P2643 indicates the Powertrain Control Module (PCM) has detected that the torque management feedback signal B is below the expected voltage threshold. This signal communicates torque converter clutch (TCC) operation status from the transmission to the engine control system. The code is most common on Honda/Acura vehicles but may appear on other makes.
The TCC solenoid that controls torque management feedback signal B is stuck in a low-output state or internally failed.
Insufficient fluid pressure or aerated/burnt fluid prevents proper solenoid operation and signal transmission.
Damaged wiring, corroded connectors, or short-to-ground/open circuits between the TCC solenoid and PCM.
Mechanical failure inside the torque converter itself affecting the feedback signal circuit.
The dedicated transmission controller may be faulty, though this is less common than the above causes.
The engine computer itself may have failed, but this is rarely the cause and should be diagnosed only after all other possibilities are ruled out.
No. While some shops may recommend PCM replacement, it is rarely the cause of P2643. The fault is almost always in the transmission system itself (solenoid, fluid, wiring), not the engine computer.
Vehicle performance may be significantly reduced due to torque management limiting power. Avoid prolonged driving and have the issue diagnosed promptly to prevent transmission damage.
It depends. If low or contaminated fluid is the cause, a fluid service may resolve the issue. However, if a solenoid or mechanical component has failed, further repair will be needed.
Costs vary significantly by vehicle and root cause. Fluid services may cost a few hundred dollars, while TCC solenoid replacement can range from $500-$1500 depending on labor. Internal torque converter repairs are typically the most expensive.