Powertrain, generic (extended)

P2638 Torque Management Feedback Signal A Range/Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2638 says the torque feedback for request A is present but its value does not fit the situation, for example an engine torque figure that drifts away from what the transmission expects during a shift. Honda documents it on its nine-speed automatic: on low-mileage 2016 Pilots the MIL lit and the gear indicator flashed because the idle learn had not been done properly before delivery, so the fix is a PCM reset with the HDS and a correct idle relearn. Service bulletins 16-008 (Pilot) and 16-012 (Acura TLX V6) later improved the torque accuracy monitoring behind P2638 by TCM software, again followed by an idle learn. Unlike P2637, where the engine ignores the request, here the reported torque is implausible. Drivers notice rough or delayed shifts.

Likely causes

Idle learn not completed after PCM reset or delivery
Outdated transmission software with oversensitive torque monitoring
Engine torque estimate skewed by air leaks or sensor errors

Symptoms

  • MIL on and gear position indicator flashing
  • Rough or delayed gear changes

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€50–300
Time0.3–1.5 h

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

Parts involved

tcmecm

Related codes

P2637P2639P2642

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