I need to Find the Gateway module.

I have a 2004 C320. I was having an issue where the engine would not crank. It would crank / fire up and run and shuts off after 2 seconds. It will do that but after the third time, it won’t crank anymore. I would have to disconnect the battery and it will do it over again for three times.

I had a code with the alarm siren, replaced that and the code went away.
Both my key fob would lock and unlock the door with the siren chirping.

When I put the key into the ignition, I can hear the column lock make the sound. I removed the column lock and verify it moving.

Hooked it up to my scan tool and I see immobilizer fault not letting the engine start.

I see the PIDs for terminal 50, and others all working when turning the from off/ on/ crank.

So I bought a complete ECM, Key, ignition switch, ignition lock, and Gateway from a wreck car. Installed the ECM, Ignition Switch, and Ignition lock. Now the engine starts and I can move the car but the Gateway is not connecting the SRS, ESP, and other modules. Where is the Gateway module located on this C320?

Thanks in advance.