P2751 indicates that the powertrain control module (PCM) has detected no signal from the intermediate shaft speed sensor 'C', which monitors the rotational speed of a shaft inside the automatic transmission. This sensor is critical for proper shift timing and torque converter lockup; a missing signal often triggers limp mode or harsh shifting.
The sensor itself has failed internally (open circuit, shorted, or damaged) and no longer produces a signal. This is the most common cause.
Damaged, corroded, or loose wiring between the sensor and PCM can interrupt the signal. Broken wires or poor pin contact are frequent problems.
Insufficient fluid can cause the sensor to not be fully immersed, or contaminated fluid can damage the sensor. This is less common but possible.
The sensor reads a toothed wheel inside the transmission; if the wheel is broken, missing teeth, or loose, the sensor cannot generate a proper signal.
A broken shaft, worn bearings, or other internal damage can prevent the tone wheel from rotating, resulting in no signal. This is rare but serious.
The PCM itself is very rarely the cause. Only consider this after thoroughly testing the sensor, wiring, and mechanical components. Replacing the PCM for P2751 is almost always unnecessary.
It is not recommended. The transmission will likely enter limp mode, limiting speed and gear selection, which can cause unsafe driving conditions and may lead to further transmission damage if the underlying issue is mechanical.
No. The PCM is rarely the cause of a 'no signal' code. The vast majority of cases are due to a failed sensor, wiring issues, or a damaged tone wheel. Replacing the PCM should only be considered after all other possibilities have been ruled out.
It monitors the rotational speed of the intermediate shaft (also called the input or turbine shaft) inside the automatic transmission. The PCM uses this signal to control shift timing, line pressure, and torque converter lockup.
Clearing the code may temporarily turn off the Check Engine Light, but if the underlying issue (faulty sensor, wiring, or mechanical problem) is not repaired, the code will return, often within a few drive cycles.