System and method for MHSG failure diagnosis of mild hybrid vehicle

A method for a mild hybrid starter and generator (MHSG) failure diagnosis of a mild hybrid vehicle, the method comprising:

• determining whether a catalyst activation of an exhaust gas purifier is needed after an engine start of the mild hybrid vehicle;
• determining whether to start the MHSG failure diagnosis when an MHSG is operated to assist engine torque for the catalyst activation;
• and
• determining whether there is an MHSG failure using a deviation between a required torque and an actual operating torque of the MHSG for each engine RPM.

A method for a mild hybrid starter and generator (MHSG) failure diagnosis of a mild hybrid vehicle, the method comprising:

• determining a catalyst activation of an exhaust gas purifier is needed after an engine start of the mild hybrid vehicle based on an engine RPM being equal to or higher than an idle RPM and a measured water temperature being between an upper limit and a lower limit for determining the catalyst activation;
• determining to start the MHSG failure diagnosis in response to an MHSG being operated to assist engine torque for the catalyst activation and a required torque of the MHSG for the catalyst activation being equal to or higher than a minimum torque for the MHSG failure diagnosis;
• and
• determining whether there is an MHSG failure using a deviation between the required torque and an actual operating torque of the MHSG for each engine RPM.

A system for mild hybrid starter and generator (MHSG) failure diagnosis of a mild hybrid vehicle, the system comprising:

• a data detection part configured to detect data for determining whether to activate a catalyst;
• and
• a controller configured to determine whether there is an MHSG failure using a deviation between a required torque and an actual operating torque of an MHSG for each engine RPM after determining whether catalyst activation is needed and whether to start a stage of the MHSG failure diagnosis based on the data detected by the data detection part,
• wherein, when determining whether catalyst activation is needed, the controller is configured to determine that the catalyst activation is needed based on a confirmation that an engine RPM is equal to or higher than an idle RPM upon reading a signal from a crank position sensor and based on a measured water temperature being between a predetermined upper limit and a predetermined lower limit for determining whether to activate the catalyst upon reading a signal from a water temperature sensor;
• and
• wherein the mild hybrid starter and generator (MHSG) failure diagnosis is enabled when the mild hybrid starter and generator (MHSG) operates while assisting an engine torque for catalyst heating to shorten the time for catalyst activation of an exhaust gas purifier immediately after an engine start.