Powertrain, generic (extended)

P2637 Torque Management Feedback Signal A

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modePossible

Many automatic transmissions ask the engine to cut torque briefly during an upshift and then check whether the engine actually did so. P2637 is stored by the transmission controller when that feedback for request A shows the engine did not follow. Allison names it Shift Energy Management (SEM) on its 3000/4000 series: behind Cummins L9 and X15 engines (EPA17 version) the engine failed to track the torque request closely enough, the CHECK TRANS lamp came on and Cummins fixed it with an ECM recalibration (TSB210020), with no change to Allison hardware or software. Cummins found the same on B6.7 engines in 2017 (J1939 SPN 513, FMI 7), and Navistar linked P2637 to Allison 1000/2000 calibrations causing quick, harsh upshifts. P2641 covers request B. Expect firm shifts or limited gears.

Likely causes

Engine control module calibration not following the torque reduction request
Transmission calibration not matched to the engine
J1939/CAN data link fault between engine and transmission

Symptoms

  • Check transmission lamp on
  • Harsh or too quick upshifts
  • Gear range limited

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€80–400
Time0.5–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

tcmcommunication buswiring harness

Related codes

P2638P2639P2641P0614

References: static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov, static.nhtsa.gov.