98 k3500 driving me insane. Wiring harness issues

[Dually From Hell]

UPDATE : I Finally got it running.. the issue was it was mssing the ignition control module.. I knew I had a mystery plug I couldn't identify but I was guessing it was for the map sensor as I thought the map sensor was towards the back of the intake. it's really kinda stupid but then again if u never seen 1 of these 454 engines b4 like I hadn't how was I supposed to know it was missing?

 

[Dually From Hell]

Ok so more electrical issues. I'm using the original ecu it has 4 plugs. The harnes I got from the 2500 ext cab has 5 ecu plug it has a 2 wire plug in middle top of ecu. What are they for? Next issue no brake light I step on the brakes the horn blows. Oil pressure gage is pegged. New sensor installed same issue. Fuel gauge reads empty in park full in reverse empty in neutral ect. Temp gauge does nothing at all. I think it's a pinout issue between that 2500 harness and my dash harness

 

[smokymtn65]

you may need to get an alldata subscription
or buy a pin out spread sheet from @Lextech

 

[df2x4]

you may need to get an alldata subscription
or buy a pin out spread sheet from @Lextech

The PCM pinouts for '98 can be found in the factory service manuals here for free.

https://www.gmt400.com/threads/88-95-service-manuals.43575/

 

[Dually From Hell]

Ok I will try that

OK so I wanted to update this thread I hate when people leave threads on answer so the issue with the truck not starting was yeah starting was I kept finding this one plug that was not connected to nothing and started looking on the Web at pictures of 7.4 since I've never had 1 before and found out that the Ignition control module was missing off the engine so I went to the local junkyard junkyard got 1 off at 3:50 Plugged it up and the truck fired right up