P2641: Torque Management Feedback Signal B
What to do
The engine drives normally, with more cautious gearchanges and traction control. The reasoning is at P2637.
If both an A and a B code from this group are stored, that is worth saying — two separate wires failing at once is unlikely, and something shared such as a connector or an earth point is the far more probable explanation, which is usually quicker and cheaper to find than either wire.
What this code means
A fault in the second torque feedback circuit. What the feedback is for, and why losing it makes other modules distrust a perfectly good engine, is at P2637.
Two feedback lines exist for the same two reasons two request lines do, and the reasoning is at P2548: either more than one module needs the answer and each has its own line, or one answer is carried on two conductors with a defined relationship so that no single wire fault can invent or suppress it.
On a vehicle of the second kind, a fault on B alone means the pair no longer agree, and the safe interpretation of an unverifiable torque figure is to stop relying on it — so the fallback behaviour arrives even though one of the two lines is still perfectly good.
Likely causes
Start here
- Damaged wiring harness · moderate
- Corroded or loose connector · easy
Less common
- Corroded earth connection · easy
- Faulty transmission control module · specialist
Rare
- Faulty engine control module · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
Be the first to write this up
Nothing posted about this yet. Whatever you found is worth writing down — even a dead end saves someone the same afternoon.
What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
- What actually fixed it — or that nothing did, which is worth knowing too.
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