Forum:
I thought I posted on here a few months about about the flashing D?
Anyway here is the lowdown:
The flashing D is caused by the pressure sensor on the gearbox, If there is not sufficient oil pressure in the auto gearbox, the light is triggered. Or of course the sensor could be duff.
So the reasons for the flashing D are.
Poor quality old oil, or oil is too thick and not flowing fast enough when cold. (30 secs idle when cold before engaging D is advised)
Oil too low.
Or a dicky sensor, (most likely damaged from dirty oil)
Well at least we know what it
Well at least we know what it is now
Took 4 years for the answer. Thanks Nathan 
Another sensor to add to the shopping list
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'12' Plate Mazda MX-5 2.0 litre NC 3.5 Venture Roadster 160BHP
'15' Plate SEAT LEON 184 FR TDI. 240BHP/500nm Torque.
Past: '53' Plate Yellow YRV Turbo Approx. 150BHP
Im not sure if it is screwed
I'm not sure if it is screwed into the gearbox casing, or integral inside the box. Not looked.
There could be a easy fix if the sensor is playing up and if too expensive to replace it. I guess it works like a oil pressure switch..2 wires from it.
If we know which wires in the gearbox loom then you could join them together. As far as the gearbox computer/ecu would know, the sensor is then working.
There is also a gearbox oil
There is also a gearbox oil temp sensor. When the oil is not up to temperature (hence not flowing fast enough) in Steer-Shift mode, you may have noticed that the computer won't allow certain steer shift up changes.
For example changing up into a high gear if the car speed is not high enough.
Gearbox ECU also monitors oil overheating from the temp sensor and it can deactivate Steer Shift if the oil temp gets too high.
It talks about this feature in the owners handbook.
We are learning things new
We are learning things new every day
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'12' Plate Mazda MX-5 2.0 litre NC 3.5 Venture Roadster 160BHP
'15' Plate SEAT LEON 184 FR TDI. 240BHP/500nm Torque.
Past: '53' Plate Yellow YRV Turbo Approx. 150BHP