Lane Departure Assist setting grayed out

What?? The auxiliary battery is never meant to be disconnected. That's your problem there. Now, you need to take the car to the dealer to have the steering-angle neutral point and back-door lock initialized.

INITIALIZATION

PROCEDURES NECESSARY WHEN AUXILIARY BATTERY TERMINAL IS DISCONNECTED/RECONNECTED

NECESSARY PROCEDURE: Memorize steering angle neutral point

EFFECT/INOPERATIVE FUNCTION WHEN NECESSARY PROCEDURES NOT PERFORMED:

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Lane departure alert system (w/ Steering Control)
Intelligent clearance sonar system*1
Simple advanced parking guidance system*1
Pre-collision system
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NECESSARY PROCEDURE: Initialize back door lock

EFFECT/INOPERATIVE FUNCTION WHEN NECESSARY PROCEDURES NOT PERFORMED:

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Power door lock control system
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*1: When performing learning using the Techstream.

NOTICE: After the power switch is turned off, the radio and display receiver assembly records various types of memory and settings. As a result, after turning the power switch off, make sure to wait at least 85 seconds before disconnecting the cable from the negative (-) auxiliary battery terminal. (for Audio and Visual System) After the power switch is turned off, the navigation receiver assembly records various types of memory and settings. As a result, after turning the power switch off, make sure to wait at least 120 seconds before disconnecting the cable from the negative (-) auxiliary battery terminal. (for Navigation System) When the cable has been disconnected and reconnected to the negative (-) auxiliary battery terminal, open and close the fuel lid before turning the power switch on (IG).

HINT: The accuracy of the fuel receive gauge changes depending on fuel tank deformation caused by internal pressure. Before turning the power switch on (IG), equalizing the fuel tank pressure with the ambient air pressure by opening and closing the fuel lid after disconnecting and reconnecting the cable to the negative (-) auxiliary battery terminal increases the accuracy of the fuel receiver gauge.

 

I am not sure what Gokhan is talking about. The 12V battery is not called an auxiliary battery. There is nothing in the owner's manual that that it should not be disconnected other than that the ignition switch should be off first. What the Hell is the "steering angle neutral point"? Back door lock??? There are two back doors and a back hatch. What is he talking about initializing a back door lock? Today is Friday the 13th, not April 1st.

 

The 12 V battery is officially called the auxiliary battery by Toyota in all parts of the world. What I posted is copied and pasted from the official Toyota repair manual.

I probably don't have the sections of the manual where the two initialization procedures (for steering and back-door lock) are discussed.

 

OK, I can accept that even though that is not what my 800+ page owner's manual calls it. What I cannot accept is your statement that if you disconnect it you must then go to the dealer to "memorize your steering angle input" or initialize the lock on the rear hatch. I can just imagine driving to my local Toyota dealer after I have cleaned the 12V battery terminals and asking them to memorize my steering angle input for me.

 

It is not in the 800+-page owner's manual but it is in the 800+-thousand-page repair manual.

I didn't download every section out of tens of thousands of sections, but Toyota doesn't put something in its repair manual unless it is significant. You can subscribe to TIS for a day for about $15 and download the relevant sections for the calibration procedure mentioned along with anything else of interest.

 

While I am aware of the initialization necessary after the 12v battery disconnect, the "Memorize steering angle neutral point" and "Initialize back door lock" are new ones I have not read or heard. The manual does not list them either. Does it really need to be done every time the 12v battery is disconnected? My feeling is that in very rare cases removal of the 12v battery can cause problems in a system that may necessitate such a procedure. It would be crazy if a normal DIYer can not even change the 12v battery without a visit to a dealer. Then again, it is Toyota... maybe that's the way this car is designed.


BTW, the owner's manual for the 2020 PRIME (and presumably for earlier model years as well) does have the term "auxiliary battery". One twice in the same section, but still...

 

I don't have the relevant section of the Toyota Prius Prime OEM repair manual on this, but I've found some information for some Lexus models.

DIY LS430 Steering Wheel Centering/ ZERO STEERING ANGLE POINT - ClubLexus - Lexus Forum Discussion

5) What is Steering Angle Neutral Point?

The steering angle neutral point tells ECM that, according to the driver, the steering wheel in current position will be used for straight driving.

ECM understands when the driver attempts to balance the straight driving during driving, however, it never resets this neutral point as it may create a serious safety condition.

The only exception is when electronics enters learning mode and slightly corrects the VSC behavior to ensure the neutral point remains the same during straight driving. Once the behavior is learnt, it is saved in memory.

If any steering pull is present, it may indicate faulty steering neutral point. However, during very low speed driving, the driver may notice the wheel is centered.

5) How do I obtain Steering Angle Neutral Point?

Lexus service manuals specifies that LS430 enters SYSTEM INITIALIZING mode once the negative battery cable is disconnected for more than 2 seconds.


Important tip: The steering wheel must be centered in advance before coming to a complete stop - to avoid discrepancy, do not center the wheel when the car is already stopped.

During the SYSTEM INITIALIZING mode, the driver must correct the steering angle neutral point using either of the following methods:

- Method 1. Turn the steering wheel to the right and left fully.
- Method 2. Drive the vehicle at more than 20 km/h (12.43 mph) for more than 5 minutes on a straight road and with as little traffic congestion as possible.

While driving at a constant vehicle speed, the ECU recognizes the point where the steering angle changes the least and memorizes it as the steering angle neutral point.

Stop the vehicle and check whether the neutral point is stored or not. If it is not stored, drive the vehicle some more (the neutral point is stored by driving the vehicle straight).

6) Which method do I have to pick to reach the Steering Angle Neutral Point?

Both. First method 1, then method 2.

7) Does the discrepancy of 1,2,3,4 degrees of steering angle sensor cause car instability?

Depends on your car suspension setup / age / mileage. Despite LS430 advanced VSC system, the driver may not even be aware of this condition. This explains why in many times wheel alignment in reputable shop cause such a great comfort. Whenever the systems are in perfect balance, it removes the necessity of additional brake actuator force applied during regular driving, which decrease wandering, pull, hesitations, and unexplainable throttle changes.

That's it for now. Thank you for reading this DIY. Hopefully it helps someone to fix their steering wheel issue. Also, if anyone has additional thoughts on the Steering Angle system, please share them. This topic is poorly covered by LS430 service manual.