Hello,
Initially I asked for help on 2carpros, but for some reason eventually not get response.
I also look everywhere for information and get through wiring diagrams many times.

It is my dad's vehicle, so I able to work on it on weekends.

Vehicle suddenly show VSC on panel, and cut power. Transmission begin changing gears not smooth. Error code show c1203 or stomp code 53. No check engine.
Check wires between ECU and SKID - all OK, communication OK (with voltmeter and cheap oscilloscope) until throw VSC on dash, then freezes and stay on same voltage.
Error throwing when vehicle not moving, and nothing touched- only start engine.
Replaced ECU, SKID, yaw, acceleration, VSS on transmission, TPS (found flat spot when test), check ABS pump and ABS sensors, check grounds, power to ECU and SKID. After each replacement proceed with zero ground reset. Difference is only time of throwing VSC. At the beginning it was almost immediately, after all changes - about 3-5 minutes after starting vehicle. Now it get back, after battery unplug about 1.5minutes, w/o unplugging about 15-30 seconds.
Freeze data show: vehicle moving 0.62mph, breaks pressed all the way, stop light on, vehicle spinning, steering wheel turned all the way (show correctly only after 24mph per specs).
When I check all readings via Techstream on ECT ECU and then on SKID, I found that RPM’s on ECT ECU is stable and equal to tachometer readings (about 700 RPM's), but readings of RPM’s on SKID is all the time jumping from 0 to 1400 on idle. Seems that might be root of the issue.
However, I can't find any information how RPM readings get to SKID ECU - guess through TRC+/TRC-/NEO.
After many researches, I suspect that it might be something with crankshaft sensor/wiring, however not sure why on ECT ECU and tachometer all looks OK, is it flattened and show average and SKID get coded "straight" readings?

Please advise where to look, currently I'm completely lost.

Thank you

 

Thank you for posting but to set the expectations right .. your issue as well as your personal insight is way beyond the average CL member's. Even then I hope some expert here would reply.

I might suggest trying the Toyota forum [highlander is the twin sister].

Salim

 

Thank you, Salim,
I understand that there is not many experts on forums, but who knows, there are many unrecognized gems in our world. Sometimes not expert might guess perfect idea.
Thank you!

 

Wondering, if someone able to check RPM reading on ECU and SKID, is it same? How RPM changing on SKID side?
Thank you.

 

Have you try to check the RPM reading on the ECU and SKID with a DVOM that can read RPM and/or Hz, check the signal at pins NEO, ENG+ and ENG- of the connector A39.

Also check the parking brake switch.

 

Thank you for checking.
If I will have a time on weekend, planning to measure signal from crankshaft, then to tachometer from ECU, and again NEO from ECU.
If crankshaft sensor would look OK, then if Tachometer and NEO signals would look same, will split Tachometer signal and send instead of NEO and see what happening.

Parking break switch is tested and working as expected, also recognized correctly via Techstream.

Here is readings, I believe in this order: TRC+, TRC-, ENG+, ENG-, NEO and NEO.
Also Techstream readings:

SKID after start, ECT ECU show around 760 RPM, on SKID 319 RPM

SKID after start, ECT ECU show around 760 RPM, on SKID 0 RPM


ECU before start

ECU after start

SKID before start, error already registered but not throw VSC on dash


TRC+

TRC-

ENG+

ENG-

NEO

NEO

Thank you!

 

Your SKID ECU might have received malfunction signals from the ECM that it can't understand, or the issues are in the SKID itself. I don't know if the issues are still in the ECM, SKID or the wiring of the pins NEO to NEO, TRC+ to TRC+, TRC- to TRC-, ENG+ to ENG+ and ENG- to ENG-.

I know you have mentioned that ECM and SKID have been replaced and the wiring has been checked, but I would like you to revisit all the above once you have tested the crank sensor signal.

Also check the TC terminal of the DLC to the TC terminal of the SKID and TS terminal of the DLC to the TS terminal of the SKID. TS terminal is next to TC terminal to the left.

I have attached my SKID ECU's and ECM's rpm readings and Deceleration sensor G conversion values.

Your Techstream shows there're 3 fault codes? What are they?

Hope this helps and best of luck for this weekend's projects!

 

 

 

Great! Thank you for information and DLC advice!

Weird, it is looks like "3" in errors on the picture, but it never show 3, always been only 1. I just double check on original one, and it is "1". Anyway I will try to re-run/test everything and report back.

Thank you very much!

 

I'm sure you have the repair/service information for your vehicle. I just want to compare notes make sure we are both on the same page.

I have attached the Engine and ECT ECU and SKID ECU connectors, terminals for each connector, pinout values and diagnostic parameters. Pay attention to terminals 6 (IG1) and 7 (NEO) of the connector 39; each terminal should be measured at 4 different ground terminals.

Check the 15A ECU-IG fuse. Do you recall if the VSC buzzer making sound? Also check the steering angle sensor. The NEO and TRC waveforms don't look normal!

 

 

All make sense, and more information - more details.
Hopefully it would be enough time for everything, I'm planning to get there on Sunday.
Unfortunately, testing by "pulse generation" will not work in this case, that is why we got oscilloscope - it has pulse generation.
Buzzer worked when I run test on Techstream.
Steering wheel angle sensor also use to work (once reach 24mph) on Techstream. I also removed steering wheel and test it straight.

For last 1/2 year I just test everything related one by one.
I recently found full manual and already twice get through it - https://sinref.ru/avtomobili/Lexus/0..._kopia/000.htm

And thank you for your help!

 

Got sick today, will try to update tomorrow some info.

 

Sorry, was not in best condition when measure. Here is what I was able to collect.

ICU-IG - ok, same readings as on fuse, about 12v.
crankshaft minus show to ground 0 MOhm, with dropping time to time, not sure if it should show something to ground, since it is going to ECU.
And I don't like readings from + , should be different waveform.


From crankshaft +

From crankshaft +

From NEO

From NEO

From NEO

Not sure - crancshaft - ?