Powertrain, generic (extended)

P2D57 Generator B Control Circuit Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2D57 belongs to a second alternator, called generator B, as fitted to some heavy trucks; GM, for instance, offered a secondary generator (option KHB) on 2019 Silverado medium-duty trucks with the 6.6 L diesel. The code concerns the control channel of that machine: the engine computer's command and the regulator's response do not fit together, or the signal leaves its plausible band. No manufacturer documents P2D57 publicly. Infineon's LIN regulator chip TLE8881-3 shows what such a regulator reports: an electrical error flag for a field terminal shorted to ground or battery, an open field winding or excessive battery voltage, debounced over 250 or 1,000 ms; if communication stops, it falls back to a default set point. Generator A uses P065B. The charge lamp may light.

Likely causes

Damaged control line (LIN or command wire) or corroded connector
Faulty voltage regulator of the second alternator
Replacement alternator with an incompatible regulator

Symptoms

  • Charge warning lamp or message
  • Second alternator charges at a fixed default voltage or not at all

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€50–700
Time0.5–2.5 h

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

Parts involved

generator bvoltage regulatorwiring harnessecm

Related codes

P2D58P2D59P065BP2CC1P0620

References: infineon.com, static.nhtsa.gov.