bradland

Replacing ALL the fluid isn't necessarily a bad thing as long as it doesn't involve pressure which forces fluid through the trans.
The preferred way to exchange ALL the fluid is with a series of several drain and fills over a six to nine month period. Proper fluid level is PARAMOUNT !!!

YODAONE

This is vague on SIA's part.

Can SIA elaborate on particulars of rebuild??

Reflash? Capacitors? Resistors? Integrated Circuits? Cold solder joints at connector and P.C. board? Connectors? Flex circuits?

What exactly did they do?

If replacement parts, then demand old components be returned to you.

As a consumer you are entitled to.more particulars.on what exactly was rebuilt.

LEX ES300

I have been considering replacing my whole valve body as well to try to fix my trans issues of no engine braking downhills. To me theres just so many things in the valve body that could fail without throwing a code. Problem is its a gamble throwing money at parts to try to fix trans issues but most dealers just dont seem to want the spend the time trying to pin point an issue. Plus you are always up for new trans fluid each time they try to diagnose issues when they open it up. I can get one for about $1100 in my country and i was going to buy one but I have had other expenses such as I'm due for 2 new struts and new tyres.

LexInFL

When I called SIA to get more details it was like pulling teeth but they were confident that the ECM was fixed!
Anyway I am still in the dog house. The car has gone back to the Lexus dealer and they are going to drain and refill the Transmission and retest the ECM plus a complementary treatment of draining my wallet.
I will update you tomorrow when I get the car back and in the meantime I will just chew on this dog bone my wife has just thrown me.

YODAONE

If SIA is confident it is fixed, then they should be able to articulate on what work they performed.

It is a red flag if not.

Here's how you handle an unresponsive service provider.... Explain that you have to be the customer here...and if they are uncomfortable answering your questions as to what work was performed, inform them then that you must conclude that no work was performed and may find it necessary to inform your Credit Card company accordingly.

Did they repair an ECU that was unrepairable?

Am still on TPS as a possible issue...while yours appears absent, please ask Lexus whether that sensor is integrated into throttle body assembly.

LexInFL

I just got a call from the Lexus dealership and they said the ECU (ECM) has to be replaced so I asked them to give me a print out of the diagnostic tests to show the results. They said there is no such thing, just the fact that it is having this problem means that you have to replace ECU. So all this time I thought they were hooking up some computer and running some software to determine what the problem was. What a joke!!

I spoke to SIA Electronics and they said to send the ECU unit back and they can run through the tests again!
What now?

bradland

Have you verified the fluid level is correct ?

LexInFL

The guy who verified the level is the Certified Master Toyota Technician, he has his own workshop but used to work for local Toyota dealership.
He said the fluid was dirty and recommended flushing the Transmission but I did not do ii because when I asked him if that will fix the problem and he said it might but was not 100% sure.

So today I pulled the ECU out and sent it off to SIA again for them to retest it.

toantran99

Keep us posted.

YODAONE

Repair work done twice??

A bad habit of mine is to keep asking a question until an answer...but promise not to ask again...

I solved the problem you are describing by replacing the TPS...yours does not appear to have a serviceable TPS...so HOW is the position (angle) of the throttle body (blade) communicated to the ECU???

It is hard to believe that this function would be relegated solely by the pedal position sensor...where the 2001-2003 LS430 has both...

Please....ask the Lexus tech to indulge you..he should know.

Meanwhile, since you mentioned SIA in your post, I contacted them to discuss what exactly it is that they do.

The owner finally came on the phone..and he promised to "call tomorrow" and that was from Wednesday. (What is always coming, but never arrives?...Tomorrow)

This is a non-starter for me..

I cannot recommend anyone that does not keep their word..

Since they refused to document their work in the first place, then inform your credit card company ASAP.

rkw77080

For the 2004-2006 LS430, the throttle actuator and the throttle position sensor are all enclosed in a single Throttle Body Assembly (circled in red below).


I'm curious as to how SIA plans to test the ECM... For example, will they simulate a certain speed sensor input signal and observe the corresponding solenoid output signal?

bradland

YODA
The TPS was removed as the throttle cable was removed from throttle plate movement. Instead of sensing where your foot, via the gas pedal - throttle cable - throttle lever, places the throttle plate the throttle motor places the plate where it deems appropriate based on data from the ECU. Since the ECU already knows where the throttle plate is because it put it there it does not need a sensor to communicate it's position relative to the results of the drivers foot on the pedal. The ECU has already decided where the plate should be so reactive data from a TPS would be redundant.

YODAONE

...Lexus advised 2001-2003 LS430 (which I already knew was drive-by-wire) had the "redundant" TPS ,

But this is the first I am hearing that the Pedal Position Sensor had assumed the entire role on 2004-2006 LS430.

In 1998-2000 LS400 Toyota went with a hybrid throttle cable and drive-by-wire setup. There was a pedal position sensor, but it was located on the throttle body and actuated via a traditional.throttle cable. In the event that sensor failed, then further application of throttle would mechanically open the throttle body to provide about 2,000 RPM and a second TPS which I keep referring to would register throttle angle)

It appears Toyota elected to not entirely rely on the pedal position sensor scheme to carry the entire load, but employed redundancy...

So am still advocating that the sensor responsible for determining and, or, measuring throttle position, whether it be pedal or throttle body situated, may be a contributing factor in the harsh downshifting.

Now that everyone understands only one sensor...

Have not heard that anyone has checked the Pedal position sensor.

It would seem that a failed ECU would affect more than a single gear transition, here a downshift...

However, in its operating range the resistance of the Pedal Position Sensor could be notchy in certain areas of the trace sweep.

Replacing TPS in 1999 LS400 solved the notchy downshift and am leaving at that.

Good luck OP.

rkw77080

The difference between 2001-2003 and 2004-2006 TPS design is that the 2001-2003 design, the TPS ( position switch) is a separate part mounted on the opposite side of the throttle actuator on the throttle body, and the 2004-2006 design, the actuator and position switch are integrated into a single part. Functionally, the 2 versions are the same!

See Throttle Body Assembly (circled in Red) which includes the actuator and position switch; and the Acceleration Pedal (circled in Green) which include the actuator and the position switch.

YODAONE

Ok... thanks for your clarification.and presenting a diagram....THERE IS A THROTTLE POSITION SEBSOR contained within the THROTTLE BODY on the 2004-2006 LS430...

So back to my original comment....Have your throttle body TPS checked.

One thing this diagram provides are symbols for the Pedal Position Sensor and Throttle Position Sensor...they are both dual variable resistors...on each sensor one track reads when accelerator pedal is moving in one direction and the other the opposite direction so acceleration and deceleration activity is accurately read by ECU.

If a worn spot in the variable resistor, then ECU's reading of resistance will suffer.

This may be hard to derect without removing the parts and actuallu hooking up to a multimeterto check resistance across the sweep of both tracks of TPS and Pedal Position Sensor

These sensors are electromechanical devices and they do wear out, so worth looking into first.

There is also a motor and (clutch?) in your throttle body to consider.

Sometimes the dealer technician has tthe benefit of having a spare part on hand to assist with trouble-shooting...