Abstract: A vehicle (10) is disclosed which includes a thermostat (22) in a bottom hose (24) of a radiator (16). An onboard diagnostic arrangement is provided to monitor the efficiency of the thermostat (22). Temperature sensors (S1, S2) are provided to monitor the temperature of the coolant across the radiator (16) so that a controller (40) can derive from those measurements the temperature differential across the thermostat (22). If the temperature Teng of the coolant at the thermostat inlet is below the thermostat opening temperature Topen and the differential temperature between the thermostat inlet temperature Teng and the thermostat outlet temperature Trad is below a fault threshold Dtstat, the thermostat (22) is evaluated as being stuck open or leaking, which results in a fault being recorded and a malfunction indicator lamp (MIL) being illuminated.

Abstract: A powertrain control system is disclosed in which an electronic control unit (ECU) (13) controls a power output actuator (10) to drive a fuelling element (12) of an internal combustion engine (not shown). The ECU (13) receives a signal of demanded power from an accelerator pedal demand potentiometer 915) and signal of required power output characteristic (20, 21) from a range switch (16). The ECU (13) selects the required power output characteristic (20, 21) from memory (14) and applies it to control the power output actuator (10) in relation to the pedal demand signal (25) from the demand potentiometer (15). It is thus possible to select between plural power output characteristics (20, 21) depending on vehicle use or driving conditions.