Brake-switch failure diagnosis method and brake-switch failure diagnosis system

A brake-switch failure diagnosis program, executed in a brake-switch failure diagnosis system configured to be inputted with output signals from two brake switches for detecting an operation condition of a brake pedal so that failure diagnosis of the brake switches is performed, characterized by having:

• a first step that whether the output signals from the two brake switches are in an ON-state together is determined,
• a second step that when the output signals from the two brake switches are determined to be in the ON-state together in the first step, a first determination counter is cleared,
• a third step that when the output signals from the two brake switches are determined to be not in the ON-state together in the first step, whether the output signals from the two brake switches are in an OFF-state together is determined,
• a fourth step that when the output signals from the two brake switches are determined to be in the OFF-state together in the third step, a second determination counter is cleared,
• a fifth step that when the output signals from the two brake switches are determined to be not in the OFF-state together in the third step, a determination delay timer performs timing of a certain time,
• a sixth step that when the determination delay timer completes the timing of the certain time in the fifth step, whether the output signals from the two brake switches are in the ON-state together is determined,
• a seventh step that when the output signals from the two brake switches are determined to be in the ON-state together in the sixth step, the first determination counter is cleared,
• an eighth step that when the output signals from the two brake switches are determined to be not in the ON-state together in the sixth step, whether the output signals from the two brake switches are in the OFF-state together is determined,
• a ninth step that when the output signals from the two brake switches are determined to be in the OFF-state together in the eighth step, the second determination counter is cleared,
• a tenth step that when the output signals from the two brake switches are determined to be not in the OFF-state together in the eighth step, the first and second determination counters perform count of predetermined incremental values being determined respectively,
• an eleventh step that after the first and second determination counters perform the count respectively in the tenth step, whether count values of the counters are equal to or larger than predetermined values being set respectively is determined, and
• a twelfth step that when one of the count values is determined to be equal to or larger than the predetermined value in the eleventh step, one of the two brake switches is regarded to be failed,
• wherein the program is configured such that these steps are periodically repeated.

A brake-switch failure diagnosis system for detecting an operation condition of a brake pedal, characterized by having:

• two brake switches, each outputting a predetermined signal depending on an operation condition of a brake pedal, and
• an electronic control unit that is inputted with respective output signals from the two brake switches to determine presence of failure of each brake switch,
• wherein the electronic control unit is configured to operate so that
• detection is made on a situation that the two brake switches are not ON together and not OFF together, and when such a situation is detected, first and second determination counters perform count of respective predetermined incremental values, and on the other hand, when the two brake switches are detected to be ON together, a count value of the first determination counter is set to zero, and when the two brake switches are detected to be OFF together, a count value of the second determination counter is set to zero, those operation being periodically repeated, and
• when the count value of the first determination counter or the count value of the second determination counter is equal to or larger than each predetermined value being beforehand determined, a brake switch is determined to be failed.