Alright - so I own an interesting Defender 90 - it's part Defender and part Discovery 1.
Pics below.
It's mildly famous because it was the actual Defender in the iPhone 12 commercial - some pics below - and video
It's a RHD 1984 Defender body and Defender Axles, Gas tank, but the Engine is 1996 Disco 1 (as is the Evap system, Electrical, Dash, Transmission and pretty much all innards - up to and including the 10AS and the GEMS)

The other day it randomly just stopped starting.
It would crank but not start.

Had spark, Fuel Pump was fine, had gas, Crankshaft speed sensor fine - checked it on the scope everything looked good.
Checked all the wires that I could (once my friend and experienced mechanic got me a wiring diagram).

Then realised that the GEMS wouldn't go into Security Learn mode.

There's no spider on a 1996 Disco 1 - so no spider bypass.
So what was left?

My option were

1. New ECU
2. New 10AS

But I had no obvious way of diagnoising whether either of those were at fault. And then...I found Lee Bourgeois at LabTronx

OMG he makes a thing called the Mobi4 (at the above link) and it basically mimics the 10AS correctly.
As in - you swap out three wires (Power, Ground and Signal) and you don't need the 10AS for Security Learn anymore.

(btw I tried to a new ECU - didn't make a difference - and I actually also tried another 10AS which didn't work. Lee told me that 10AS frequently mess themselves up, ECU's rarely so)

Anyway - hopefully this will save people time and money.

Nick


Early morning wake-up - El Mirage