Toyota did the drawing, not me

only one box in your entire car has ~100 wires going to it (and 4 separate connectors to hold all of those wires) - that's the ECU
(which also controls the transmission and A/C)

if your ECU is working correctly, any OBD-II compliant scanner will work just fine, including AutoZone's and even this impressive $20 cheapie!

Yes, thanks Yamae.

I removed and disassembled the ecu. along side the ecm. behind the glove box with 4 black multi pin connectors.

it says toyota ABS & TRC & VSC 89541-50110
Denso 079400-7643 12 V
SV 89540 - 50110
100794-7424
and barcode.
I found ZERO evidence of capacitor leakage. Circuit board looks perfect. no smell, connections/wiring/pins perfect.

Could this be a module ecu for something other than the body?
abs- anti lock brake?
trc- traction control ?
vsc- vehicle saftey control?

I do have photographs. Not sure how to post them here..

Mike

99 LS400 wiring issues
 

Here are the 4 photographs of the ecu and capacitors.. all looks great ..

OK, I removed the MPX BODY module left of steering collum.

Removed cover, no signs of leaking capacitors or any melting burnt or abnormal looking spots on circuit board. Connections all good as well.

Also nothing under and around the steering collum looks out of place bad damaged etc.

NOW WHAT????

Guess I will put it in driveable fashion and limp on over for a scan attempt.

The label on this ecu/module is marked
TOYOTA 89221-50090
MPX BODY
123300-4186
DENSO 12 v
e13a-00 0039
e13020187

Wished my camera would take a very clear photograph for ya'll.

Hello ALL,

I removed both ecu's. The abs-tra-vsc ecu disassembled and inspected for capacitor leaks burnt spots, or anything odd in the connections and circuit panel. ALL good.
Also found the Body ecu near steering collum left side firewall behind fuse panel above left foot.
no obvious issues. A possible slight brownish discoloration on the insulator sheet between the circuit board and the body ecu housing (metal).Not burnt or melted. Circuit panel looks great.
Re installed and hooked up scan tool. NO SIGNAL..

A few of the things seem back to normal. The 4 ways /turn work properly now, the horn works normal, the door ajar light works properly for all doors. The seat belt light comes on now but goes off after car starts.Security light is also off now.
NO CODES No Communication.

Still, headlights not working on auto, wipers inop, door locks inop, mirrors inop, power trunk release inop.

Question; How can I get a signal from some computer on this car to give me a code or lead me in the right direction.

I saw a post about body ecu connector G34 pin3. Please help with more info about location this and testing it properly.

Thank you
Michael

I am trying to get scan tool to respond.

I have 4 wires at the OBD II connector
Black w gray 12 v
Yellow grnd
white w tracer grnd
white w tracer grnd

Why would a scanner not receive any signal at this connection?

1. an ECU can have bad capacitors and yet they look fine visually - mine did the first time I took it apart, and out of sheer frustration I pulled it out again 2 or 3 months later, even though everything had looked great, and by this time they were leaking and had almost damaged the main circuit board beyond repair.

2. you need to get the real Toyota factory service manual, for the step by step troubleshooting procedure on these problems that remain, so in other words, you get the door lock working or the wipers working or whatever, and you will likely get everything else working at the same time. you can buy the paper manual set on ebay for ~$200 if you want it right now, or sit back and wait and eventually find one for $75 - In the meantime, you can sign up for Toyota Information System and view or download whatever service manual pages are applicable for a 2-3 day unlimited period for only $15 - this is a service of the factory and required by law in USA.

3. to reiterate and earlier comment I made, I have never seen an ECU fail to communicate the OBD-II codes to a scanner unless the ECU itself had issues or else there was a power or ground problem to the ECU, which is easily checked at the connectors going to it, you will need something slend to measure the voltage and ground while it is connected (i.e. something like sewing needles)


PS - from what I can see in your blurry pics, the caps look OK visually, but this is no guarantee that they are good.

Hi,

I did use a volts ohms tester on the obd II connector.
Black wire 12 v
Yellow wire Grnd
white w tracer grnd
white w tracer grnd

I am well versed with mechanical repairs , however without manuals and scanner it can be difficult.
Dealing with the ECU issue i am uncertain if that OBD II scanner reads the ecm for the engine first? Wouldn't that be where trouble codes are stored?
Does the OBD II scanner read from the Multiplex body control ecu first/second/third?
Does the OBD II scanner read from the ABS, TRC, VSC ecu first, second, third?

Is there a resistance reading on the capacitors, so they can be tested while in the circuit board?

The battery goes dead now. So there is a circuit drawing that was not drawing voltage before.
Quite a complex problem.

If I buy a new mulitplex body control ecu, does it have to be programed at the dealer?

Thank you all for the continued support.

Mike

OK,

I have 12 volts and ground at the OBD II connector.
The Lexus dealer claims if the ECU is NOT responding to the scanner the ECU is defective.

At $2600 bucks I dont like hanging parts on to see if that will work .

Any advice, Please

www.car-part.com and/or ebay.

find a used ecu with a warranty.

1998 ls400 zero OBD II response
 

Thank you for the link to purchase a used ECM w CHIP, (some claim is a must)

There is NO warranty on electrical items, as i suspected. Understand perfectly.

This car is pssessed.

I have nearly the entire dash out now.
Car runs and drives ok.
horns work properly now
headlights work on manual only
door open light and location works good.

wipers work only on high but when first turned on run very slow and then all the sudden really fast. Sometimes gaining speed above the norm. inop on delay and other speeds. washers work good

both fuse panels are functioning properly
No obvious issues inside any of the 3 computers. ( no cap leaks, burnt, hot spots, connection issues)
ALL wiring and connections i have found look great. No mice issues with wires.
Checked several ground connections removed and installed back, all were clean and good.
inside dash and around engine compartment that i could find.

Seat belt lights dont work correctly,
power door locks/mirrors inop
flashers stay on all the time.

Every voltage, ground, ohms test on all i come in contact with has been good.

wth

Mike
mikeee1482us@yahoo.com

ps. I saw somewhere there is possibly an ecm relay...??????????????

:uh:HELP:woot:

just a heads up, you can't just replace a '97 or '98-00 ECU and expect it to work. Those years had immobilzers, and the immobilizer codes are stored in the ECU. So if you swap a new ECU, you would need to have someone with a Lexus/Toyota Scanner (usually a high end snap-on with propriety programming) to reprogram the ECU to your old keys. (Or, have the keys from the car your used ECU came from.)