stripester

UPDATE JUNE 2024

After having the part on order with two differnt suppliers, I have been informed that the stroke sensor is not available in the open market.

I would suggest that if you have dynamic rear steering that you remove the rack and -

A) protect the stroke senor by encapsulating it in some kind of paint/wax protection.

B) Remove it (if you can) and replace the screws, rubber seal/gasket and replace back in the rack.  Also protect it from the elements as A (NOTE the Stroke Sensor could be damaged trying to remove it).

THE FOLLOWING IS AN IDEA I HAVE, NOT TO BE DUPLICATED ON OPEN ROADS I TAKE NO RESPONSIVILTY IF YOU DO IT!!

I am going to tap into the Motor Reolver outputs and wire them to the Stroke Senor inputs in the ECU to trick the ECU into thinking that the Motor Resolver output is the stroke senor input, this, hopefully this will produce a fully working rack.  I will then have to blank the mounting point where the old Stroke sensor was fixed (using a metal plate, such a a EGR blanking plate).  The obviously omits any position certification / or part falure protection between the sensors, it could be dangerous if the motor resolver fails!!

I have now done a deep dive into the DRS issue I had, I have now replaced my ARS but more importantly identified the failure point and how to fix it,

It’s a long read grab a cuppa and a biscuit...its worth it...

hopefully it will help all Lexus owners with the Aisin rear DRS or ARS as Aisin call it…

Background to Problem

Background, this is important as it plays a part in the failure…..I had a long drive in the car from Manchester to Chester in poor weather conditions about 0 degrees it was raining and cold.  The roads were gritted and snow/frost present.

I parked the car from Thursday to Saturday in an open-air carpark where it was lightly snowing and it froze over the three nights the car was stood.

Due to an Android Auto kit installed in the car it caused the Battery to flatten, on the Monday the car would not start, meaning that I needed to jump start the car….I rang RAC and Lexus and followed the correct procedure to jump the car…I initially thought his had caused damage to the DRS ECU but this was coincidence and not the case as I found our later.

I drove the car home with no problems on The Saturday.  On the Sunday Drove 10 miles local, no issues.  Then  Drove 5 Miles, then had DRS, AFS and VSCR warning light illuminate

The problem

Scanned the Car, these were the fault codes -

     VGRS                    C15C9                 DRS System Malfunction

     AFS                        B241D

     ABS/VSC/TRC  C120E     A malfunction signal is received from the rear steering control ECU for 1 second or more

     C1241    Low Power Supply Voltage Malfunction (Presumed due to the previous Low battery)

The above modules with DTC’s pointed at the DRS ECU containing faults.

I scanned the DRS ECU it had the following fault –

    C1B17 Motor Rotation Angle Mismatch (Stroke Sensor) 

I reset by using the workshop manual calibration using Techstream –

·         PERFORM ACTUATOR CALIBRATION VALUE INITIALIZATION

·         PERFORM NEUTRAL POSITION MEMORIZATION AND MOTOR ROTATION ANGLE SENSOR CALIBRATION.

At this point, I expected the fault to be a damaged DRS ECU as I had jumped the car.  I had investigated how the rack worked, it’s a very robust design and the components are designed to work under harsh conditions, at this point I was convinced it was the ECU as the car ran fine for a while then it came back, I assumed this was due to component failure in the ECU.

Thinking it was the DRS ECU,  I removed it and asked my brother to look at it, what he doesn’t know about electronics isn’t worth knowing.  He took it apart and solder up what he thought could have been dry joints, I installed it back in the car and it all started working again…

Two weeks later same fault…. what could it be??…I reset it as before and it kept coming back, randomly.  It got to the point that it would not reset, UNLESS I hit the rear tyres with a lump hammer (Yes sometimes a big hammer works wonders) I was now thinking that as the rack worked periodically it “Could” be the rack, but I was still convinced that the design of the rack was pretty bullet proof in design.  A brushless Motor, motor resolver and stroke sensor…robust, logical components for sollid DRS system.  Side note - I have had Aisin gearbox’s in cars before, solid and reliable – Namely my Volvo 850R and T-5R.

Just to rule out anything else I replaced the Auxiliary Battery with a Genuine Lexus Battery, the fault still remained.

In April the fault came back, no amount of hitting the tyres would allow me to reset it, the car was due a service so decided to ask Lexus to review the fault and let me have their verdict.  The reason for this is that I wanted to be 100% of the fault before I planned my next move, I basically wanted someone’s second option to confirm it was the Rack.

 Lexus Service & Lexus UK

The car went in at 109k for service and the Service Manager and Technician met me, very apologetic, it was the rack, the cost for the rack was £10k plus fitting, apparently a two hour job (and I can say it is only a two hour job…read on!)

Note that due to the DRS fault the car now failed its Hybird Health Check, it’s covered for 15 years…..

Not happy with this, I spoke to Lexus UK who would go 50% for the rack, as noted by @Damien7579…Still way too expensive….

I was not willing to accept this as an outcome, time to get my hands dirty....

Replacement Rack

I wanted to repair the rack, BUT I could not take it off and use the car, so needed to source a rack, I could temporarily fit a none-steering rack from an GS F if I could not get a rack…..

Okay, so  I needed a Rack….a few options presented themselves –

Rack from a LS500, or LC500 these are both the same in operation but I would need to replace the inner tie rods with the ones from my failed rack along with the mounting brackets.  I had sourced a LC500 rack from the US about £1500 including import, this was an option.

Used rack from a GS F-Sport….. these are like gold dust…none for sale anywhere. However, the world is a large place, time for “out of box” thinking…

After looking though various Japanese car part websites, I managed to source a rack from Japan, second hand from the “Be-Forward” website.  Some poor reviews on Trustpilot but many looked like they were made up.  I conversed with them over Whatapp and their website, used my Visa card for payment (Credit cards provide insurance) and ordered it, £600 later and 10 days it turned up!

So now I had a rack…

Fitting

I decided to fit the rack myself, I’ve lots of experience with cars at a hobby / enthusiast level, it didn’t look too hard…

I took the diffuser off the car unconnected the Actuator from the ECU and commence operation, watch out for the little studs that held the diffuser on, they like to hurt you! -

Before I started any work, I sprayed the track rod adjustments with WD40 and the location of the Bolts that hold the rack to the Subframe.  I took photos of the track rod threads (And everything else I thought would be helpful) so I could get the wheels roughly pointing forward…IE Get the “Toe” as close as possible.

View without diffuser...

Bolts that hold on Actuator in Blue --

Soak these though with WD40 a couple of days before on both sides, they will be stiff...

I decided to replace the rack without taking the wheels off (Yes it can be done), I drove to car into two blocks of think wood so give me some more space below the vehicle. I firstly unbolted the rack from the subframe, it stays in place as it’s held in by the track rods.  I then started to slowly undo the track rods.  The idea was that I would be left with the track rods connected to the wheels so I could simply screw the new rack onto them, this worked well.  You have to be careful that the wheels stay pointing forward and take up any of the track rod movement by moving the actuator back above the exhaust, The actuator weights about 15kg once the track rods and free you can rest the actuator on the exhaust and then slowly remove it from the vehicle.

Track Rod ends ready to recieve new actuator...

New V's Old Actuator

Actuator removed ready for new one...

Fitting the actutor is in the reverse of removal I started at 7am and was done for 11am with a couple of tea breaks!

New rack in place..

Proof of the Pudding

Okay, now the actuator was fitted time to see if it works, I lifted the rear wheels off the ground using the Diff as per repair manual and -

·         PERFORM ACTUATOR CALIBRATION VALUE INITIALIZATION

·         PERFORM NEUTRAL POSITION MEMORIZATION AND MOTOR ROTATION ANGLE SENSOR CALIBRATION.

It took three attempt and it worked on the last one, I think the reasons for this is the DRS ECU can only calibrate in small steps and had the previous rack setting stored, I am 99% sure this is why the Repair manual says 3 times.

I replaced the rack on 18^th May its now the 27^th May and no faults 😊.

Post mortem of Old rack

This is where it gets interesting!

I now had the old rack, I wanted to see what when wrong, and more importantly if it can be repaired.  I know from the wiring and repair manual how the rack worked.  I  had previosuly measured all the Ohm resistances at the connector, and all were within spec. 

I was convinced that when I was hitting the wheels with a hammer it was dislodging material/debris somewhere.  I noted that the schematic for the New LC500 was slightly different from the GS and it showed the Stroke Sensor as external to the rack, this corresponded to what I had identified as the stoke sensor.  I decided to examine this.  I attempted to remove the stroke sensor from rack, I managed to remove one screw, I stripped the head off the other so ended up drilling the head off, it was then I noticed that where the two screws pass through the stroke sensor the bracket has fatigue cracks and one side had failed, this wasn’t the main cause of the failure, which I will discuss shortly.  What I did notice was the use of stainless-steel screws…these will react with the aluminium over time.

Stoke sensor.

I removed the stroke sensor sensor circled in Blue below -

and looked inside the rack where it made contact with the worm drive, no debris and the worm drive/cog was perfect…

The stroke sensor itself is in two parts, these are screwed together, again with Stainless Steel Screws, these had reacted with the Aluminium and I could not remove them, I examined these locations and again saw fatigue cracks in the casings one side had failed. Since I considered the part was broken I decided to force them apart. When I did, between these parts is a small rubber gasket, definitely NOT up to the job of keeping moisture out, this in my opinion is a poor design, there should be a complete gasket between both.  This design has allowed water to penetrate between them and the constant attacked of moisture and freezing has forced the case apart causing water ingress inside the senor, I have said before, the design is pretty “Bomb Proof” BUT this slight oversight has caused the failure.

Removed stroke sensor - Red=Broken Bracket, Blue=Gap between both casings, Green=You can see the fatigue crack here

Better View of broken mounting to stroke sensor casing due to fatigue and probalby interation between different materials.

After I broke the casing open -

Inside the Stroke sensor, bandy damaged by corrosion and water ingress...

Sensor full of debris and corrosion...causing the readings to fluctuate out of spec

I am now trying to source a stroke sensor and expect this to be a complete repair for the rack, before I fit it, I will be upgrading the interfaces  and inserting gaskets.  I have made contact with Aisin and expecting a call back for their technical chap., I may even decide to repair the current stroke sensor.

I am frustrated that I fitted the new rack with this issue present, I may removed the rack and rectify the defect, OR just spray the Stroke Senor area with protection, such as paint or plastidip....The rack was from Japan and looks amlost like new so not concernded for the time being...

Conclusion

Remember at the start, when I said the car has stood in freezing conditons?? I am sure that was the start of the END for the Stroke Senor due to the freezing conditons driving the casing apart letting more moisture in. 

I hope this helps someone who finds themselves in the same position as me, I will report back if I get the stroke sensor, I am confident that the stroke sensor was the problem looking at the corrosion inside of it.

As a side note, and not to scare anyone, but these rear ARS AISIN racks seem to fail....alot....

Lexus Stockport had to replace one under wartnetty for another GS 450h owner, also the specialist(s) I spoke to had two customers with the identical fault to me, they both got rid of the cars due to the costs, this to me means it's not IF it goes wrong, its WHEN.

Hi HensTeeth,  

That was actually my second thought!!, Sppke to Lexus and a Specialist about "Coding it out" they both said no, as its a "Saftey" system (not sure why) they would be liable if the car killed anyone.  I tested all the connectors to the rack this weekend and are all within the "Ohm" specifications, I guess I just need to wait for the second hand rack to turn up and plan the next move from there, as it happens looks pretty easy to take off and reinstall (fingers crossed)!

Another options is to buy a second hand rack for an LC500 or LS500 (availible in the US) and adapt them to fit the GS, IE take off mounting backets and inner track rods and swap over from my GS, the connectors and wiring seems to to be identical.

That's the idea, I've managed to source one from Japan second hand, so thought I'd try that'd option first... I'll let you know how I get on, totally gutted.... An otherwise ultra dependable car could be written off for a steering rack is just unbelievable... 

Okay, Back for the dealer....£10k for Rack plus fittng, looks like I am getting my hands dirty...

Thats some great footage, thanks for sharing.  Unfortunately my fault is back, in at lexus next week so will bring up the issue, after reviewing all the data logs I've made and Freeze Frame Data it was pointing to the "Stroke" sensor in the Rack, but today the rack started making strage noises and completely stopped working 😞 I am thinking this is going to be expensive 😞 

If there are no error codes, its probably working, you will see it moving when driving slowly, it doesnt move when stopped....

I have the same issue, I'm following this thread and will try to log some data if possible... 

I have uploaded a video to YouTube showing the extent of travel for those who havent see this in action -

DRS in Action using Techstream to force actuator movement

I have exactly the same problem... Don't know why no fault codes... Watching this thread now... 

DRS now completely fixed, it was the DRS ECU.

I looked at the mechanics of the Steering rack, very simple, very robust, would be supprised if this was to fail so assumed it wasn't the failure point.

My orignal fault code was "C1241 Low Power Supply Voltage Malfunction (Presumed due to the previous Low battery) which I replaced, I had to jump start the car at this point.

Then I got a new error C1B17.

On Tis, if the ECU reports "C1B17 Motor Rotation Angle Mismatch (Stroke Sensor)" it says replace the rack, this obviously assumed the ECU is not defective.  This was my original fault after

I noticed on the live data I had no supply perminent 12v supply to the PIG Power Supply, The ECU was reporting 0.46v but should be between 11 and 14v, I measured the Feed and it was 12v, so the ECU was not seeing this.

My Brother who is an electronics genius disassembled the ECU up to a point and noticed lots of "Dry Joints" soldered them up, reinstalled and the ECU was then reporting 12v. BINGO!  Note that the ECU is servicible but lots and lots of pins will need to be desoldered, luckly for me I didn't have to go down this path, note the following link which shows a similar ECU used in the Toyota Camry -

Russian Site with Disassembled ECU

I now needed to test the steering and set the Neutral Position and Calibrate the actuatior (I had previously reset this), note jacking point to do this in picbelow, chock the front wheels!

If you follow the steps in Techstream to memorize neutral and calibrate the rear steering it won't work because Techstream is wrong (or at least my version is 16.00.020), you need to cycle the ignition on and off between steps to presumably put the ECU in programming mode, once done the rear ECU actuated the steering, store the callibration and everything was back to normal. 

I have attached all the information to this post in the event it helps someone.

Usefull Links -

Online Wiring Diagrams

Russian Repair Manual (use translation in browser)

Live Data List Printing(S821-03.pdf WIRING - DRS-RHD-B.pdf DYNAMIC REAR STEERING SYSTEM FREEZE FRAME DATA.pdf DYNAMIC REAR STEERING SYSTEM FAIL SAFE.pdf DYNAMIC REAR STEERING SYSTEM SYSTEM DESCRIPTION.pdf DYNAMIC REAR STEERING SYSTEM TERMINALS OF ECU.pdf

*** UPDATE ***

Reserved for update 

STEERING FIXED NOT RACK BUT DRS ECU

Will updates Sunday 11th

On 10/10/2022 at 5:07 PM, Damien7579 said:

Quick update:

The rear rack was fixed at a total cost of about 4.1k Euro - 1K euro for fitting + ECU and other stuff I had done + 3.1k Euro for the unit itself which included Delivery + VAT + duty.

I ordered the required rear steering part from Amayama Japan and it arrived after a few weeks - I must say their service is incredible! Lexus Galway fitted it no problems and will warranty the work/unit for 12m. The ECU controlling the steering unit had also fried which was another ~2.5K euros (!) but luckily they had one from another customer and sold it to me for 10% of the price.

So, in the end an expensive fix, but the original price was well north of 12k so I think I did well enough to get costs down thanks to this great forum. Cheers to everyone who replied.

Damien

I'm not sure the rack was at fault, I am in the process of fault finding and this is what I am seeing...The ECU is reporting no voltage at PIG but it measures 12v.

Watch this space for the outcome of this....

DYNAMIC REAR STEERING SYSTEM TERMINALS OF ECU.pdf

Live Data List Printing(S821-03.pdf

*** Warning resurecting and old post! ***

DAMN.....Looks like its my turn for this issue, i've scanned the car, tried all the initialisation procdures and all points to a fault with the actuator....In at Lexus in the next few weeks, I will let you know how I get on.

I MIGHT, have a go at disassembeling the unit and rebuilding it....doesnt look a complicated component may just be a motor/bearing issue like the oil pump bearings in the MK3's.

The only way I can stop the engine from shutting off it putting the car in Sport+ and selecting a shift range S1, S2 etc.. When you come to a stop the engine will not shut off (in mine anyway!).  These hybrids don't wear out like conventional start stop cars as the motor smoothly spins the engine up... Not like a starter motor! 

link to online version
 

http://zatonevkredit(blocked word)/repair_manuals/viewdoc_html/AWHoQ8pMU9h2CeTmHHde/AWHoQ8pMU9h2CeTmHHde

Oil is 0w-20 Spec, don't deviate from this its a requirement unless you cannot get it.

It needs to be ILSAC GF-5 or API SN 

PS check the oil every 3000 Miles or so, since its thin it WILL use some!