, and with 3 sorta unrelated codes, that's where I'd start.

Are you running a factory modified harness or aftermarket harness?

Hunter79764 said:

I'd check your grounds for the ECM, there's a few of them, and with 3 sorta unrelated codes, that's where I'd start.

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@iamtherealJayy yup, disconnect the battery, then put your meter on ohms. Then put a lead on the negative battery cable, and test EVERY ground connector on the ECM connector. After that check all your wires to the throttle.

The p0650 is an issue with the bulb/indicator you have wired for the check engine light.....ignore that one....no biggie. Fix that later.

Post results and we'll go from there.

@consti2tion yes factory harness cut down by the same guy I’ve used for a long time for all my harnesses.
@Hunter79764 i checked the ground from head to firewall and it was a little loose so I replaced it with a bolt and nut to the firewall by the hydroboost.
@Camar068 I honestly don’t know where all the grounds are in the harness. My main ground goes to the engine block and there’s a hefty *clump* of harness grounds bolted nearby on the block. The only other ground I know of coming off the engine is the cylinder head? My TPS sensor ground is good.
I’m sorry for the late response, ended up hurting my left ankle and haven’t been able to do a whole lot since I’m in a boot and can’t jump up into the engine bay of the blazer. With the original ECU I get no voltage at the tps, never could figure out why. I had a backup on the shelf I scored on marketplace and it shows voltage but still stumbles off idle, or I suppose with any sudden throttle input change? I also remembered that when I put the engine in I had broken the range selector and replaced it but never got it plugged in, I connected it and still no change. Once I get it up in rpms it will hold it but any sudden increase in throttle will make it bog out. Tried unplugging mass air flow and still no change. My best comparison to how it’s acting is when my air filter fell off my k10 and the maf wasn’t reading.

if you have the range selector unplugged on the trans, there's 2 wires I believe that need to be connected together on the ECM. Check the LT1swap chart and it should say it. Something in the nature if "if no range sensor" do this.