Powertrain, generic (extended)

P28D4 Clutch B Motor Phase U-V-W Circuit/Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28D4 covers the circuit of the three motor phases for clutch B in general and is mainly logged when the controller energises a phase and no current returns, meaning the path is broken. Getrag chose brushless ferrite motors without rare earths for this pump-actuator generation and reused them from the 6DCT250; if one winding path is lost, the remaining two cannot turn the rotor smoothly, and the gerotor pump of clutch B stops delivering oil to the clutch piston. Loose crimp terminals, a fractured wire near the actuator, or an internal connection cracked by heat cycles are the usual finds. P28D2/P28D3 describe phases forced low or high; P28C6 is the same fault on clutch A. No manufacturer has published P28D4 details.

Likely causes

Loose or spread crimp terminal on a clutch B motor phase
Phase wire fractured close to the clutch B actuator
Internal winding joint in the clutch B motor cracked by thermal cycling

Symptoms

  • Clutch B cannot be closed, its gears are blocked
  • Fault may appear only on rough roads or when hot
  • Transmission warning, MIL depending on make

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–1,300
Time0.5–3.5 h

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

Parts involved

clutch motor bwiring harnesstcm

Related codes

P28D2P28D3P28D5P28C6

References: law.cornell.edu, cti-symposium.world, static.nhtsa.gov.