kkm871

In the "good old days" a car had zero ECUs. However, then starting in the 70s they found their way into mainstream cars, e.g. for fuel injection and ignition.

More and more were then added: cruise control, AC, transmission, power steering, suspension, instrument cluster etc. However, typically each new ECU was an independent ECU which would not influence the function of other systems when failing.

However, resently the many independetn ECUs have started to be integrated into a smaller number of powerfull central ECUs, this typically reducing wiring complexity but also making things much more complex when different components start to fail, e.g. a failing door sensor may result in the AC or transmission not working properly.

I assume that the first and second gen LS400 are both from the time of independent ECUs.

And now to my question: Has anyone ever listed all the ECUs in the LS400?

Would be interesting to know I think.

LScowboyLS

I compiled a list a while back, seems like the number came to 12

Greg5OH

i can let you knwo when i get home. Factory wriign manual shows the positon of all them.

LScowboyLS

this is correct for a '96

● ECU (ECM)
● Proportional Power Steering ECU
● Cruise Control ECU
● ABS or ABS/TRAC ECU
● Shift Lock ECU
● A/C ECU
● Body ECU
● Tilt/Telescope ECU
● Power Seat ECU
● Driver's Door ECU
● Front Passenger Door ECU
● Wireless Door Lock ECU
● Air Suspension ECU (if equipped)

RA40

iTrader: (6)

The next capacitor project/s to tackle.

Greg5OH

2000 has one per rear door too if im not mistaken

YoshiMan

Imagine if the car was a network of engineers. While some are making complex engine algorithm calculations, and others are monitoring wheel speed variations, one bigshot MIT graduate in the center of it all gets stuck with his first day training manual:

------------------------------------

"Welcome to the exciting career of Shift lock computation! , your job is to make certain that:

If that big pedal on the floor isn't being pushed, don't let the PRNDL thing move.

If the PRNDL thing doesn't say "P" don't let the captain remove the key.

Address any questions to the Field resource guide book located in the storage closet next to the DJ and HVAC stations."

LScowboyLS

engineer humor

reminds me of my days as a NASA engineer in the 1990's

I would play practical jokes on the other engineers, jokes that were so old, they were recycled from my Dad's days working at Budweiser in Florida in the early 60's

Yamae

There are more than 50 micro processors in my 98 Celsior. I added 4 though.

kkm871

I assume those 50+ are then comprised in the different ECU units. Or is the car provided with additional non-ECU micro processors? What are they doing?

Yamae, I recall that you once noted that the '98 facelift LS400/Celsior had completely different electronics being based on a new Toyota CAN bus. Did that influence the numbers of independent ECUs?

Does the CAN bus mean that all ECUs were modified and that no ECU can be swapped between a non-facelift and facelift car?

Also, when the car is provided with a NAV unit, does this mean that control of e.g. AC and audio is incorporated in this unit, or does it mean that the ECU for the AC is the same and just communicates with the driver via a new interface?

Yamae

I have never written that the CAN bus was used for my 98 Celsior but it uses the bus system called BEAN: Body Electronics Area Network. It needed several more years for Toyota to start to use the CAN bus system. I also wrote that JDM UCF20 and 21 aren't compatible with OBD-II.

The EVM displays the map, the AC status, the audio status and others but those have separate each controllers/processors. The bus lines are connected those and the EVM is used as a display unit and a human interface.

The ECU after July 97 is totally different from earlier models although Nichicon PF(M) series capacitors were still used.

kkm871

Sorry for mixing up the CAN bus with the BEAN bus.

Greg5OH

ok, todya I will list all the ECUs i can see int eh wirign diagram.
But im pretty sure Yamae is right in that there are 52 lol.

Greg5OH

1-headlight control RH ecu hi beam
2-headlight control ecu RH (hi and low)
3-headlight control LH hi beam
4-headligth control low and hi LH
5-pps ecu
6-body ecu
7-tilt and telescope ecu
8-shift lock ecu
9-air susp ecu
10-engine control module
11-abs trac ecu
12-wirless door lock ecu
13-headlight beam level control
14-driver door ecu
15-front pass
16-rear door rh
17-nav ecu
18-rear door lh
19=power seat


ok so we got 19. But each of those has multiple inputs (vsc has 3 inputs, 3 individual processors within 1 housing)

rich1995le

Hi, sorry to bother you but it seems if anyone knows the answer, it would be you! My factory alarm goes off from time to time in my driveway without provocation. Do you know how I can permanently disable It?

Would I be able to retain the functionality of the remotes? If I can't, that's OK as the alarm is that annoying to myself & my neighbors. Otherwise it a great car, even @ 25 years old.

Thanks!

rich1995le