P2640Torque Management Feedback Signal A High
- Generic OBD-II code · Powertrain
- Can trigger limp mode
- How the car detects it
- P2640 is the high-range fault of torque management feedback signal A: the confirmation that the transmission controller receives after asking the engine for a torque change carries a value above the plausible upper limit. On Allison-equipped trucks this feedback is not a separate wire but part of the engine data broadcast on the J1939 link, so a high reading usually means the engine claims more torque than is physically possible or than was requested. No manufacturer documents P2640 publicly. For the related P2637 Cummins cured the fault with new ECM calibrations, a hint that software mismatches are a frequent root. P2637, P2638 and P2639 cover the general, plausibility and low faults of signal A. Expect harsher shifts and torque reductions that no longer work.
- What you may notice
- Check transmission lamp or MIL on, depending on calibration
- Firm or abrupt upshifts
- Torque reduction during shifts no longer active
- Likely causes
- LikelyEngine ECM software reports torque values the transmission calibration does not accept
- PossibleOutdated or wrong transmission controller calibration
- RareHard-wired feedback line shorted to voltage (where used)
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €80 – €600
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.