Theory Of Operation

The purpose of the monitoring is to detect a fault in more than one of three temperature sensors. The transmission has three different temperature sensors. If any one of the three sensors fails, then the other two sensors are used as substitute with no impact on transmission control, operation or monitoring. Therefore a fault is only set on a multiple sensor failure. The three sensors consist of a discrete analog sensor outside the Transmission Control Module (TCM) which is located in the oil sump of the transmission (Oil Temperature Sensor) and two substrate (or chip) temperature sensors located in different positions on the TCM. As the TCM is embedded in the molded wiring harness lead frame, all temperatures have a strong correlation. Normally the oil temperature is used for the control of the transmission. Substrate temperatures are only used for over-temperature shutdown and rationality monitoring.