P2747 indicates the Powertrain Control Module (PCM) is not receiving a signal from the transmission's intermediate shaft speed sensor B. This sensor monitors the rotational speed of the transmission's intermediate shaft, and the absence of any signal suggests an open circuit or complete sensor failure. The code is common in vehicles with automatic transmissions, particularly those from Asian manufacturers that use this sensor for shift control and speedometer input.
The sensor itself has failed electrically or mechanically, producing no output signal. This is the most common cause and typically the first component to suspect.
Damaged, corroded, or loose wiring between the sensor and PCM, including the connector pins, can create an open circuit preventing signal transmission.
The tone ring (also called a chopper or reluctor) mounted on the intermediate shaft may have missing, bent, or damaged teeth, preventing proper sensor triggering.
The sensor may be improperly installed, at incorrect air gap, or the mounting bolt may be loose, causing no signal or intermittent signal.
In some sensor designs, low fluid level or severely contaminated fluid can affect sensor operation or cause electrical issues.
The PCM itself may have failed, failing to recognize the sensor signal. This is the least likely cause and should only be considered after all other possibilities are verified.
They are related but may be different sensors depending on transmission design. Some transmissions have multiple speed sensors monitoring different shafts (input, output, intermediate), and P2747 specifically refers to sensor B on the intermediate shaft.
It is not recommended to drive long distances with this code present. The transmission will likely enter limp mode to protect itself, resulting in severely limited performance and potential drivability issues. Have it diagnosed promptly.
PCM failure is rarely the cause of P2747. The overwhelming majority of cases are resolved by repairing wiring, replacing the speed sensor, or fixing the tone ring. A competent diagnosis should rule out all sensor and circuit issues before concluding the PCM is at fault.
It often does, since sensor failure is the most common cause. However, proper diagnosis is essential to ensure the sensor was actually the problem and not a symptom of underlying wiring issues or a damaged tone ring, which would cause the new sensor to fail as well.