UPDATE:
I finally solved my cruise control issues! There were multiple electrical issues that I discovered after months of testing and troubleshooting. I will give a high level summary of what I had to do.
I first identified that the system would not work noting there were no self-diagnostic blink codes, which ruled out an ECU fault path.
Next using the diagnostic guide in the manual verified all the inputs (main switch, brake, neutral, parking brake, and speed sensor power/ground) were in spec.
That's when I found no usable signal reaching the cruiser control ECU, explaining the lack of engagement and error codes. I followed the instructions on this post to rebuild the speed sensor.
cruise control trouble - https://forum.ih8mud.com/threads/cruise-control-trouble.586112/post-14047856 Post #45.
I ordered a few hall effect switches from Digikey:
MAGNETIC SWITCH LATCH TO92-3 DigiKey part number: 296-DRV5013AGQLPG-ND.
Then I modeled and 3d printed a new assembly out of PETG for the switch soldered it and potted it with UV resin. If anyone wants this file please reach out.
After I installed the new sensor I tested the ECU and confirmed it was receiving a signal on Pin 20 when the shaft was spun by hand.
Then I went for a test drive and finally received an error code pointing to the Cruise control motor actuator assembly. I pulled the assembly and bench tested it using the instructions found in the manual. The signal from the internal potentiometer was erratic and out of spec when measured through its sweep. Resistance did not change smoothly or within the FSM’s expected range, indicating a worn or damaged potentiometer track.
I found a replacement potentiometer on
ebay and soldered it in place. RV16YN15S B202-Cosmos. The assembly of the unit was a tricky getting it all lined up correctly.
After it was re-assembled I bench tested it with 12 volts and walked through the procedure in the FSM. It passed all tests.
Then I installed it in the truck and went for a test drive following the cruise control test steps, that I had do so many times before. I received the same error indicating no signal from the actuator. I threw up my hands and started searching for a new actuator. Since it is RHD finding a new one was prohibitively expensive and very hard to find. I gave up and moved onto other projects. I replaced the drivers side inner fender, installed a new turbo, PDI intercooler kit, custom air box and while I had it apart I cleaned all the wiring in this area. I removed all the factory harness tape and split tubing. Inspected all the wires, cleaned all the connectors thoroughly then re-taped and sealed the looms. Once the Landcruiser was driving again I tried the cruise control and it worked! Imagine how happy I was. I believe cleaning the round plug connector to the actuator fixed the issue. Now I have working cruise control and I use it every chance I get, it works flawlessly.
