What does it mean?
SPECIAL NOTES: Non-professional mechanics should take that note that diagnosing code P0792 – “Intermediate Shaft Speed Sensor “A” Circuit Range/Performance” could result in the loss of some transmission fluid. This is particularly important in cases where the transmission has a “life-time” fill, since it is not easy, and sometimes impossible to refill the transmission to the correct level on a DIY basis.
Therefore, if code P0792 appears on a transmission with a “life-time” fill, the better option is to refer the vehicle to the dealer or a specialist transmission repair shop for professional diagnosis and repair. END OF SPECIAL NOTES.
OBD II fault code P0792 is a generic code that is defined as “Intermediate Shaft Speed Sensor “A” Circuit Range/Performance”, and is set when the PCM (Powertrain Control Module) or TCM (Transmission Control Module) detects an abnormal voltage in the Intermediate Shaft Speed Sensor. Note that this code only applies to applications with automatic transmissions.
As the name suggests, the intermediate shaft in an automatic transmission is located between the input drive and the final output shaft, and while its primary purpose is to transfer power from the input drive to the transmission internals, it also allows various parts of the transmission to rotate at different speeds to allow for smooth gear shifts.
To ensure smooth and efficient operation of the transmission, the PCM/TCM uses several speed sensors to continually monitor the speeds at which various transmission components rotate. Since the intermediate shaft plays a crucial role in power transmission, its rotational speed is closely monitored and compared with output data from other transmission speed sensors.
Note that since the rotational speed of the intermediate shaft is dictated by the gear the transmission is in, the PCM/TCM expects this shaft to rotate within a predefined range of speeds for each gear. Thus, should the PCM/TCM detect a signal from the intermediate shaft speed sensor that falls outside of the expected range for any reason, either the PCM or the TCM will set code P0792, and depending on the application, the control module(s) may also illuminate one or more warning lights.
However, on many applications, the PCM/TCM will also use input data from other transmission and engine speed sensors to calculate a “back-up” or “fail-safe” hydraulic pressure to keep the transmission functional, although gear selection and engine speed may be severely limited. The image below shows a typical transmission intermediate shaft speed sensor. Note that depending on the application, these sensors may have either two or three wires in their connectors.