Technical Description of OBD-II Trouble Code
The Circuit Range/Performance of Intermediate Shaft Speed Sensor A
What does that signify?
This is a generic diagnostic trouble code (DTC) that typically applies to OBD-II vehicles with automatic transmissions. This may include vehicles from Mazda, Toyota, Chrysler, Ford, VW, Dodge, Jeep, Mercedes, Lexus, Chevrolet, etc.
Although it is a generic code, the exact repair steps may vary depending on the year, make, model, and powertrain configuration of the vehicle.
The intermediate shaft, also known as the layshaft, helps distribute rotational force from the input drive to the output shaft inside the transmission. The speed of the intermediate shaft depends on the gear you are in. In a manual transmission, the gear selector determines this, so there is no need to monitor the speed of the intermediate shaft.
However, in an automatic transmission, the gear you are in is determined by the TCM (Transmission Control Module) using multiple sensor inputs. One of these sensors is the Intermediate shaft speed sensor. The TCM requires this specific input to determine and adjust hydraulic pressures, shift points, and patterns. Experience in diagnosing other types of speed sensors (e.g., VSS (Vehicle speed sensor), ESS (Engine Speed Sensor), etc.) will be helpful here as most speed sensors have a similar design.
The ECM (Engine Control Module) in conjunction with the TCM (Transmission Control Module) may activate the P0792 code and associated codes (P0791, P0793, P0794) when they detect a fault within the intermediate shaft speed sensor or its circuits. Sometimes, when the sensor fails, the TCM uses other speed sensors within the transmission to determine a “backup” hydraulic pressure in order to keep the automatic transmission functional, but this may vary significantly between manufacturers.
The code P0792 Intermediate Shaft Speed Sensor A Circuit Range/Performance is set by the ECM (engine control module) and/or the TCM (transmission control module) when they detect an out of range condition within the A speed sensor or its circuit. Refer to a vehicle-specific repair manual to determine which part of the circuit corresponds to the “A” designation for your particular application.
NOTE: If multiple warning lights are illuminated (e.g., Traction control, ABS, VSC, etc.), record any active codes in other systems.
Photo of a transmission speed sensor:
What is the severity of this DTC?
I would classify this fault as moderately severe. As mentioned earlier, your automatic transmission may still be functioning properly. However, it could also indicate one or more larger and more pressing issues. It is best to diagnose any transmission issue as soon as possible.
What are some of the symptoms of the code?
Symptoms of a P0792 trouble code may include:
What are some of the common causes of the code?
Causes for this P0792 engine code may include:
What are some P0792 troubleshooting steps?
Basic Step #1
If you are researching this code, I will assume that you have already checked the transmission fluid level. If not, start with this. Make sure the fluid is clean and at the proper level. Once everything related to the fluid is in good condition, you need to locate the intermediate shaft speed sensor. Often, these sensors are mounted directly to the transmission housing.
You may even be able to access the sensor from under the hood, but this may require removing additional components such as the air cleaner and box, miscellaneous brackets, wires, etc. to gain access. Ensure that the sensor and corresponding connector are in good condition and securely connected.
TIP: If the ATF (Automatic Transmission Fluid) smells burnt, it is a sign that new fluid is needed. Consider performing a full transmission service with a new filter, gasket, and fluid.
Basic Step #2
Remove and clean an easily accessible speed sensor. This is a low-cost step, and if you find the sensor’s pickup to be excessively dirty once removed, cleaning it may resolve the issue. Use brake cleaner and a rag to ensure a clean sensor pickup. Dirt or shavings on the pickup can affect the sensor’s readings, so make sure it is clean!
NOTE: Any signs of rubbing on the pickup may indicate inadequate spacing between the reluctor ring and the pickup. Most likely, the sensor malfunctioned and is now hitting the ring. If a replacement sensor still doesn’t clear the ring, refer to the manufacturer’s procedures for adjusting the pickup/reluctor gap.
Basic Step #3
Test the sensor and its circuit. To test the sensor itself, you will need to use a multimeter and refer to the specific manufacturer’s specifications to measure different electrical values between the sensor’s pins. One useful trick is to perform these tests from the same wires but at the corresponding ECM or TCM connector pins. This will verify the integrity of the harness involved as well as the sensor.
