Diff lock light randomly activating

Hi all, I have been dealing with this issue on and off for the last month and it's driving me crazy.

Have had this 2013 Patrol GU (automatic) for a couple of months. First month it ran perfectly, no issues. Now it seems to randomly trigger the diff lock light at completely unpredictable times (while the diff lock switch is firmly in the 'Off' position). Doesn't matter if I've been driving for hours or just 30mins. Terrain does not matter. It's not every trip, but it is frequent enough that it's becoming a familiar pain in the ass.

The light doesn't always come on solidly straight away. Sometimes it starts with dim flickering, on and off. Sometimes it comes on then goes away for the rest of the drive. Sometimes it comes on real solid and starts beeping at me for driving above 20km/h. There is no consistency to it, and it definitely isn't activating the diff - which has been kept 'Off' since I bought the car. Usually the issue goes away once the car has been off for a few hours. But it always comes back eventually.

At one point during a 2hr drive, the beeping got to me and I unplugged the switch's wiring loom behind the face plate, but the light continued to stay on and beep! Felt like I was going crazy.

I have taken it to two mechanics now, both of which have been unable to find any cause. I asked an auto electrician about it and they'd never heard of the issue before. I was paranoid that the diff lock system was completely fucked, but apparently it is working perfectly fine when the switch is actually turned on. Oils were changed just a week ago at a preemptive service. The most recent mechanic said the best thing to do was come to the forums and see if anyone else has had any experience with this.

Please, if anyone has any knowledge on this kind of issue, I am open to any solution. I have no idea if it's an electrical issue or a mechanical issue. The mechanics seem to think wiring and parts are in perfect working order, but obviously something is wrong. Everyone who has tried to help me has been stumped.

Thank you.

Welcome to the forum. It could be an earthing issue or maybe rodents have had a bit of a chew on the wiring harness. I would suggest tracing the wiring harness and looking for chafing or shorted wires. Patrols do need good earth straps and wires to the body, engine and chassis to run properly. It would not hurt to undo each earth, clean the contact surfaces and retighten them.

I have added a wire from trailer socket earth to the chassis and the body to the chassis. Also check the connectors are all clipped in properly and there is no corrosion.

Thanks for the reply. The last mechanic that looked over it seemed to suggest that the wiring was all in good condition. I wouldn't know where to start with tracing wiring harnesses and undoing/redoing earths. Perhaps it's worth trying my luck with another auto electrician to go over all the diff lock wiring?

Download the workshop manuals available on this forum and read up how the diff lock actuates. And to get the wiring harness equipment locations