1971 GMCe Lexus GS450H BMW 530e Tesla Model S Electruck [Upgrade]

[Gregski]

so one of the first mysteries that I solved was: How does the transmission harness connect to the Inverter harness? What magical and mysterious black box sits between the two, if any?

and once again the Lexus "components" schematic provided minimal help, as they completely neglected to even label this Holy Matrimony as shown in the screen shot below (just a kind reminder the blue harness is the Inverter harness the green (olive) harness is the transmission harness)

[and I don't apologize for the mundane and repetitive and excruciating detail as there are folks viewing this of varying levels of experience and familiarity with our beloved GS450 "haych" Unicorn transmission]

[Gregski]

worth noting is the difference in the two transmission resolver plugs (gray is 8 pins, black on has 10 pins) which mate with the matching set coming from the Inverter, the black one runs to Motor Generator 2 aka MG2 it has two extra pins, those blue/red wires they are for positive power going to the Inverter

they connect to these two blue wires on the Inverter plug

[Gregski]

For Reference Only:

In addition to mating with the Inverter harness on the passenger side via the two Resolver Plugs, the transmission harness mates with it in a second spot on the driver side via a long and narrow fuse block adapter thingie

this is just for demonstration purposes, we end up not using all of this transmission wire harness (in the lower right corner of the photograph)

[Gregski]

ok I know we are pounding a deceased stallion into the after life, but let's just get through it

I want to give you a birds eye view of the entire Inverter wiring harness so that once we start unwrapping it you will know which branches we are going down or up

[Gregski]

PLEASE DO NOT BUY JUST A SHORT INVERTER PIG TAIL

... and here's why

do you see how if we unravel just 8 or so inches past the Inverter branch and into the main branch we get the Resolver connectors with it, this is so HUGE you have no idea, or maybe you do, ha ha

[Gregski]

and if we follow the main branch North for about a foot to where it just comes to another main junction we can save ourselves a ton of even more headaches

See how those brown (shielded conduit grounding wires) loop back on themselves, well if you get a pig tail those get cut in half. Also see how after that there really are not that many wires that continue on from the Inverter plug!

[Gregski]

alright let's complete unwrapping this Inverter plug harness and see where it ends up, after cutting across from the passenger side to the driver side along what I can only imagine was the firewall, it heads South to the Electronic Control Unit ECU (not to be mistaken for the Engine Control Unit or the ECM Engine Control Module) there is no Engine Control Unit (I made that up) and it's the "transmission harness" aka Engine Wire that plugs in to the ECM Engine Control Module

Confused? great, hang in there, the above is not important as we lop all that off anyway

below you can see the two ECU plugs, all but two wires from the Inverter plug run to the larger plug, and only two go to the smaller one (and I am pretty sure we don't end up using those two)

the four Synchronous Serial Communication shielded pair cables [pronounced: super important] run from the Inverter plug to the larger ECU plug, on the left below, we cut those at that plug, keep those exposed wire ends as long as you can, you'll thank me later when you're crimping and building your VCU connector]

[Gregski]

alright with the Inverter Plug / ECU Connectors divorce being final, we are only left with three final wires (two white/black stripe negative ground wires) and a single black wire that we will not end up using

and this is what our extracted harness looks like up to this point, after we tidy up a little bit

[Gregski]

the two white/black stripe ground wires run to this thing

the mother of all splices

this is somewhere near the fuse block on the driver's side

I swear there's an MIT grad in the basement of the Lexus headquarters building in a room with no windows, tasked with designing unique connectors, her only technical requirement: make the next one completely different than the last! [her older sister a Cal Poly Magna cum laude works for GM]

[Gregski]

I chased the remaining black wire till the bitter end, and if you choose to do the same you're in for an unpleasant surprise (thank you Mr. Lexus)

you could just cut those three remaining wires before this mess, but I decided to take one for the team

[Gregski]

this is absolutely fascinating, the only thing better would be if there was a video...

oh God Noooo, seriously?!?!?!

[Gregski]

so just when I thought I was done with the Inverter harness, I went and tried to wire up the oil pump controller to the VCU and thought, hmm the oil pump came with a short black low voltage harness that connects it via two small plugs to the oil pump controller, but what plugs in to the controller to control it?

[Gregski]

ah yup, it's that dreaded Inverter harness aka Engine Room Main Wire

so here we go again

[Gregski]

#55 - Oil Pump Motor Controller

[Gregski]

first we remove yet another plastic housing

[Gregski]

a little peak at a wiring diagram never hurt nobody

[Gregski]

and we chase down the first wire, brown going to the ECU larger of the two plugs

[Gregski]

second verse same as the first (black wire this time)

[Gregski]

that brings us to the fuse box

I gently tore the lid off this stupid impossible to open plastic clip housing, I have zero patience for old crusty plastic clips, they never act like they were supposed to and I always break at least ... ... ... All of Them!

[Gregski]

I used great care and extreme caution to gently persuade the complete relay modules out of that forsaken fuse box contraption

[Gregski]

so then that led me to the relay that the oil pump controller uses, super cool

[Gregski]

I hope to repurpose this relay block for the oil pump and some other stuffs

[Gregski]

and here is the entire transmission oil pump controller wire harness

[celeron55]

This *is* absolutely fascinating. And thanks for the laughs. Having partially dipped into this myself before this is very relatable and useful.

[Uppertown]

Keep up the good work! I wish people covered other topics as thoroughly.