Powertrain, generic · Hybrid propulsion

P0B05 Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B05 flags overcurrent in phase V of the electric auxiliary transmission fluid pump motor. No manufacturer publicly documents this specific code. GM monitors the same physical fault without naming the phase: P0C28 trips when any of U, V or W exceeds 35 A for about 10 ms within a 62 ms window, and a 2018 Cadillac CT6 plug-in service update shows how a faulty pump restart routine alone can push the current over that limit. Likely triggers for a V-specific high code are a short in the V lead, shorted turns, a seized or contaminated pump, or a restart against a stalled rotor. The Hitachi patent on sub-oil pump drives shows the phase currents come from a shared sensor. Auto-stop is usually blocked. P0B04 is the low side, P0B02 and P0B08 phases U and W.

Likely causes

Phase V lead shorted to another phase or to ground
Pump seized or contaminated, motor draws excess current
Pump restart logic in the inverter software causing overcurrent
Shorted turns in phase V of the pump motor

Symptoms

  • MIL and transmission or hybrid warning
  • Loss of propulsion or no-start in severe cases

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,500
Time0.5–6 h

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

Parts involved

aux trans pump motor phase vaux trans pump control modulewiring harness

Related codes

P0B02P0B03P0B04P0B08P0C22P0C28

References: gsi.ext.gm.com, static.nhtsa.gov, patents.google.com.