Hey all,
I found the post below quite useful as I am having the EXACT same symptoms. The only issue I am running into is how to open up the Skid ECU case to get at the circuit board. Does anyone have any experience opening the metal case, or another way to get the circuit board out? Winter is coming to Montana this weekend, and I would really like to have my ABS back!!
I found the post below quite useful as I am having the EXACT same symptoms. The only issue I am running into is how to open up the Skid ECU case to get at the circuit board. Does anyone have any experience opening the metal case, or another way to get the circuit board out? Winter is coming to Montana this weekend, and I would really like to have my ABS back!!
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.
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.
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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.
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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.
View attachment 1895210
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.
Bad part measurements in circuit:
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)
As I mentioned the new part I ordered from Digikey (CSTCR4M00G55B-R0) was physically too small. The important parts are 4MHz and 39pF capacitance. There may be a larger part that is the same as the original but I haven't looked yet.
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
