Fuel cell stack cell voltage sensor diagnostic

A method for evaluating voltage sensor output using a fuel cell stack voltage sensor diagnostic system, comprising:

• measuring an overall fuel cell stack voltage using a fuel cell stack voltage sensor;
• determining in a first level rationality test if a maximum value of the overall fuel cell stack voltage is less than a sensor limit, and if a minimum value of the overall fuel cell stack voltage is greater than the sensor limit;
• performing a second level rationality test to identify if the maximum value is greater than an average sensor signal value and if the average sensor signal value is greater than the minimum value;
• and
• conducting a third level rationality test to identify if the minimum value is less than a first predetermined threshold.

A method for evaluating voltage sensor output using a fuel cell stack voltage sensor diagnostic system, comprising:

• measuring an overall fuel cell stack voltage using a fuel cell stack voltage sensor;
• identifying a fuel cell voltage of each of a first end cell of the fuel cell stack using a first end cell voltage sensor and a second end cell of the fuel cell stack using a second end cell voltage sensor;
• determining in a first level rationality test if a maximum value of the overall fuel cell stack voltage, the fuel cell voltage of the first end cell or the fuel cell voltage of the second end cell is less than a sensor limit, and if a minimum value of the of the overall fuel cell stack voltage, the fuel cell voltage of the first end cell or the fuel cell voltage of the second end cell is greater than the sensor limit;
• performing a second level rationality test to identify if the maximum value is greater than an average sensor signal value and if the average sensor signal value is greater than the minimum value;
• conducting a third level rationality test to identify if the minimum value is less than a first predetermined threshold;
• initiating a power request to a vehicle system controller to identify if the fuel cell stack is operating in a low power mode if the minimum value is less than the first predetermined threshold;
• and
• sending a request to perform an enhanced reactant concentration test to the vehicle system controller after confirming the fuel cell stack has been operating at low power for greater than the predetermined minimum time.