What it means
The third intermediate shaft speed sensor returns no usable signal. Used on transmissions with multiple intermediate planetary stages.
At a glance
- Usually lights the check-engine light
How it works
Intermediate shaft speed sensor C measures the rotation of a third intermediate shaft and reports it to the transmission control module. P2749 indicates that the module cannot obtain a usable signal from sensor C, which may result from an open sensor element, broken signal wire, or corroded connector.
Common causes
Most likely first.
- Open sensor element or broken signal wire
- Corroded sensor connector
Symptoms
- Check-engine or transmission warning light on
- Harsh or delayed shifts
- Speedometer or gear indication may behave erratically
- Transmission may enter limp mode
How to diagnose it
- Save freeze-frame data and check live sensor C speed against input and other shaft speeds while the transmission is operating.
- Inspect sensor C's connector and nearby wiring for corrosion, loose terminals, or a broken wire.
- Check whether sensor C reports no usable speed while the other shaft readings change.
- Test sensor C's signal circuit and electrical connections using the wiring diagram and manufacturer's specifications.
- If the electrical tests pass, inspect the sensor's target and mounting for damage or an installation issue.
Common fixes
- Reconnect sensor C and repair corroded connector terminals.
- Repair an open or damaged sensor C signal wire.
- Replace the failed intermediate shaft speed sensor C.
- Repair a damaged sensor target or correct the sensor mounting if inspection identifies a fault.
Can I keep driving?
Drive gently only as needed to reach a safe location; missing sensor C data can lead to harsh shifts or limp mode. Avoid towing and stop if the transmission slips or shifts unpredictably.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.