What it means
The control module monitors torque management feedback signal B and sets this code when the reported value falls below its expected range.
At a glance
- Usually lights the check-engine light
How it works
The powertrain control module monitors torque management feedback signal B as a message received over the vehicle network. P2643 is set when that reported value is below the expected range, including when the source module sends an invalid low value or the bus signal is stuck low.
Common causes
Most likely first.
- Source module sends invalid low value
- Signal stuck low on the bus
Symptoms
- Reduced engine power or torque
- Hesitation or sluggish acceleration
How to diagnose it
- Record freeze-frame data and check whether low torque feedback coincided with hesitation or reduced power.
- Read live data for signal B and compare it with the source module's status and related torque values.
- Scan other modules for faults that identify an invalid low report or network communication problem.
- Inspect CAN connectors and wiring for shorts, damaged insulation, corrosion, or poor grounds that could hold the message at a low value.
- Test network communication and the source module's reported value using the manufacturer's diagnostic procedure.
Common fixes
- Repair corroded or loose network connectors and grounds.
- Repair a shorted or damaged CAN wire causing the signal to remain low.
- Correct a source module fault that is generating an invalid low value.
- Replace or reprogram the source module if its output remains low after network wiring checks.
Can I keep driving?
Use caution if torque is reduced or acceleration hesitates, especially when joining fast traffic. Avoid strenuous driving and stop if the vehicle cannot maintain a safe speed.
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.