The 14CUX is prone to producing erroneous error flags. I have modified the code to enable the MIL light, and wired in a MIL light, to my +8, and it comes on randomly with no actual error code being stored. My understanding is that the function (MIL light) was disabled in the 14CUX used in the Discovery, probably because of the tendency to set the MIL light flag for no good reason. I often found that when the MIL light comes on, it clears with ignition off and back on again. Whereas a hard error stays, and has to be cleared with a reader, or the red key.
The neutral error is code 69 and basically prevents the vehicle from starting unless the gearbox is in neutral (or park ?). The signal comes in on pin 34 of the ECU (possibly an orange/black wire). I would expect that the signal wire would be grounded when in neutral, maybe via a resistor. Probably inhibits the fueling when not in neutral.
The Discovery wiring diagram shows an orange/black wire connection from pin 34 to a resistor that goes to ground in the case of a manual transmission (so always in neutral).
As you had a spark, and the initial running of the fuel pump, maybe the problem was that the injectors were not enabled, either due to this neutral switch issue, or the absence of the signal from the coil to the ECU, which comes via a black, rectangular, resistor that is in the wiring loom very close to the coil, you may actually find two resistors.
Probably a good idea to check the resistors near to the coil (you may find them wrapped in tape) and make sure the connections are good, and check grounding points from the loom to the body.
I had read somewhere that Mark Adams had disabled some of the unused diagnostics, don't know if he will have disabled this 'neutral' check, I will see if I can find the reference
