Leak and blockage diagnostic systems and methods

A diagnostic system for a vehicle, comprising:

• a first electronic circuit that generates a first difference based on a first pressure measured at a first secondary air injection (SAI) valve and a previous value of the first pressure;
• a second electronic circuit that generates a first accumulated difference based on a sum of values of the first difference generated during a predetermined period;
• a third electronic circuit that generates a first average of the values of the first difference generated during the predetermined period based on the first accumulated difference;
• a fourth electronic circuit that generates a second difference based on a second pressure measured at a second SAI valve and a previous value of the second pressure;
• a fifth electronic circuit that generates a second accumulated difference based on a sum of values of the second difference generated during the predetermined period;
• a sixth electronic circuit that generates a second average of the values of the second difference generated during the predetermined period based on the second accumulated difference;
• a seventh electronic circuit that selectively indicates that a fault is present downstream of one of the first and second SAI valves based on a difference between the first and second averages;
• and
• an eighth electronic circuit that illuminates a malfunction indicator lamp when the seventh electronic circuit indicates that the fault is present.