Patent claim: A fuel cell system comprising a fuel cell 24 generating an electric power by a fuel and an oxidant gas a reforming portion 23 generating the fuel by a source material and water a combusting portion 26 burning an anodeoff gas of the fuel cell 24 to heat the reforming portion 23 an exhaust heat recovery system 30 recovering an exhaust heat of the fuel cell system a detection sensor 24d 26b1 26b2 32b 32c 32d 41b 42c 44b 42b 41c 44c detecting a state of a physical quantity of at least one of the fuel cell 24 the reforming portion 23 the combusting portion 26 the exhaust heat recovery system 30 and a fluid flowing in and out of each of the fuel cell 24 the reforming portion 23 the combusting portion 26 and the exhaust heat recovery system 30 the fluid including the fuel the oxidant gas the source material the water and the anodeoff gas and a control device 60 controlling the fuel cell system based on an output signal from the detection sensor 24d 26b1 26b2 32b 32c 32d 41b 42c 44b 42b 41c 44c the control device 60 including a sensor malfunction determination device step 108 step 108 61 determining whether or not the output signal of the detection sensor 24d 26b1 26b2 32b 32c 32d 41b 42c 44b 42b 41c 44c is out of a first determination range for a first determination time TM1 or longer and a state error determination device steps 112 to 118 62 determining whether or not the state of the physical quantity serving as a detection target of the detection sensor 24d 26b1 26b2 32b 32c 32d 41b 42c 44b 42b 41c 44c is in an error state on a basis of whether or not the output signal of the detection sensor 24d 26b1 26b2 32b 32c 32d 41b 42c 44b 42b 41c 44c is out of a second determination range for a second determination time TM2 or longer the second determination range being narrower than the first determination range and fully included in the first determination range the second determination time TM2 being longer than the first determination time TM1 the control device 60 including a storage device step 120 65 storing a determination result from each of the sensor malfunction determination device step 706 step 108 61 and the state error determination device steps 112 to 118 62.

Related passage: Figure 2 shows a pressure sensor P2 abnormality determination routine.This determination routine is repeatedly executed at certain intervals for example of 2 milliseconds by the control device 50.When this determination routine is called up the control device 50 performs AD conversion of an analog output value from the pressure sensor P2 into digital data S11.The control device 50 then determines whether this sensor value digital value is equal to or larger than an upperlimit threshold value or smaller than a lowerlimit threshold value S12.If the sensor value is smaller than the upperlimit threshold value and equal to or larger than the lowerlimit threshold value S12 NO the pressure sensor P2 is operatingnormally and therefore the control device 50 exits this routine.If the sensor value is equal or larger than the upperlimit threshold value or smaller than the lowerlimit threshold value S12 YES there is a possibility of the occurrence of abnormality in the pressure sensor P2 due to disconnection or the like and therefore the control device 50 determines whether or not the sensor value digital value is kept equal to or larger than the upperlimit threshold value or smaller than the lowerlimit threshold value over a certain time period S13.If the sensor value is not kept in the abnormal value range over the certain time period S13 NO the sensor value in the abnormal range is considered due to a temporary detection error or the like in the pressure sensor P2 and the control device 50 determines that the pressure sensor P2 is operating normally and exits this determination routine.If the sensor value is kept in the abnormal value range over the certain time period S13 YES it can be determined that an abnormality has occurred in the pressure sensor P2 and therefore the control device 50 sets a pressure sensor abnormality flag to 1 S14 and exits this determination routine.