Lexus GS 450h Sport Radar Cruise Control Retrofit

[Lexusls400 =)]

I thought I'd start a new thread for this as it's something I've been pondering doing for some time. Only recently have I been able to pull together enough information and parts to have a proper stab at this job.

Significant credit should go to forum member Britprius as it was his thread on this subject that inspired me to go ahead. 

I was also inspired by a similar thread on ClubLexus where someone managed to retrofit the system to a ~2011 GX460 (Not without difficulty), a newer car with even more systems to contend with, but also not too dissimilar in terms of wiring and radar cruise system. https://www.clublexus.com/forums/gx-2nd-gen-2010-present/921818-retrofit-oem-radar-cruise.html

My car is a 2008 GS 450h Sport (with the active stabiliser system)

Information that leads me to believe this job is economically viable:

• The majority of the wiring harness is already in place. This was confirmed by studying the wiring diagram. Extract showing main cruise components below:
  • All wiring appears to be present, apart from the 5 cable section between the millimeter wave radar sensor and 'BA2'. BA2 is in the main engine room fuse box and sure engough there are spaces in the connector for the 5 missing cables. These cables simply need to be run from the connector out to the radar sensor in front of the radiator.
• The 'Distance Control ECU' (radar cruise computer) is essentially plug and play. There is a bracket ready for it under the steering column and the harness with correct plug preinstalled is simply taped up ready to be connected.
  • The ECU has 2 possible part numbers: 

    01	88240A	88240-30460	01	02.2006 - 09.2007	COMPUTER ASSY, DISTANCE CONTROL	GWS191..RHD PRECRASH SYSTEM-WITHOUT(DRIVER ASSIST BRAKE)
    02	88240A	88240-30461	01	09.2007	COMPUTER ASSY, DISTANCE CONTROL	GWS191..RHD PRECRASH SYSTEM-MILLI-WAVE RADAR TYPE

  • The first one is easier to get hold of cheaply (20-30GBP)and is from the pre-facelift cars. I will try this first, although my car is a post-facelift car.
• The 'clock spring' in the steering wheel is the same across models and so has the additional wiring for radar cruise functions.
  • A new cruise control stalk is required (part 84632-58011)
    , with the extra forward movement controlling switching between radar and normal modes. This is presumably not required to get the radar working as according to the manual the car will default to radar cruise after each ignition cycle. This is the 'Mode' switch on the wiring diagram above.
  • This stalk needs a different wire from stalk to the clock spring. Part number 

    84633-48010

    01

    09.2007

    WIRE, CRUISE CONTROL SWITCH

    GWS191 PRECRASH SYSTEM-MILLI-WAVE RADAR TYPE

  • The distance control toggle switch is required in order to change the radar distance (short, medium & long). This is the 'dist' switch on wiring diagram above and is integrated with the right hand button pad of the steering wheel.
  • Both of these switches should not be essential in order to initially test the system, but they can be acquired new or from a breaker. May be cheaper to buy a steering wheel with the switches installed and just swap them over to the existing wheel. Alternatively Britprius alluded to the possibility of coming up with some DIy solution since both of these functions seem to be simple switches grounding a wire.
• All the other significant ECUs seem to share part numbers between active cruise and normal cruise models as far as I can tell.. (Browsing through Amayama parts catalogue)
• The Millimeter wave radar sensor is available from breakers. Part numbers: (Check out the new price!)

• 01	88211B	88210-30080	01	02.2006 - 09.2007	SENSOR ASSY, MILLIMETER WAVE RADAR	GWS191 PRECRASH SYSTEM-WITHOUT(DRIVER ASSIST BRAKE)	4,309.13 USD
  02	88211B	88210-30190	01	09.2007	SENSOR ASSY, MILLIMETER WAVE RADAR	GWS191 PRECRASH SYSTEM-MILLI-WAVE RADAR TYPE

 

So to summarise, I should only need the follwing

• Distance control ECU
• Radar sensor
• New switches for steering wheel
• Appropriate hardware to mount above items
• Wire and connectors for missing section of harness
• New Grille/badge suitable for radar (Currently not sure on this)

 

More to follow...

[Lexusls400 =)]

Part 2: What I've done so far..

 

I bought the following:

• Distance Control ECU 88240-30460 (£20 ebay)
• Millimeter wave radar 88210-30080 (£90 ebay)

I installed the ECU under the steering column. Removed 2 screws holding trim panel below knee airbag, allowing access to the waiting connector. Easy enough.

I then connected techstream via my cheap mini VCI cable and voilla, it showed radar cruise as a module! I can see the radar cruise initialisation and calibration programs available in the utility list, but when I try to load the data list I get a communication error. This happens to be the same error I get when trying to access hybrid control module, which is a bit of a bummer. I suspect this cable is no good, as I wanted to access the hybrid control module previously to check the hybrid systems and had no luck. I'm assuming that the distance control ecu is maybe dependant on hybrid control... maybe.

 

Anyway, I have ordered a (hopefully) better cable as I need to get techstream reliably working to stand any chance. I went for the VXDIAG vcx nano and am waiting for it to be delivered.

Next job while waiting was to wire up the radar sensor to the unused pins in the fuse box to see if there was any evidence of life. To do this I dismantled an old PCI Express connector and soldered the crimped wires to some lengths of random wire I had laying around, soldering this in turn to the wire tails coming out of the radar sensor (fortunately this came with original connector plug in place). This is by no means the finihsed product, just a quick and dirty way to establish if I'm on the right track.

 

Before connecting anything to the fuse box I probed the pins to make sure grounds and lives matched up with what was expected according to the wiring diagram. All seems well.

Next step was to shove my jerry rigged wire harness into the appropriate holes in the plug, taking care to follow wiring diagram. Once satisfied everything was in the correct order I turned the ignition on and set cruise control switch to ON and...

Hurrah!! Radar Ready is displayed. This was very encouraging and evidence that at least some systems were talking to each other.

TBC

[Herbie]

Excellent job and write-up Ollie, I eagerly await the next instalment  

[Lexusls400 =)]

Part 3: Significant Progress

 

I finally returned home from 5 weeks of work (I work at sea) just before Christmas. Awaiting me was a small pile of self-bought presents relating to this project.

I previously ordered and received the following:

·       Entire steering wheel complete with radar cruise specific cruise stalk and distance control flap, in the 2008 facelift style. This was around 60GBP from a Lithuanian scrapyard.

·       VXDiag VCI Nano Toyota Techstream cable. Purchased from VXDiag online shop.

·       Thin Wall Automotive Cable 0.75mm 14.0 amps. 2m lengths in 5 colours: brown, blue, red, dark green and light green. 2.50GBP total.

·       Heatshrink Sleeving 2.4mm 2-1 shrink ratio. 1m @ 0.5GBP.

·       Convoluted Sleeving 6.6mm i/d Nylon. This should match closely the stock wiring harness look. 2m @ 1.20GBP. All of the above purchased from IEM Supplies.

·       Female crimp connectors from AliExpress. Smallest quantity available was 100 for around 15GBP. Not ideal, but I wanted the proper connector as the previous PCI-Express connectors were not fitting properly.

·       Bolts 90119-06782 x3 for fixing the Millimeter Wave radar transceiver bracket to the existing mounting points. 3GBP from Amayama

·       Nuts 94151-80600 x2 for fixing the Distance Control ECU to the standoffs. 2GBP Amayama

At the end of the previous post I showed a picture where Radar Ready was displayed on the dashboard display after connecting the radar. I went on the temporarily fix the unit in place so I could road test it and see what happened. As soon as I accelerated past approx. 25mph I would get a warning buzzer and the message ‘CHECK CRUISE SYSTEM’ would display. At this point no cruise control, radar or basic would function.

Using my old Techstream cable I scanned the car for fault codes and sure enough several had been triggered by this event.

Of the codes, U0235 seemed the most relevant and means communication to the radar sensor has been lost. This code was generated by both Hybrid Control and Radar Cruise systems, which further confirms my assumption that they are closely linked. Unfortunately, at the time, I was unable to access the live data from either of these modules with my cable to diagnose further. I was able to clear the codes, but they would reappear as soon as I went above 25mph. I thought maybe my DIY harness was out of spec or perhaps a different ‘calibration file’ would be required.

At this point I went away to work and so any further experimentation was postponed. I did however have some time to do more research.

I found the excellent website ‘Toyota Workshop Manuals’ and began searching through the vast, but not easily navigable information available. Widening my investigation to more common Toyota models from a similar era (2005-10) I came across the following relating to the Laser Cruise Control system in 2006 Toyota Avalon, with 3.5l 2GR-FE engine:

“Laser Cruise Flag (L/C Option Flag) Setting Procedure

1. Connect TIS Techstream to DLC3 and turn the power ON.

2. Operate by following the screen menus and select "DATA LIST" from the Laser Cruise Menu and then press "ENTER".

3. Review the Data List setting for "L/C OPTION FLAG".

4. If the "L/C OPTION FLAG" is set to "YES", please proceed to the Adjustment Procedure.

5. If the "L/C OPTION FLAG" is set to "NO", perform the following option selection procedure:

- Turn the ignition switch to the "ON" position.

- Turn the cruise control switch to the "ON" position.

- Depress, and hold, the brake pedal.

- Cycle the cruise control switch to the "Resume/Accel" position 3 times within 3 seconds.

HINT: A beep sound should be heard from the vehicle when the L/C Option Flag selection has been performed correctly.

6. Once the L/C Option Flag selection has been performed correctly, verify the Data List display shows the "L/C OPTION FLAG" set to "YES".

NOTE:

- If the L/C Option Flag is NOT set to "YES" in the Data List after performing the L/C Option Flag selection procedure and the beep is heard,

perform the "INITIALIZATION" option from the "LASER CRUISE" menu on TIS Techstream.

- Once TIS Techstream has completed the initialization procedure, perform the L/C Option Flag selection procedure again as indicated above.

I was unaware of there being an ‘option flag’ for the dynamic cruise system before, and it seems the flag can be set without even using Techstream by following the procedure above. This flag not being set might explain the Christmas tree of warnings displayed when the system tried to activate. Of course, this was for a different model car and also for a laser based system instead of the more modern radar system in the Lexus GS. However, I thought there might be a good chance that this procedure or something very similar existed for the GS.

Anyway, back to the near present. After wasting a couple of hours getting frustrated trying to install the drivers for the VXDiag Nano cable on my laptop I finally got it working by using a Windows 7 Virtual Machine in VirtualBox and using all the software bundled on the supplied CD. I wont go into this process but if anyone needs guidance on this then I’m sure I can help.

After connecting to my car, Techstream identified the model correctly, and I was able to select option code ‘Radar cruise’ and the appropriate model year. I was now finally able to access the live data on the Hybrid Control and Radar Cruise modules. Hurrah!

Note that this screenshot was taken with the radar sensor disconnected. Only change from stock was the Distance Control ECU having been plugged in above the driver’s footwell.

The first thing that jumped out at me was the ‘L/C Option Flag’ parameter that I mentioned above. This was very encouraging, and I could now see a potentially clear path to success.

I decided to fit the new steering wheel controls first as I thought this would be straightforward. I started by disconnecting 12v Battery and waiting 10 mins before exposing the airbag retaining bolts behind 2 panels in the rear plastic cowl of the wheel. These were Torx T30 IIRC and are self-retaining. The airbag assembly can then be carefully pulled away from the wheel. Two connectors on the rear can then be removed and the airbag carefully placed aside, face up. 

The 2 white plugs that connect the steering wheel controls to the clock spring can now be unplugged, but the black airbag connector can be left untouched. The wires are secured to the metal wheel frame by several plastic hooks and they can easily be removed. I took several photos so I could reassemble it exactly as I found it.

The cruise control stalk is held in with 2 screws and is easy to remove by feeding the stalk into the wheel. The 2 control pads seemed like they would be easy too, with one screw securing each side. Unfortunately, it turns out they are also secured on the rear by 2 brittle looking plastic clips. At this point I thought it would be easier just to swap the whole wheel over. After removing the steering rack nut and pulling, twisting, encouraging the wheel and seeing no movement whatsoever (and not wanting to go out and buy the appropriate bearing puller), I decided to go back to plan A.

It turned out that you can pry the rear plastic cowl back just enough to get a slim screwdriver in behind the buttons and release the clips. This was rather fiddly as I was worried about breaking the plastic clips, but I managed in the end. Picture below:

After removing all switch units from my existing wheel and the scrap wheel:

Note the radar cruise stalk has blue tubing on the cable and 3 wires into the plug, compared with the normal stalk’s black tubing and 2 wires.

It was now a simple process of carefully reassembling my original wheel with the new electronics and routing the cables as per the photos I took. Final step is to reinstall the airbag, paying close attention to its wires to ensure they aren’t pinched etc.

 

Once everything was back together, I opened up the Live Data section of the Radar Cruise module in Techstream and checked the new buttons were being registered. Everything looked perfect and the other functions were working properly too.

Creating New Wiring Harness For Radar Sensor

Next step was to make the final version of the missing wiring harness from the actual radar sensor behind the grille and the main engine fusebox. I was fortunate that my radar sensor came with the original connector plug still inserted with a few inches of wire for me to solder to. Obviously without this you would need to procure the appropriate connector, which is a weathertight design.

I simply soldered my new colour coordinated automotive grade thinwall cable to the existing wire tails from the connector plug and covered each joint with heatshrink tubing. These 5 wires were then run into the plastic conduit and the final product was around 2m in length.

 

I mounted the radar sensor and ran the new harness along the route of the existing wire harness (just in front of the top of the radiator), securing with cable ties and feeding through a gap behind the headlight assembly into the area in front of the fuse box. I then (carefully!) drilled a hole in the side of the fuse box and fed the cable up into the top section of the box. Cutting the whole thing to length, it was now time to apply the female crimp connectors to each of the 5 strands of wire. I already had a crimping tool for this fortunately, from another hobby (RC planes).

The wires were then inserted into the vacant holes on plug BA2 as per the wiring diagram below (the plug is helpfully labelled with the numbers making alignment trivial):

 

After a bit of tidying up with electrical tape and a dab of silicone around the new hole in the fuse box, the job was done.

 

Tidying up

I used the new nuts and bolts to secure the radar sensor and the Distance Control ECU in their new locations. To be safe, I checked the new harness with a multimeter to ensure 12v and ground were where they should be.

[Lexusls400 =)]

PART 4: Software and test run

 

I turned on the car, switched cruise control on and once again was greeted by ‘RADAR READY’ message. This appears to be the limit of functionality before enabling the ‘L/C Option Flag’. Therefore, I fired up Techstream and loaded the live data section of the radar cruise control module. L/C flag was still set to NO.

I now attempted to follow the procedure detailed above to set the laser cruise flag. Basically, ignition on, cruise master on, foot on brake and then flick the cruise stick up to ‘res’ and release 3 times within 3 seconds. Alas, nothing happened. Disheartened, I tried again, and again, and again, restarting the car a few times in the process. I was about to give up, but after a bout of ‘button bashing’ I was surprised to hear several rapid buzzer tones from the dash and the below appearing on the screen:

 

Referring to the laptop screen, Techstream now showed the L/C option flag had changed to YES!

I’m not entirely sure what I did differently to make it work, but I would suggest persevering, it should work eventually! After this, I was able to run the ‘initialise’ utility in Techstream, which completed successfully. Then I selected the beam axis adjustment utility:

Low and behold, the sensor appears to be detecting something (it’s roughly 6m from my garage). I held a piece of tin foil against the Lexus badge to check if this was just some coincidence and electrical noise, but low and behold, the range went to zero with tin foil applied.

Obviously the point of this program is to calibrate the aiming of the sensor, using a Special Service Tool from Toyota which is essentially a small pyramid shaped radar reflector on a stand, and following a procedure involving using plumb lines and measuring tapes to establish the centreline of the vehicle. Once the reflector is positioned correctly the aim is to use 3 adjustment screws on the sensor bracket to aim the sensor as described, using Techstream as a sort of aiming scope.

I do intend to come up with some DIY reflector, but for now I can see it is pointing in roughly the correct direction and see no reason why it can’t be tested.

An additional point is the front Lexus emblem. The ‘radar compatible’ one seems to be pretty hard to find and new it is a ridiculous price. After comparing part numbers across many sites however, I think my car may already be compatible. So, I intend to leave the badge for now and see if it works regardless.

Test Drive

After restarting the car, I switched CC master switch on and tested all the buttons. When I pull the distance control flap on the RH side of the steering wheel a little icon of a car appears with 1,2 or 3 lines ahead of it, signifying the set following distance. This flap simply cycles through these short, medium and long distances.

When the cruise stalk is pushed away from the driver and held for a couple of second the radar cruise is disabled and ‘NORM’ displayed instead of ‘RADAR READY’. Now the system simply acts like a normal cruise control, with one small difference from before, the set speed is displayed in top right of the display. Handy.

I set off on the test drive on a quiet road, enabled the system and accelerated past 25mph.. No alarms unlike last time! I set the speed and it worked as expected. I was a little concerned that the radar might be so far out of alignment that it might pick up on parked cars or other objects and apply the brakes, but I had no such problems.

Feeling more confident, I ventured onto a busier road and found a slower car to approach. Setting the cruise behind the other car, I increased the set speed up to a greater speed, but my car simply stayed following the car in front! IT WORKS!!!

Driving around for a good while the system performed flawlessly, accelerating and decelerating as required to maintain the set gap to vehicle in front. Changing distance setpoint worked as expected, and this is not a set distance, but instead proportional to speed.

The system even applies the brakes automatically if necessary (although, as stated in the manual, not full power breaking, maybe 25% or so) If deceleration required is greater than what the system can provide a warning buzzer sounds. Also, if you decelerate below approx. 25mph the system disengages, so you can’t use this in stop/start traffic like more modern systems.

I thought I might experience some warnings due to not fitting components of the pre-crash system, but so far nothing has popped up, even when the car warns of collision due to higher approach speed. I think this may be due to me choosing radar sensor and Distance Control ECU described as "PRECRASH SYSTEM-WITHOUT(DRIVER ASSIST BRAKE)". But then again, perhaps the newer part numbers would also work?

So, in conclusion, this mod is working great right now. I’m not sure I even need to bother building a calibration rig as I’ve not experienced any loss of tracking etc yet. We shall see.

 I'm happy to have unlocked this functionality which has effectively been lying dormant since the car was built in 2008. Now I'm sure it's a pretty rare beast, being a Sport with the Active Stabiliser System and the Dynamic Cruise!

Thanks for reading.

 

 

Edited December 28, 2021 by Lexusls400 =)
Added more information

[KayCee]

Ollie

very well done Shows with perseverance anyhing can be achieved

Good on you

[Herbie]

Wow, that's brilliant Ollie, well done mate. An excellent write-up and a great project.

[Sami Tilander]

Thanx Ollie! I followed your instructions and I've also now adaptive cruise control! Awesome!

Couple of details from my installation:

1. I did not have the connector for the radar, so I had to buy it. The part number for the housing is 90980-12292 and the terminals 82998-24250.

2. Part number for the terminals in the other end of the wire: 82998-12690 

3. I used 0.75mm² wire which was too thick for the terminals. Maybe 0.5mm² wire would be better...

4. to set the L/C Flag to Yes, I had to first execute the Initialization for the Laser Cruise using TechStream and then follow the sequence mentioned above.

5. I made a radar reflector from a thin (1mm) aluminium sheet (and tested the beam adjustment using TechStream):

BR. Sami

[Lexusls400 =)]

 @Sami TilanderThat's fantastic! Made my day knowing it's been useful to another owner. 👍

Some great recommendations and clarification for anyone else following along, too. 

How have you found using the adaptive cruise? Personally, I love it and use it on all kinds of roads. 

Did you need to make much adjustment of the beam axis? I still haven't got around to doing mine, but I'm yet to have a 'false detection' of another car as far as I'm aware.

[Sami Tilander]

I absolutely love it! I've been testing it on different roads and it works like a charm. I was a bit surprised how heavily it actually brakes.

I haven't yet done any adjustments, just checked the the current aiming: the beam axis was only 0.9 degrees on left-side, so it was pretty well aligned (and actually I didn't find a proper tool to adjust the radar: I've the older model which seems to require a 3mm hexagonal socket, which I don't have...).

May I ask from where you have found that new steering wheel? I've been searching for that exact same model (black leather with smaller buttons) for almost 2 months now, but haven't found any...

BR. Sami

[Lexusls400 =)]

Yes, the first time feeling the car brake for itself is pretty unnerving. I found it very satisfying to know that feature had been sat waiting be unlocked for 13 years! If it breaks really hard you even get a 'collision warning' alarm.

To be honest, the wheel is what I had most trouble with too. I just set a saved search for 'Lexus GS steering wheel' on eBay and would check every few days for new listings. I only ever came across one unfortunately. Another will surely come along at some point.. You could also try contacting some of the breakers directly if you see it's a facelift car. Unfortunately not that many seem to have been supplied with the radar cruise kit after 2008 so the wheel is a bit of a unicorn find. I guess you're using a pre-facelift wheel?

[Sami Tilander]

Actually I've not done anything for the steering wheel yet. The system goes to the radar mode and long distance, as those have been enough for me so far. I bought a pre-facelift wheel, but I don't have airbag for it (I cannot use my airbag as the cover is different), so I probably just utilize the control stalk from it and try to cope without that distance selection button. Have you ever switched back to the normal mode? In any conditions?

BR. Sami

[Sami Tilander]

Small update on this: I finally managed to sort out the steering wheel topic... I only changed the stalk (with "mode" function) and hacked the wiring harness so that the same "mode" function on stalk can be used to control the "distance" of radar cruise. Now it works so that a short push on stalk changes the distance and a long push switches between radar/normal cruise modes. I was ready to sacrifice the "mode" functionality as I have never even used that, but there was no need for that...

BR. Sami