Hi all - working through the remaining issues on my very sour 03 RX300. I decided to tackle the ABS/VSC this weekend. It has always acted strangely, engaging at random times under 20mph with seemingly no correspondence with brake, steering, etc.

I hooked it up to techstream and went on a test drive. I noticed some minor deviations in speed sensor readings (left and right, usually under 1mpg difference and infrequently) and thought this might have been the cause, but then realized the steering angle sensor was frozen at something like 1145 degrees (I assume full lock?). Turning the wheel had no impact on this reading, but it stayed constant, and I didn’t experience any errant activation. Then, after about 15 minutes of driving and while executing a slight turn, I noticed the angle sensor snapped to a more believable reading, something like 14 or 15 degrees, and at that moment the VSC kicked in.

No codes were present, but the pattern was consistent - steering angle sensor unfreezes, VSC activates. I’m now assuming this to be the cause.

I plan next to take apart the steering wheel/clockspring area to access the sensor (I assume this would be the right place to look? I’m not finding much in the way of service manuals for this particular issue - have the full set but can’t access right now) and clean contacts, take apart, etc. but, in case that doesn’t work, the OEM part is quite expensive - is there any reason not to scout out a junkyard part? Or perhaps something easier that I’m not thinking of?

Thanks very much for any help.

 

There is a calibration process [you will have to search for that].

When it comes to salvage yard and used sensors ... there is no guarantee that the part you get will be in worse or better condition. I would tend to stay away from them till I am sure that my part is bad. Adding an item of unknown condition in trying to debug is not the right way [unless you are desperate]. I would suggest spend the time in searching and locating but wait till the diagnosis is confirmed.

If the vehicel has missing history, you can count/measure lock-left, lock-right and middle > should be steering straight ahead. If an ammuture has put the steering back they may have it off centered and compensated by tie-rod adjustment.

Salim

 

My dad's rx has similar issue, just VSC throw almost after engine start. Seems I got through allsystems and tests, and only this sensor still not replaced. Probably it is good you did not read manuals, it took me more than year with manuals to get to similar outcome - steering angle sensor. Per manual, sensor should begin considering by system after 24mph, so I did not even think about it, even everything pointing on that sensor, In reality seems it is use data right after starting engine. BTW my dad already bought used sensor, and I'm planning to replace it next weekend. Either way, it would be successfull, or not, I will update my thread on ClubLexus.

 

Updating this thread with a question.

First, turns out the steering wheel sensor reads 1145 degrees until a speed threshold is reached for the first time. This is documented in the service manual. Bizarre to me, but never mind, I’m sure there’s a good reason for it. So the angle sensor is not the culprit.

After a bit more probing I increased the graph scale and noticed a discrepancy in the readings from the front right speed sensor. It appears amplified when compared to the other sensors. See:



The relationship between VSC/ABS engagement and the amplified readings seems solidly correlated in some cases. For example, VSC correlates with a period where all three sensors are measuring speed and the FR hasn’t caught up. Or sometimes it will engage when FR measures a more dramatic change in speed, while the other three show a more gradual increase. But other times I cant pinpoint a relationship between VSC/ABS engagement and the amplified readings.

A friend of mine who is a Toyota mechanic replaced the sensor and I am sure that the air gap, orientation, etc is correct. However, the discrepancy remains, so I suppose it must be a reluctor ring. No obvious faults with the reluctor ring on cursory inspection but might be more apparent on second look. Funny enough the FL ring was rather badly seated but the readings from that sensor seem fine.

My question: is this pattern typical of a defective reluctor ring? Or am I barking up the wrong tree?

Thanks very much for any advice.