Hello,
got a late year 2012 RX F-Sport with the active stabilizers on both axles. Now the car has an error on the dashboard pointing to the active stabilizers, and checking the error codes in the system provided:
C193C Front PIG Power Supply Voltage
C1915 Rear PIG Power Supply Voltage
C1920 Open in DC/DC Converter Harness Circuit

Lexus dealership said that both of the computers that are located on the underside of the car, near the rear end, need to be replaced. Of course, both computers don't generally break at once, so it's likely just one of them. But would anyone happen to know if it could also just be corrosion in the connectors? The connectors don't exactly look new.

 

These weatherpack connectors on Toyotas/Lexus nearly never fail, the ones on my 2002 Highlander outlived the frame rails which rusted out. I have only see the connectors for the horn itself fail which are not waterproof-type w/ sealed gasket like the ones of the rest of these cars. I would soak them in hot water to clean up the dirt and disconnect, clean contacts w/ MAF cleaner or contact cleaner and check for power at the pins. You can get access to the wiring diagrams from Toyota TIS (Technical Information Service) with a 2-day subscription. I have done that before and downloaded as much as I could in the 2-day subscription. Totally worth it to get all that service info if you plan to keep the car long term.

It is likely a higher end scan tool can read these computers as well and see if there are any faults in them just like the rest of the modules on the car. That's actually pretty lame of the dealership to not do proper diag on that, as I'm sure they diagnostic software to do so. It seems either they are too lazy to, or want to charge you for both computers.

 

I would wait for a bearable weather day and spend 2 hours on the connectors. Even if the computer module is bad, the connector cleanup is the right first step. Depending on skill, I would de-pin and increase tension, lightly brush and most important grease [for electrical connectors] to prevent further corrosion.

Salim

 

Thanks for the input, fellas.

Indeed, the dealership has their official policy to follow, according to which the solution is to replace both computers for 12500€ here in Finland. Of course knowing what a ridiculous price that is, the Lexus guy recommended to find used computers somewhere. I then took the car to an independent shop, and it was only they who investigated a bit more and took those photos. They told me that they didn't even dare trying to disconnect those cables because based on the look of the connectors, the pins just might snap and be left stuck in the computers. But now I'm just thinking, if the dysfunctional active stabilization system doesn't render the car useless anyway, why not take the risk before sourcing new cables or second-hand computers?

Based on what the dealership told me, it sounded like it's obvious that the problem is in these computers and they did not mention anything about being able to troubleshoot further using their fancy diagnostics tools. Nevertheless, as I don't have the tools nor the facilities to try fixing the problem myself, I can only investigate the error code combination if it could pinpoint the issue. If only one of the computers is broken, why do the error codes point to both of them? A corroded connector that both computers share would make more sense but who knows.

 

Here is an older thread regarding this rare option that may only be on European vehicles, it has photos of the entire active sway bars. https://www.clublexus.com/forums/rx-...r-f-sport.html

Do you notice any difference in how the vehicle drives, handles and steers? I suspect those active stabilizers could be removed and maybe replaced with normal sway bars and you would never notice the difference. The cost to replace those things is more than the car may be worth.
However removing the error message on your screen may be impossible. Ask the independent shop.

 

Looking back, this isn't the first post I've seen about complaints regarding the active sway bars on early pre-facelift RX450h models. Unfortunately I can't give any more knowledge about these as they are a very rare (maybe not even offered) option in NA. I also wonder how the state of the electric motors are in the sway bars, especially if something did end up going wrong with the computer. It seems as though as you've seen, they can work as normal sway bars if the system is ultimately failed/disabled.

Should you want to replace the bars - the rear normal 21mm sway bar is the same for all 10-15 RX450h/350 models, the 16-22 rear one will likely fit too (slightly larger at 22mm), as they share the same mounting points and rear subframe. The front 26mm one is shared with the 2008-2019 Highlander and 2010-2015 RX. Since your car is a 450h, it can be from either a FWD or AWD model as there is no transfer case to clear (AWD models need an AWD front sway bar).

Replacing the front sway bar is a daunting task that I did on my 2002 Highlander AWD and 2008 RX350 AWD. I swapped from the 23mm stock bar on those cars to the 26mm bar that came on the newer 10-15 RX to reduce body roll in corners. It fit, but putting the bar in was a major pain. Toyota calls to drop the subframe, but I was able to squeeze it in on the driver's side by removing a strut, the rear engine mount and steering rack. Definitely a brutal job when you factor in rust. I imagine that job would be easier on a RX450h as there is no transfer case, but likely not worth doing if the bar still functions as it should.

 

Excellent point about the electronic sway bars just acting as normal sway bars if the system fails or is disabled. Given the age of the vehicle and cost to repair, that makes a great argument to just leave them alone and ask the independent shop if there is a way to disable the warning light/code from the now non-functioning bars.

If it was my vehicle that is what I would do.

 

My BMW 545 has active sway bars front and back. Have no idea if they work like the RX450, but I do know how they work on the BMW. It is essentially a motor and pushes against the down force in a turn, to keep the car flat. They produce less understeer making it easier for a novice driver to manage the car in curves. I love them, they work awesome. BMW claims that should they fail, they default to a normal sway bar. If this is in fact true, then there is no need to replace them with factory non-active sway bars. just leave them and dont fix them. I think a good failure mode would be in the event that the motor fails, and the fluid is intact/not leaking out. Another benefit of them is when riding down the road when going straight, you get a smoother ride from the car. That is why my B8's dont feel overly stiff in that situation.

From the technical training manual:

Dynamic Drive has two active stabilizer bars which have a positive effect on the roll tilt angle and handling.
Split stabilizer bars on the axles act as the basis of the Dynamic Drive. The halves of the stabilizer bars are joined by way of a hydraulic oscillating motor. One half of the stabilizer bar is connected to the oscillating motor shaft while the other is connected to the oscillating motor housing. When you are driving straight ahead, the system improves suspension comfort because the stabilizer bar halves are non-interacting and therefore do not harden the basic suspension when suspension is used on one side.

The failsafe valve (safety valve) is electrically actuated. The failsafe valve responds in the event of a power-supply failure or an identified fault in the system. The failsafe valve shuts off the front-axle oscillating motor when de-energized. Thus the active stabilizer bar behaves like a normal mechanical stabilizer bar and brings about understeering.

 

We have a 2006 650i with the active sway bars as well. I love how they help keep such a heavy car like that (6er convertible weighs 4300 lbs!) nearly flat in corners. May need to reseal them though as they have a small leak. Even with KW V3 coilovers set to stiff still rides great (Better than our '14 RX, but not as good as the '08 despite it being on Eibach springs and bigger sway bars). What I don't like is the active steering. Having the rack's ratio change while at different speeds does not feel natural. How do you like your M6? I've been contemplating swapping to the M5/M6 rack and pump on our 6er to get rid of the active steering.

 

I have both steering systems 545/M6. I personally prefer active steering. My E60 practically drives itself because of it, but is still very engaging. M6 is too loose for me, but, I've read it can be adjusted for a tighter feel. Something I wish our RX 350 had running at high way speeds.

I'm curious if the OP feels he is losing any stability with his sway bar system not working as intended. Is it now behaving like a normal sway bar system?