Powertrain, generic (extended)

P28D3 Clutch B Motor Phase U-V-W Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P28D3 is the high-voltage fault on the phase wiring of the clutch B motor: a lead reads above what the inverter pattern should produce, typically because it contacts a positive feed or the upper switch cannot turn off. In the Getrag 7DCT300 five brushless motors share the housing, two for the shift drums, two for the clutch pumps and one for the cooling pump, so motor harnesses run close together and a chafed spot can bridge to a neighbouring supply. Pin corrosion in the connector is a further candidate. P28D2 is the ground-side fault, P28D4 the interruption, and P28C5 the matching clutch A code. Values are not public. The transmission controller usually disables clutch B and drives on the other half.

Likely causes

Clutch B motor phase touching a neighbouring positive feed in the harness
Corroded pins bridging at the clutch B motor connector
Upper output switch for the clutch B motor stays conducting

Symptoms

  • Warning lamp and stored fault code
  • Vehicle drives on with only one clutch, gear choice reduced
  • Possible jerk when the controller drops clutch B

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,300
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

P28D2P28D4P28D5P28C5

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