referring to the drawings , wherein like reference numerals are used to identify like or identical components in the various views , fig1 schematically illustrates a hybrid powertrain 10 for a hybrid diesel - electric vehicle . the hybrid powertrain 10 may include an internal combustion engine 12 in mechanical communication with an electric traction motor 14 ( electric motor 14 ). the internal combustion engine 12 may generally be controlled by an engine control module 16 ( ecm 16 ), while the electric motor 14 may generally be controlled by a hybrid control module 18 ( hcm 18 ). the ecm 16 and hcm 18 may be embodied as one or multiple digital computers or data processing devices , having one or more microcontrollers or central processing units ( cpu ), read only memory ( rom ), random access memory ( ram ), electrically - erasable programmable read only memory ( eeprom ), a high - speed clock , analog - to - digital ( a / d ) circuitry , digital - to - analog ( d / a ) circuitry , input / output ( i / o ) circuitry , and / or signal conditioning and buffering electronics . each module 16 , 18 may be configured to automatically perform one or more control / processing routines that may be embodied as software or firmware associated with the module 16 , 18 . while fig1 generally illustrates one particular configuration of a hybrid diesel - electric vehicle , other arrangements may be similarly applicable to the presently described technology . likewise , additional electric motors may be included in various arrangements within the powertrain 10 to serve as the primary movers for the hybrid vehicle . as such , the engine 12 and electric motor ( s ) 14 may be in power - flow communication with each other and with a transmission 20 to ultimately power a drive shaft 22 and one or more drive wheels 24 . the electric motor 14 may provide one source of torque via a motor output shaft 26 . similarly , the engine 12 may generate torque via a crankshaft 28 , which may be selectively coupled with the motor output shaft 26 through a clutch 30 and / or one or more planetary gear sets ( not shown ). torque from the crankshaft 28 can be used to directly propel the vehicle 10 , and / or to drive the electric motor 14 as a generator to recharge a traction battery 32 . the electric motor 14 may be embodied as a multi - phase permanent magnet / ac induction machine rated for approximately 60 volts to approximately 300 volts or more depending on the vehicle design . the electric motor 14 may be electrically connected to the traction battery 32 via a power inverter module ( pim ) 34 and a high - voltage bus bar 36 . the pim 34 may generally be configured for converting dc power to ac power and vice versa as needed . the battery 32 may be selectively recharged from torque applied to the electric motor 14 when that motor 14 is actively operating as a generator , e . g ., by capturing energy during a regenerative braking event or when being driven by the engine 12 . as may be appreciated , the electric motor 14 may be an electric motor , an electric generator , a motor / generator , or any combination thereof . in some embodiments , such as plug - in hev ( phev ), the battery 32 may also be recharged via an off - board power supply ( not shown ) when the vehicle 10 is idle . the engine 12 may be in fluid communication with an air intake 40 and one or more fuel injectors 42 . the air intake 40 may be configured to provide a supply of fresh air to the engine , where the air may mix with the fuel from the fuel injector 42 . a variable throttle 44 may controllably modulate the flow of air from the intake 40 to the engine 12 , under the direction of the ecm 16 . likewise , the ecm 16 may control the flow of fuel into the engine 12 via the one or more fuel injectors 42 . in one configuration , an intake manifold 46 may be disposed between the throttle 44 and the engine 12 to allow the intake are to evenly flow into the engine 12 . in addition to the ecm 16 and hcm 18 , the powertrain 10 may further include a transmission control module 48 ( tcm 48 ) that may supervise the operation of the transmission 20 . the tcm 48 may be in communication with each of the ecm 16 and hcm 18 , and , in an automatic transmission configuration , may aid in coordinating gear changes within the transmission 20 . for example , during a gear change , the net torque transmitted through the transmission 20 may desirably be at some predetermined value that is lower than the driver - requested torque . in this manner , the ecm 16 and / or hcm 18 may momentarily override any driver - requested torque commands to facilitate the gear - change in cooperation with the tcm 48 . during operation , the electronics within the ecm 16 , hcm 18 , tcm 48 , pim 34 , and / or electric motor 14 may generate thermal energy ( heat ) as a product of internal electrical resistances and / or transistor switching . due to the packaging requirements within the vehicle 10 , each component may require various amounts of active cooling to remove the generated thermal energy before it accumulates to a point where electrical circuits begin to degrade . such active cooling may be provided through a liquid coolant ( not shown ) that may be selectively pumped through each component to transport the thermal energy to a radiator or other thermal extraction device . to properly determine the amount of active cooling required ( e . g . fluid flow rate ), a thermal control module 50 may monitor one or more temperature sensors 52 associated with each respective electrical component ( i . e ., the ecm 16 , hcm 18 , tcm 48 , pim 34 , and / or electric motor 14 ). the thermal control module 50 may be embodied in software or firmware associated with the ecm 16 , the hcm 18 , and / or another such controller . throughout the life of the vehicle 10 , it may be necessary to perform routine diagnostics on the various temperature sensors 52 to ensure that they are properly functioning and reporting accurate temperatures . such sensor diagnostics may be embodied as algorithms within the thermal control module 50 , and may be configured to dynamically offset sensors that have begun to drift , and / or may provide an indication to disregard readings from inoperable sensors . fig2 illustrates a diagnostic method 100 that may be used to evaluate the operation of a temperature sensor 52 associated with an electrical component of the vehicle 10 . as will be described in greater detail below , the method 100 generally involves using average temperature readings to infer an operational status . when using such a diagnostic strategy , it is important that the systems under measurement ( i . e ., the ecm 16 , hcm 18 , tcm 48 , pim 34 , and / or electric motor 14 ) are all approaching a common temperature so that their respective readings may be reconciled against each other . therefore , in step 102 , the method 100 may begin when the thermal control module 50 identifies a power - down event where the vehicle is placed into “ park ” and / or a “ key - off ” event occurs ( i . e ., an operator key is transitioned to an “ off ” state ). once the various systems / control modules are de - energized and / or placed into a reduced state of operation ( i . e ., a non - operational state ), the thermal control module 50 may initiate a running timer at step 104 . the running timer may be used to track the total amount of time that the vehicle is in the “ off ” state . at step 106 , the ecm 16 may detect a key - on event , at which time the various vehicle systems may be energized and brought back up to an operational state . immediately following the key - on event , at step 108 , the thermal control module 50 may compare the count from the running timer to a threshold . if the count is below the threshold the method may restart . conversely , if the count is above the threshold ( i . e ., the vehicle has been in a power - off state for longer than a predetermined amount of time ), the thermal control module 50 may initiate a temperature sensor diagnostic routine 110 . the predetermined threshold used in step 108 may be selected according to the thermal dynamics of the various vehicle systems such that after the prescribed amount of time , the temperature of all systems under measurement may all trend to a common temperature . in most circumstances , this common temperature may approximate the ambient air temperature external to the vehicle . for example , in one configuration , the predetermined threshold used in step 108 may be approximately 8 hours . depending on the vehicle configuration , this may be the minimum amount of time required for the various internal components to all cool from an operating temperature to approximately an ambient temperature . it should be noted that while some smaller components may cool more rapidly , others , such as a motor housing , an engine block , various heat sinks , a cooling fluid , etc . may retain more heat for a longer period of time . once the temperature sensor diagnostic routine 110 is initiated at step 108 ( i . e ., each of the respective electrical systems have been maintained in a non - operational state for the predetermined period of time ), the thermal control module 50 may initially perform an electrical integrity check on each of the various temperature sensors 52 within the vehicle 10 ( step 112 ). the electrical integrity check may ensure that each temperature sensor is powered on , is neither shorted nor open , and is reporting some temperature reading . if all sensors are electrically active , the thermal control module 50 may then poll each respective sensor to receive a preliminary temperature reading at step 114 . after sitting in an “ off ” state for a predetermined amount of time , each respective temperature sensor 52 should return a temperature value that is approximately equal to the ambient air temperature . in step 116 , the thermal control module 50 may then determine the median of the plurality of temperature sensor readings , which may then serve as a single , master - reference temperature value . as will be described below , the master - reference temperature value may be used to reconcile the readings of each respective temperature sensor , despite those sensors not being necessarily in close physical proximity to each other nor necessarily monitoring the same systems . each of the various temperature readings may then be compared to the master - reference temperature value determined in step 116 . for example , in step 118 , the difference between each respective temperature reading and the master - reference temperature value may be compared to a first threshold . if the respective difference is above the first threshold , but below a second , greater threshold ( compared at step 120 ), an offset may be applied to the temperature sensor that is equal to the difference between the temperature reading and the master - reference temperature value ( at step 122 ). if , however , the difference exceeds the second threshold , that sensor reading may be disregarded , and the sensed system or cooling provided to that system may be operated in a conservative manner to avoid unintentionally overheating the system ( at step 124 ). if the temperature difference between each respective temperature reading and the master - reference temperature value then the reading may be regarded as operational and accurate . if the difference between the temperature reading of a particular sensor and the master - reference temperature value exceeds the first and / or second thresholds , the thermal control module 50 may provide a warning indicator to the driver of the vehicle ( e . g ., via a light on an instrument panel ), or note the deviation in an on - board diagnostic ( obd ) log ( at step 126 ). such an indication may provide notice to a driver that the vehicle requires service , and / or may alert a trained service technician that a sensor may require further evaluation . fig3 illustrates a second diagnostic method 200 that may be used to evaluate the operation of a temperature sensor 52 associated with an electrical component of the vehicle 10 . similar to the method 100 illustrated in fig2 , the method 200 of fig3 begins at step 102 when the thermal control module 50 identifies a power - down event where the vehicle is placed into “ park ” and / or a “ key - off ” event occurs ( as such , all electrical systems may be brought to the non - operational state ). the thermal control module 50 may then initiate a running timer at step 104 , and eventually detect a key - on event at step 106 . immediately following the key - on event , the thermal control module 50 may compare the count from the running timer to a threshold ( step 108 ). if the count is above the threshold ( i . e ., the vehicle has been maintained in the non - operational / power - off state for longer than a predetermined amount of time ), the thermal control module 50 may initiate a temperature sensor diagnostic routine 210 . once the temperature sensor diagnostic routine 210 is initiated at step 108 , the thermal control module 50 may perform an electrical integrity check on each of the various temperature sensors 52 within the vehicle 10 ( step 212 ). the electrical integrity check may ensure that each temperature sensor is powered on , is neither shorted nor open , and is reporting some temperature reading . if all sensors are electrically active , the thermal control module 50 may then poll each respective sensor to obtain a preliminary temperature reading at step 214 . as described above , after sitting in an “ off ” state for a predetermined amount of time , each respective temperature sensor 52 should return a temperature value that is approximately equal to the ambient air temperature . in step 216 , the thermal control module 50 may then determine the median of the plurality of temperature sensor readings . using the median temperature , the thermal control module 50 may then perform a separation check ( step 218 ), whereby each temperature sensor reading is compared to the median temperature . if the difference between a temperature sensor reading and the median temperature exceeds a threshold difference , then that particular sensor may be excluded from the collection of sensor readings for subsequent computations . conversely , if the difference between a temperature sensor reading and the median temperature is less than a threshold difference , that particular sensor may be included in subsequent computations . in one configuration , the temperature threshold used for the separation check may be approximately +/− 5 degrees celsius all sensors that pass the separation check ( i . e ., are within a predetermined range of the overall median temperature reading ) may then be averaged in step 220 to form a master - reference temperature value . said another way , the master - reference temperature value may be the mean temperature of the subset of temperatures that are within a predefined temperature range of a median temperature of all of the temperature sensors . such a calculation may be performed after a suitable cold - soak , whereby the temperature of all vehicle systems and temperature sensors are expected to approach a common ambient temperature . the separation check is used to eliminate any sensors from consideration that are not close enough to the presumed ambient temperature to be within normal variance ( i . e ., some sensor abnormality would then be presumed to cause the abnormal variance ). following the separation check , the averaging of all remaining sensors may generate a statistical average that accounts for the normal variability between the functioning sensors . once the master - reference temperature value is determined , each respective temperature sensor readings may be compared to the master - reference temperature value as generally described in fig2 . for example , in step 222 , the difference between each respective temperature reading and the master - reference temperature value may be compared to a first threshold . if the respective difference is above the first threshold , but below a second , greater threshold ( compared at step 224 ), an offset may be applied to the temperature sensor that is equal to the difference between the temperature reading and the master - reference temperature value ( at step 226 ). if , however , the difference exceeds the second threshold , that sensor reading may be disregarded , and the sensed system or cooling provided to that system may be operated in a conservative manner to avoid unintentionally overheating the system ( at step 228 ). if the temperature difference between each respective temperature reading and the master - reference temperature value then the reading may be regarded as operational and accurate . if the difference between the temperature reading of a particular sensor and the master - reference temperature value exceeds the first and / or second thresholds , the thermal control module 50 may provide a warning indicator to the driver of the vehicle ( e . g ., such as by illuminating a light on an instrument panel ), or may note the deviation in an on - board diagnostic ( obd ) log ( at step 230 ). such an indication may provide notice to a driver that the vehicle requires service , and / or may alert a trained service technician that a sensor may require further evaluation . while the best modes for carrying out the invention have been described in detail , those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims . it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not as limiting .