Fix for ABS, VSC TRAC, VSC OFF, & Brake lights remain on no CEL, or how to repair an ECU (1 Viewer)

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Hopefully this post saves you some money by showing you how to potentially repair your skid control ECU rather than replacing/buying a new/used one (skid control ECU part #
89540-60160). These instructions do require the ability to solder surface mount components and use either an oscilloscope and/or ohm meter. It can also be useful to have the Techstream cable and software as this is the quickest way to check that you can communicate with the skid control ECU. This diagnostic approach could potentially be used to repair other ECUs with a similar failure mode (no communication).

TL;DR if you diagnosed a bad ECU, and if you have some technical skills, you can figure out what component has failed. In this case a ceramic resonator failed which provides a clock to the micro-p. $0.50 later the ECU is working again.


The symptoms:
Recently, I had my 2002 LX470 experience the following condition; ABS, TRAC, VSC TRAC, VSC OFF, and break lights all came on.



No CEL and no skid control buzzer.
I never experienced any kind of sudden breaking or stability issues that others have reported.
I was able to pull codes using the on board diagnostic system shorting Tc and E1 on the DLC1 port. I don't remember the codes it gave but it was something like front wheel sensor. So I checked all four wheel position sensors and no trouble found.

So I reset the code and performed a zero point calibration. I've heard that the ZPC can often times fix these issues. The lights were all still on. Another strange thing was that the ACH or vehical height lights were sending the codes out instead of the VSC lights. This must be a logic and/or for when the skid control ECU goes out? Who knows.

The diagnostic troubleshooting process can be found here: http://dustbird.com/ih8mud/FSM/Diagnostics.pdf

However, in my case, there was no communication with the ABS ECU on Techstream which indicated that the ECU really was bad.



Notice in the image above there is an asterix in front of the ABS skid control ECU. *ABS/VSC/TRAC. This is an indication that there is no communication with the ECU.

So I contemplated with buying a used ECU for $750 on Ebay but I found a few companies that would repair the ECU for ~$250. g7computers.com is one and the other I found is moduleexperts.com. But this got me to thinking that if they can fix it then I should be able to.

Edit: This is where to find the ECU:
It's under the dash on the driver's side right next to the brake pedal. You have to get on your back to see it.
There are 2x 10mm bolts and 4 wire harnesses. The 4 connectors have a clip in the center that need to be pushed in to release.

1600971746553.png



From ICCE:

1600971920286.png



I opened the ECU box to take a look. First I did a visual inspection looking for anything burnt or obviously bulging/exploding caps. All good.

Then I grabbed an oscilloscope from work and looked at the oscillator/clock signals.

Imgur


Notice the three large chips. These are three separate micro-controllers that independently handle ABS, VSC and TRAC. Each of these need a proper clock signal to function properly. Using an oscilloscope, I probed X1, X2 and X3 for a clock/sine wave. X1 and X2 are crystal oscillators and both had a strong clock signal that matched the frequency marked on them, 20MHz and 16MHz. X3 is a ceramic resonator and had only a 0.9V DC, no clock. So I ordered a new one on Digikey and replaced it.

Imgur


In the center of the image is the replaced 4MHz murata ceramic resonator from Digikey (part# CSTCR4M00G55B-R0). Unfortunately, the physical size is smaller that the original but I was able to make the solder connections without shorting to ground. The bad resonator had ~780 ohms between the two outer terminals. These should be open, infinite resistance. With an oscilloscope, there should be a strong sine wave/clock signal present. On the bad resonator, there was only ~0.9V DC.


Here is a schematic of the circuit. The resonator component include the CL1, CL2 and X. Rd is external and can be seen on the PCB. All other components are inside the micro-p chip.
upload_2019-2-2_13-10-13.png


If you don't have a oscilloscope to verify the clock, you can simply ohm out the resistance with a DMM to check if the ceramic resonator is bad.

Edit: Found a properly sized ceramic resonator. I have installed and validated that this is a valid replacement. Ordered from Newark.

Newark Part No.Qty OrderedMftr. Part NoYour Part NoManufacturer / Description
16AH094125AWSCR-4.00CPLA-C33-T4ABRACON AWSCR-4.00CPLA-C33-T4 Resonator, 4 MHz, SMD, 3 Pin, 30 ohm, ± 0.5%, AWSCR Series


1602612283675.png



Bad part measurements in circuit (center pin = ground):
Left pin to center pin (gnd) = 8.73k ohms
Right pin to center pin (gnd) = 7.96 ohms
left pin to right pin = 777 ohm (this should be open or infinite)

Bad part measurements out of circuit:
left pin to center = open
right pin to center = open
left pin to right pin = 768 ohm (this should be open)

Good part measurements in circuit:
left pin (1) to center(2) = open/high impedance (Mohms)
right pin(3) to center(2) = open/high impedance (Mohms)
left pin(1) to right pin(3) = ~8.7k ohm (not sure on the range but +/- 10% should be fine.

As I mentioned the new part I ordered from Digikey (CSTCR4M00G55B-R0) was physically too small. The important parts are 4MHz and 39pF capacitance.
When soldering, the new smaller part needs to be on an angle as to not sort out between pins. There may be a larger part that is the same as the original but I haven not been able to find any direct replacement parts.AWSCR-4.00CPLA-C33-T4

Edit: I have ordered several of these parts and can help anyone that needs it. Just PM me.


I hope this helps someone and let me know if you need more help or have questions.
If you want to get Techstream and the cable on the cheap, see this thread.

Repair 2002 Land Cruiser/LX470 Toyota Skid Control ECU, replace ceramic resonator
https://www.westfloridacomponents.com/mm5/graphics/F10/CSA358MG300DETF.pdf
New ECU: 89540-60160 - Genuine Lexus COMPUTER ASSY, SKID CONTROL

Edit: The physical size of this resonator is 7.2mm x 3mm. Height is 1.5mm.
Murata does not appear to make a resonator in this size (or even close to it)
AWSCR-4.00CPLA-C33-T4
 
Last edited:

Ayune

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I live for this stuff!

Really, I actually do it for a living and it’s fun to see other like-minded folk debugging and demystifying it for everyone. Thanks!
 
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Yeah, circuit design is my source of income and I love debugging and fixing things. It always amazes my wife when I dig in and get to the root of the problem and fix random household electronics. I have literally saved many thousands of dollars over the years by just going through a debug process rather than throwing the thing out or getting it fixed elsewhere.

I was actually really skeptical that a passive device like this ceramic resonator could go bad. I really thought the micro-p was bad.
But for $0.50 (plus $5 shipping) it was worth taking a chance.

Once I removed the old component and measured the low resistance across the terminals, I knew it was the culprit.
 

Ayune

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Yea, they are ceramic after all and can crack from an innate flaw or shock. Trimming the leads of a through-hole crystal after soldering is a great way to crack it. We learned to use dull cutters to ‘score’ the leads, then bend them until they break off. Assembly yield skyrocketed after that.

Ceramic caps can also crack if subject to thermal loads like on LED MCPCBs. Can’t see it visually but when you reflow one end of the cap it splits in two.
 
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Thank you @FJRyder !!! I had the same symptoms, pulled out the o-scope and also saw no clock signal on the 4 MHz ceramic resonator. Ordered a suitable replacement part and replaced it. All good! Wish we could find an equivalent part in the same form factor. I would have made up an interface board, but didn't want to spend the time. The $0.50 part repaired my $1700 part! I have ABS, A-TRAC and VSC again!
 
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Hello All,
If possible, I would like to ask for your help please:

1. My lights are up since last week...and I hope to follow your method. I realized all the doc/manuals here are for USA version; i didn't see this ABS/VSC ECU under the steering area (the main Engine ECU lives behind the glovebox)... Where exactly is this ABS/VSC ECU in the 2000 Lexus LX470 for AUSTRALIAN version?

2. Do you have any manual on this ECU? Where can I get one please?

I see many people having this exact problem, yet not many have solved it with your method... it would be great if we can all spread the good work here.

Thank you in advance.

Quan
 
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Many many thanks FJRyder for this information. Just completed repairing my ABS ECU that was not communicating with techstream exactly as shown here :clap::cheers::clap:
 
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Does anyone know if you buy the part 89540-60160 (used) if it needs to be programmed?
At a minimum you would need to do a zero point calibration, I believe. If anything more is needed probably depends on how close the used part is to your VIN. But I'm not an expert in this.
 
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Experiencing the same symptoms on my LC100. @FJRyder would you be willing to help me remotely with diagnosis and repair?
Yes, I can. But I do encourage you to at a minimum take the ECU out, open the metal box (metal tabs that need to be twisted to separate the two metal clam shells) and measure the resistance of the suspected bad component. This is why I included the resistance for people that don't own/have access to an oscilloscope.

A digital multi meter for measuring resistance can be purchased for $20-30 .

Or the other option is to buy and replace the ceramic resonator without actually testing it ($5-6) and see if that fixes it. But its a high risk, low cost option.

Edit: should have also mentioned the option of purchasing the Techstream cable (more info here: this thread ) for $20-30 to be able to get a better understanding of the whole system and if you can communicate with the ECU.
 
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Yes, I can. But I do encourage you to at a minimum take the ECU out, open the metal box (metal tabs that need to be twisted to separate the two metal clam shells) and measure the resistance of the suspected bad component. This is why I included the resistance for people that don't own/have access to an oscilloscope.

A digital multi meter for measuring resistance can be purchased for $20-30 .

Or the other option is to buy and replace the ceramic resonator without actually testing it ($5-6) and see if that fixes it. But its a high risk, low cost option.

Edit: should have also mentioned the option of purchasing the Techstream cable (more info here: this thread ) for $20-30 to be able to get a better understanding of the whole system and if you can communicate with the ECU.
I appreciate that. Hopefully I don’t have to get your help. When I last scanned the vehicle using Techstream I was able to read the ECU and did not find any error codes. I just dropped off the vehicle at RPM Garage in Monrovia so it is now in the hands of the capable team there. Hopefully it’s something else like a sensor or cable - will post back with their diagnosis.
 
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A few obervation and tips. I had the EXACT same symptoms as described by the OP. If you can read codes or get techstream to communicate with your ABS ECU more than likely you have another problem. There is no need for Techstream or any other communication to get a used eBay version of this part to work. It is plug and play.

I sent my bad unit to a buddy that designs circuit boards for a living to remove and replace the chip listed above. He is much better suited than I to so.:)

Finally, when removing and installing the silver box the nuts (10mm), especially the top one will fall off and go behind the dead pedal or the carpet - which makes recovery difficult. I had a stash of extras so it was not a problem. When reinstalling get the top nut on first. For me this require the right length extension and the use of blue painters tape tripled up on an 11mm socket to keep the nut from falling out while starting the threading process.

A big shout out to FJRyder for figuring this out and posting. Without his posting I would have never figured this out.
 

Slashzero

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The symptoms:
Recently, I had my 2002 LX470 experience the following condition; ABS, TRAC, VSC TRAC, VSC OFF, and break lights all came on.
My 2003 LC had this start happening a few days ago. I found this post and was preparing for the worst.

A scan showed it was the speed sensor... what a relief. Anyway, the connector was cleaned up, and reattached, and the code reset. The warning lights haven't come back on, yet. If they do, I am going to replace both sensors and hope for the best.

I would recommend before starting on any repairs, try a scan to see the actual codes.
 
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A big shout out to FJRyder for figuring this out and posting. Without his posting I would have never figured this out.
Ninja, thanks for the shout out! Its not a hard fix at all if you can solder.

The main thing is this is a very specific issue and there are 100s of potential failure points as Slashzero has pointed out. So most of the time is going to be spent in diagnostics. The quickest/easiest way to that, is the Techstream cable in my mind.
 

Slashzero

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My 2003 LC had this start happening a few days ago. I found this post and was preparing for the worst.

A scan showed it was the speed sensor... what a relief. Anyway, the connector was cleaned up, and reattached, and the code reset. The warning lights haven't come back on, yet. If they do, I am going to replace both sensors and hope for the best.

I would recommend before starting on any repairs, try a scan to see the actual codes.
no ABS or Brake. Can’t find my OBDII scan tool either damnit.

well, crap. Took the truck out for errands and a few miles out I got:

CEL, VSC TRAC, VSC OFF

no ABS or Brake. Can’t find my OBDII scan tool either damnit.
 
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20200731_003654.jpg


One thing I was unsure of going into the repair was should it be soldered sideways as done by FJRyder.. what I found was that it definitely has to be soldered exactly as shown due to being smaller it is the only way it will reach across the three contacts
 
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no ABS or Brake. Can’t find my OBDII scan tool either damnit.

well, crap. Took the truck out for errands and a few miles out I got:

CEL, VSC TRAC, VSC OFF

no ABS or Brake. Can’t find my OBDII scan tool either damnit.
You probably have the same issue I have.

20200216_194930.jpg
 

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