ABS Problem—Suggestions appreciated

[Desert Rat]

’98 LC, 60+K miles. Several weeks ago the ABS light came on several times---stop, ignition off, start the engine, ABS OK. Last week it came on and now will not go off.

Using the procedure from the FSM I dumped the ABS codes and got a 25 “Open or short in hydraulic brake booster solenoid circuit (SA1 circuit)” Using the FSM procedure I attempted to clear the code; no luck. Following the FSM I checked the resistance of the SA1 solenoid and found it normal.

I then popped the ABS ECU for inspection and could find no sign of any damage. Following this I measured the resistance of all eight solenoids from the connector to the ECU and chassis ground. All were normal which rules out both opens and shorts.

This vehicle has had a troubled past; it appears it was T-boned on the driver’s side in the vicinity of the fire-wall. (See https://forum.ih8mud.com/showthread.php?t=60664 for details)

The FSM troubleshooting procedure leads to “ECU may be defective.”

Three questions:

1. Any suggestions for other checks I can make?

2. Anyone know of a Junk Yard that might have a salvaged ECU? I would rather not pay the $400 for a new one just to find out the ECU is OK. ECU part# 89540-60080.

3. The Owner’s Manual says it’s OK to continue driving the vehicle and the brakes will work normally---without ABS. But, of course, they add, “get to dealer as soon as possible.” Is there any danger of driving while the ABS is not working? So far the brakes work fine and I doubt I will be needing ABS any time soon.

I have 50 years experience in the Aerospace business and am well versed in troubleshooting Electronic/Electrical systems so I think I know what I am doing. But this is my first Toyota and I suspect others out there have much better knowledge of this system than I do. Therefore my call for help from this ‘vast storehouse of knowledge’.

 

[LEXUSBEN]

First off - driving with the abs light on will not hurt anything, you just don't have abs. Braking system will operate normally like a car without abs.

One last thing I would try before you condemn the ecu. The two junction block connectors on the drivers and passenger side kick panels. To access you have to remove the plastic trim and you will see a fairly large connector with a 10mm bolt in the middle. Sorry no pics. Has about 75-100 wires all the same color going into it. Unplug it and blow, with compressed air, the connector and the part where it plugs in (junction block) thoroughly. Do this for passenger and drivers sides. Have had many problems with metal slivers from manufacturing causing all kinds of problems. Questions, let me know.

ben

 

[Desert Rat]

Thanks Ben for your suggestion. I have read of the connector contamination problem, but if the Factory Wiring Diagrams are correct, the ABS wiring goes directly from the ABS ECU to the pump/solenoid assembly bypassing the Junction Blocks. So this probably is not the source of my problem. But, when the hot weather abates here I should probably follow your recommendations just as “preventive medicine”.

I do think I need a test ECU to determine if that device is the source of the problem and was hoping someone might point me to where I might find a salvaged one.