Jack Hall

I recently had my ‘99 Suburban k2500 totaled out after an accident, and I picked up an ‘89 K3500 to replace it. Now my 3500 is acting up, what I’d like to do is swap my trusty ‘99 OBD2 Vortec 7.4 into my ‘89 OBD1 with TBI 7.4.

would the harness/ecu/plug-in from my ‘99 swap directly in? Any splicing? Do I need to buy an adapter to do this? Just looking to do the swap fast and don’t want any hang-ups with the electrical. Also, O2 sensor? The 3500 has a manual already and the odometer/trip already doesn’t work so no issues there

Irish_alley

not sure about the 99 but on the 89 all ecm crap is through a wire harness on the passengers side. the bulk head connection has some wires to sensors and the key wire for the starter but for the most part the ecm crap is on the passengers side. when you swap the 99 over youll have to figure out the sensors and ecm crap. if your 99 has Ox sensor then youll need to incorporate that also. not sure year gm started it but you also have a rev limiter to deal with and that usually is fixed with making the ecm think the trans is in "N". this shoudnt be too complicated but its not weekend project.

Jack Hall

I believe I can tap an 02 sensor in if I have to, other than that is there any sensor I’d have to splice into or update that isn’t located on the motor itself? Personally as long as I got the motor running right/turning with the key, and maintained working lights and wipers, I would be fine taking the time to rewire anything else as needed. I just need the essentials working. Would doing a Megasquirt ECU be easier?