Do you have an OBD scanner that can read live data? I'll bet you aren't getting some sort of signal. TPS or road speed would be my guess. I had an issue with a 1999 D2 that couldn't get a good road speed signal from the SLABS.... it always thought it was moving down the road at 88mph. I cleaned some corrosion inside the ECM and it was ok after that.
A land rover specific computer would be able to tell you exactly which P1884 code it is, as there are 9 codes that all pop up in generic OBD2 as P1884.
P1884 (11) * CAN message:Engine friction invalid No apparent effect. On Off
P1884 (18)* CAN message: Throttle position invalid Substitute throttle angle of 50% adopted. No kickdown. Operates in economy modes only. On On
P1884 (19) CAN message: Engine temperature invalid Substitute engine temperature derived from other inputs. No apparent effect. On Off
P1884 (20) CAN message: Road speed invalid No apparent effect On Off
P1884 (33, 34) * CAN message: Engine torque invalid Substitute engine torque of derived from other inputs. May affect shift quality. On Off
P1884 (35) * CAN message: Engine speed invalid Maintains current gear in low range, limp home mode in high range. Shift pressure to maximum, harsh gear shifts/engagement. On On
P1884 (37) CAN message: Engine air intake temperature invalid No apparent effect. On Off
P1844 (38) Altitude shift control invalid No reduced torque compensation, possible reduction in performance/ driveability at
altitude or high ambient temperatures. On Off