A powertrain control system 1, for an off-road motor vehicle having an engine 5 coupled to a transmission 9 which is operable in a high range and a low range, comprises a stop/start controller 11 for issuing an engine stop request signal when one or more conditions have been met. An inhibitor 15 is provided for inhibiting operation of the stop/start controller 11 when the low range is selected in the transmission 9. An engine running signal may be issued from the stop/start controller 11 if the low range is selected when the engine 5 has been stopped by the stop/start controller 11. The stop/start controller 11 receives signals from a range detector 13 which determines that low range is selected. A terrain optimisation selector activates one of a plurality of pre-configured powertrain operating modes which includes selecting the low range. A processor monitors one or more driving characteristics and determine when the low range should be selected. Reference is also made to a method of operating the system.
