Method for Detecting a Nonoperational Shift Element in an Automatic Transmission

A method for detecting a malfunctioning shift element in an automatic transmission, comprising:

• operating the automatic transmission in an initial gear, a selected shift element of the automatic transmission being in an engaged configuration when the automatic transmission is in the initial gear;
• terminating a power flow from the automatic transmission after said step of operating the automatic transmission in the initial gear;
• shifting the automatic transmission to an intermediate gear after said step of terminating, the selected shift element of the automatic transmission being commanded to a disengaged configuration when the automatic transmission is in the intermediate gear;
• measuring a gear ratio of the automatic transmission while the automatic transmission is operating in the intermediate gear;
• determining whether the selected shift element of the automatic transmission is malfunctioning based at least in part on a difference between the gear ratio of the automatic transmission in the intermediate gear from said step of measuring and a predetermined gear ratio;
• and
• shifting the automatic transmission to a subsequent gear if the selected shift element of the automatic transmission is not malfunctioning at said step of determining or continuing to operate the automatic transmission in the intermediate gear if the selected shift element of the automatic transmission is malfunctioning at said step of determining.

A method for detecting a malfunctioning shift element in an automatic transmission, comprising:

• terminating a power flow from the automatic transmission;
• operating the automatic transmission in an intermediate gear after said step of terminating;
• measuring a gear ratio of the automatic transmission in the intermediate gear;
• step for determining whether the selected shift element of the automatic transmission is malfunctioning;
• and
• shifting the automatic transmission to a subsequent gear if the selected shift element of the automatic transmission is not malfunctioning or continuing to operate the automatic transmission in the intermediate gear if the selected shift element of the automatic transmission is malfunctioning.