LR3 2008 “transmission fault”

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Hi I am driving a 2008 LR3 and all of sudden it some times shows “transmission fault” and at idle the RPM spikes slightly with a slight vibration under the seat . FYI the latest minor work done on the vehicle is changing air filter, coolant tank, break pads and ac filter change plus the major work done was the engine chain change.

Can somebody help me and suggest what could be wrong in my vehicle.

TIA
George