Disco 2 Autobox not changing up

[Green Bob]

My parents' Td5 auto Discovery isn't changing out of 1st when driven in any gear: 1, 2, 3 or D. It will just rev in 1st up to just over 3k revs then thunk up into 3rd limp home with the lights flashing. It's driveable, but it's a pain.

My dad took it to an automatic gearbox specialist and they ran it through their diagnostics which threw up a MAF fault and a speed sensor fault. I couldn't imagine the MAF fault is anything to do with it, but even so, I got him to run it with it unplugged and the gearbox was still at fault.

Now what I'm wondering is:

Is the speed sensor likely to be the culprit here? (It seems a reasonable assumption)

Where is it? (I recall seeing a photo of a step-by-step oil and filter change, which showed leads heading to what I presume was a sensor just inside the sump, is this it?)

How easy is it to pop out and replace/repair/clean?

[Ally V8]

You are right,you can forget the Maf fault,but depending on the diagnostic kit used the speed sensor fault may be a red herring too.What needs to happen is to get it on Testbook or a similar LR specific diagnostic tool where you can read the output shaft speed as live data.Even better would be to scope the sensor at the ECU plug to see wht the ECU is seeing.There are plenty of things that can go wrong that can be fixed without removing/stripping or reconning the box itself.For a start make sure the wiring loom to the box is not rubbing away at the back of the transfer box.