find the area of the diagram that shows the pwr sno switch and follow the wire to the number one bcm. than the next diagram shows the white communication wire going from the bcm to the engine computer.

 

This should be interesting. So using the scantool confirmed that there definitely is a problem between the engine ecu and the N.O 1 body ecu (so communications wire / pins or ecu's faulty). Could also be that the body ecu isn't being powered up, so one or more of the grounds and/or 12V supply wires are not connected.

I was just looking at the wiring diagram again to confirm pins:
Are you able to check whether the "MPX" white wire is connected from the body ecu on pin 9 to of the engine ecu on pin 28? On the body ecu its labeled as "MPX2" but on the engine ecu its labeled as "MPX1"

 

ya, ive already checked all communication wires to ecm and from ecm. plus used the scan tool to run a communication test which passed. if there was an issue with comms. than id have other issues like door modules not working, a/c module issue etc... the pass. side bcm i ordered is for an older gs300 from 98-00 instead of my 2002 which is a different part number. im hoping it will have the communication needed to get the pwr mode working and not jack with other things because its a different part number. but like i said its a cheap gamble.

 

also, bear in mind that diagram is for a 2000 gs300 not the aristo ecm. but the aristo ecm still operates the same with one comm wire in and one comm wire out. only those wires are in the aristo plug f59. labeled mpx1 and mpx2.

 

see if you can spot the pwr and sno switch and the comm wire that runs to aristo ecm. this is the actual diagram for the 2jzgte.

 

Yes I to was using the Aristo 2jzgte diagram not the GS300 one. Because you said you did some rewiring so I thought you probably should check whether you have connected the MPX pins to the correct slot.
Didn't you say you did a scan on the system and the body ecu didn't report back? Try going to the live data function and press the power and snow buttons to see if the scantool can see from the body ecu that the signal is being received. This would prove that comms is all good.
Also do an actuation test on the instrument cluster to see if the power and snow lights actually turn on via the module.

 

props for knowing what your talking about. yes all the same train of thought you have is right on with what ive done. I looked at the bcm 1 data stream to verify that when pwr and snow are pressed the bcm sees it. that tells me from switch to bcm is good and bcm is being told to do so. its the comm. signal that's not talking to the ecm properly. I know the comm wire is correct and all because I ohms tested it from bcm to ecm. and the comm wire out of aristo ecm goes to next module in line. its pretty clear that its the code that goes thru the comm wire that's not correct for talking to aristo ecm.
also I did go into the instrument cluster and did a bulb test to get pwr snow bulbs to illuminate. just to verify that they can light up if told to do so. so its all pointing towards bcm being incorrect for aristo swap. plus the bcms from 98-00 have a diff. part number. which just so happens to be inline with the aristo ecm I have which is from 97-00. bc it doesn't have the immobilizer. so my fingers are crossed. after watching youtube videos of aristo swaps, I never saw one that had a 2001 or up with functioning pwr mode.
thanks for getting involved.

 

Great, all your testing is pointing to a differently programmed body ecu like you say.
Comms is working verified by scan tool and wires have continuity
Inputs being received as seen by the live data
Actuators (power / snow lights) are turning on by command from scantool
Cant wait to see the results of changing the ecu!

 

got my pwr mode working. and it makes a big difference in the aristo swap. now when im going 20 and into a turn, the slightest bit of throttle kicks it down to 1st and it takes off like a rocket. before it would just stay in second and be laggy. super excited.

 

Awesome, what was the fix?

 

i swapped my pass. side body control module with an older 98-00 bcm from a gs300.