Powertrain, generic (extended)

P2788 Auto Shift Manual Adaptive Learning at Limit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleRequired
Limp modePossible

P2788 is the system-level code for an automated manual gearbox whose learned correction values have reached the end of their allowed range. Such units learn the clutch bite point, engagement speed and the end stops of the shift and select movements so that gear changes stay smooth as parts wear; when a value would have to move beyond its limit, the controller can no longer compensate and stores this code. No manufacturer documents P2788 publicly; it falls under the comprehensive component rules of CARB 13 CCR 1968.2. Allison's bulletins on the related P2789 show the usual route: check whether engine torque data are plausible and whether newer software exists before replacing parts. Also check clutch wear, actuator travel and whether a relearn was skipped after repair. P2789 and P278F are the clutch-specific versions.

Likely causes

Worn clutch moving the bite point beyond the learnable range
Basic setting or relearn skipped after clutch, actuator or module work
Worn or sticking shift and clutch actuators changing their travel
Outdated software or implausible engine torque signal

Symptoms

  • Jerky take-off and harsh or slow shifts
  • Transmission warning lamp
  • Clutch slip or engine flare during shifts

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,800
Time0.5–6 h

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

Parts involved

tcmclutch

Related codes

P2789P278FP0919

References: law.cornell.edu, en.wikipedia.org, static.nhtsa.gov.