16196396 ECM swap to 16196395 PCM

I have a 94 GMC k1500 5.7 and Manual transmission.

I took out of a 94 suburban with 5.7 and 4l60E the PCM the engine harness the knock sensor and just about everything else i pulled all the good parts and dumped the empty rusty body at the junk yard.

I completely de-pinned the red and blue connectors off of the suburbans harness and then one at a time pinned in my harness wires into those connectors. I used the guide thats here on this sight for the 7427 upgrade as well as i have my own access to wire diagrams from work as im a service technician.

I also installed the knock sensor out of the suburban in order to match the memcal. Also where my truck had the esc module for the external knock sensing I took the knock signal wire that originally went between the esc and ecm and i soldered it to the knock sensore wire itself so now the knock sensor bypasses the esc abd goes straight to the pcm and the knock sensor is the matching one for that memcal.

Also worth noting the guide on this site says to input a 12v battery wire into brake switch input for tcc to function properly. My trucks harness was short one 12v ignition wire so i instead put that 12v battery wire into the 12v ignition slot F15 on the new PCM. I hope thats okay since i have a stick and no need for tcc?

I now cant get it to start. Its just cranks and it tries to sputter and fire but wont turn over. It back fires out the intake.

With the laptop hooked up to the aldl connector with moates cable 1 setup and tunerpro RT I can connect and communicate with the PCM but the map sensor says 54 kpa. Shouldnt at rest no vacuum atmospheric pressure read like just over 100? Like 103 or something right?

So i thought I missed something with my wire pinouts. I went over my wiring twice with a multimeter set in ohms and I checked everything against the PCM pinouts in the wire diagram that is for the suburban and its corresponding pcm. Pretty much matches the guide on here for the most part too. I also used my trucks wire diagrams to verify the terminal positions at the connectors of each sensor and component on the other end of the harness under the hood and i noted the wire colors but I checked everything based on connector pin outs to avoid confusion caused by mis labeled wire colors etc.

Everything checked out solid except i found that my old ECM fed the MAP sensor and the TPS sensors one shared 5v reference. Meanwhile the new PCM diagrams show that it feeds those sensors the 5v reference independently. Because of my map readings i went ahead and altered my trucks harness. To get through the fire wall to the PCM i re purposed the lo side of the AIR pump solenoid wire and i cut and solder spliced with heat shrink so that now the map sensor and tps sensors both have their own dedicated 5 v reference and id fed from the correct pins on the pcm.

Still wont start and back fires out the intake. I played with the tune a crap ton too. Got a copy of a bin file from InTech on the 7427 PCM swap thread and he said it was from another 350 manual swap and a known good runner. Also the suburban ran fantastically before i pulled it apart. I was originally in $0E but that new bin is $0D so now im running on a $0D bin and definition file etc.

I took the idle VE vs. MAP vs. RPM table and i tried multiplying it by 15 percent at a time and i worked my way up to about twice the stock fuel and nothing changed. I then reduced fuel by 15 percent starting over with the un altered table again and i pulled fuel until it was like nothing left and again no change in it.

If its not the fueling and its not the wiring then what in the hell is wrong with the dam thing please help im tearing my hair out about to pin the old one back in just to get my truck back.

Also the swap guide says that theres a system ground at pin A2 but my diagrams show that as an empty pin? I guess i have an extra system ground that the old computer used cus i have a ground pinned in there but im not missing a ground anywhere else so i went ahead and plugged it into A2.

Also I forgot to mention that my speedo is acting weird as hell. The old computer only had on vss input and the new one has two. When i turn the truck on the speedo hovers around like 30 or 40 mph or so kinda floats around and eventually comes back to zero after cranking or whatever. Also turning the headlights on makes it rise as well. Wtf im baffled. I did check output signal not from drac in the bin but still no change