How Severe Is This DTC?
I would say this fault is moderately severe. As mentioned earlier, your automatic transmission may still function correctly. That said, it could also be indicative of one or more larger and more urgent issues. Diagnosing any transmission problem as soon as possible is the best strategy.
What Are Some Symptoms of the Code?
Symptoms of a P2748 trouble code may include:
- Hard shifting
- Multiple dashboard warning lights on
- Poor driving performance
- Irregular engine RPM
What Are Some Common Causes of the Code?
Causes of this P2748 engine code may include:
- Faulty or damaged intermediate shaft speed sensor
- Electrical fault in the wiring between the speed sensor and the modules used
- Internal ECM and/or TCM issue
- Other related sensors/solenoids damaged or faulty (e.g., input shaft speed sensor, output shaft sensor, shift solenoid, etc.)
- Dirty or low automatic transmission fluid (ATF)
What Are the Troubleshooting Steps for P2748?
Basic Step #1
If you’re looking up this code, I’ll assume you’ve already checked the transmission fluid level. If not, start with that. Make sure the fluid is clean and properly filled. Once the fluid is all set, you need to locate the intermediate shaft speed sensor. Often, these sensors are mounted directly on the transmission case.
You may even access the sensor under the hood, which might involve removing one or more components such as the air filter and box, various brackets, wires, etc., to reach it. Ensure the sensor and its corresponding connector are in good condition and fully connected.
TIP: Burnt-smelling ATF (automatic transmission fluid) is a sign that new fluid is needed, so don’t hesitate to perform a full transmission service with all new filters, gaskets, and fluid.
Basic Step #2
An easily accessible speed sensor should be removed and cleaned. This costs almost nothing, and if you find the sensor tip is excessively dirty once removed, you might be able to clean away your problems, literally. Use brake cleaner and a cloth to ensure a clean pickup on the sensor. Dirt and/or debris here can interfere with sensor readings, so make sure yours is clean!
NOTE: Any signs of rubbing on the sensor may indicate improper spacing between the reluctor ring and the sensor. Most likely, the sensor has malfunctioned and is now hitting the ring. If a replacement sensor still doesn’t clear the code, refer to the manufacturer’s procedures to adjust the gap between the sensor and the reluctor.
Basic Step #3
Test the sensor and its circuit. To test the sensor itself, you’ll need to use your multimeter and the manufacturer’s specific specifications to measure different electrical values between the sensor pins. A good tip is to perform these tests from the same wires but at the corresponding ECM or TCM connector pins. This will check the integrity of the involved harness as well as the sensor.