Rear Steering Rack failure - rebuilt/second hand parts? GS 450h F-sport 2014

[stripester]

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

[WSandME]

I have a '14 F-Sport with DRS. I just watched your video (Thanks!) and I'm dismayed that it appears my steeing is not working - there is no rear-wheel movement when exercising the steering wheel in park, engine running. There are no error codes listed. I checked the 80A link on the Battery and it appears OK. Am I missing something? I'm assuming it needs Techstream to force the movement? How can I check if the DRS on my car is actually working, without techstream? 

[stripester]

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

[WSandME]

Thanks, Paul.

I 3D printed a Go-Pro camera mount to stick to the wheel arch...

... It Verks!

 

 

 

[stripester]

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 😞 

[stripester]

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

[HensTeeth]

Gulp. You're thinking that stripping the rack down to its constituent components should identify the root cause, with a replacement from Amayama as a backup plan?

I'm very interested in how you get on...

[stripester]

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... 

[HensTeeth]

Probably wouldn't be your first choice, but is a conversion to a non-rear steer arrangement feasible, with a rack removal and replacement with tie rods? Mechanically likely to be easier than persuading the computer to let go of its amputated rack, I suspect

[stripester]

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.

[stripester]

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.

 

[stripester]

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.

 

 

 

[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!!

[WSandME]

Paul, Thank you for this Magnum Opus.

I shall endeavour to get under mine and apply some sort of sealant - in other circumstances, I’ve used a Hot Glue gun to good effect.

[JackKone]

On 2/12/2024 at 10:36 AM, stripester said:

DRS now completely fixed, it was the DRS ECU.

Hi, where can I find this DRS ECU? I want to check if I have the same problem that can be fixed with some soldering.

[stripester]

20 hours ago, JackKone said:

Hi, where can I find this DRS ECU? I want to check if I have the same problem that can be fixed with some soldering.

Hi jack, 

My problem wasn't the ECU in the end it was the rack, what's the fault code? 

[cruisermark]

It looks like this problem is surfacing more and more as these cars age

Just seen a 13 plate GS450H for sale £4995 spares or repair

2013 Black Lexus GS 3.5 450h V6 F Sport CVT Euro 5 (s/s) 4dr for sale for £4,995 in Thrapston, Northamptonshire (autotrader.co.uk)

[stripester]

On 8/16/2024 at 7:52 AM, cruisermark said:

It looks like this problem is surfacing more and more as these cars age

Just seen a 13 plate GS450H for sale £4995 spares or repair

2013 Black Lexus GS 3.5 450h V6 F Sport CVT Euro 5 (s/s) 4dr for sale for £4,995 in Thrapston, Northamptonshire (autotrader.co.uk)

Yeap, I am expecting cars around 10 to 12 years old to develop this fault. 

[johnatg]

Probably just as they get too old for potential Lexus warranty!

[cruisermark]

Apparently this one had the rear axle replaced under warranty:

2012 White Lexus GS 3.5 450h V6 F Sport Saloon 4dr Petrol Hybrid CVT Euro 5 (s/s) (345 ps) for sale for £12,850 in GLASGOW, GLASGOW CITY (autotrader.co.uk)

[stripester]

8 hours ago, cruisermark said:

Apparently this one had the rear axle replaced under warranty:

2012 White Lexus GS 3.5 450h V6 F Sport Saloon 4dr Petrol Hybrid CVT Euro 5 (s/s) (345 ps) for sale for £12,850 in GLASGOW, GLASGOW CITY (autotrader.co.uk)

Yeah I've just noticed that.... I bet it's the stroke sensor... You cannot buy the part separately... It's ridiculous at most a £200 sensor.... 

[steve2006]

Obviously this part is being manufactured by someone as a separate bolt on item but to be not available as such is unacceptable, it’s like a head gasket failure, the gaskets are manufactured but not available to purchase, you need a complete new engine.

However this situation however is nothing new, some early LS400s suffered from a clogged mesh filter on the steering rack solenoid. This solenoid was easily removed with a couple of bolts to take out and could then be cleaned and refitted. If the solenoid had failed however this was not available as a separate part and the complete rack required.

Finally another example are the side privacy blind hooks in the LS430, these become brittle, the mounting posts break and they fall off. Held to the door trim by 2 screws ( so completely separate ) they cannot be purchased as such, the complete trim needs to be replaced at a cost exceeding £100.00.

Fortunately having a similar attitude to Paul I repaired my hooks with some Araldite rapid and longer fixing screws.

[steve2006]

Just had another thought ( I know 2 in a day!).

If components on boats can be protected from water and salt ingress why can’t similarly exposed parts on cars have the same level protection?
Another example here are the internal corrosion issues with ride height sensors.

[stripester]

10 hours ago, steve2006 said:

Obviously this part is being manufactured by someone as a separate bolt on item but to be not available as such is unacceptable, it’s like a head gasket failure, the gaskets are manufactured but not available to purchase, you need a complete new engine.

However this situation however is nothing new, some early LS400s suffered from a clogged mesh filter on the steering rack solenoid. This solenoid was easily removed with a couple of bolts to take out and could then be cleaned and refitted. If the solenoid had failed however this was not available as a separate part and the complete rack required.

Finally another example are the side privacy blind hooks in the LS430, these become brittle, the mounting posts break and they fall off. Held to the door trim by 2 screws ( so completely separate ) they cannot be purchased as such, the complete trim needs to be replaced at a cost exceeding £100.00.

Fortunately having a similar attitude to Paul I repaired my hooks with some Araldite rapid and longer fixing screws.

The annoying part is that the part is manufactured by Toyota, based on the part number it's a sub component for the steering rack... Really frustrating. 

[stripester]

9 hours ago, steve2006 said:

Just had another thought ( I know 2 in a day!).

If components on boats can be protected from water and salt ingress why can’t similarly exposed parts on cars have the same level protection?
Another example here are the internal corrosion issues with ride height sensors.

If you have a car with this steering rack I'd encourage anyone to protect the sensor with paint or other maybe plastidip... I've sprayed mine with cavity wax all over...