Powertrain, generic (extended)

P2D9C Starter/Generator Phase V Current Circuit Intermittent/Erratic

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P2D9C reports an erratic current signal on phase V of the starter/generator. V is the phase that some designs never measure: in a star-connected three-phase winding the three currents add up to zero, so GM's eAssist table runs sensor checks only on U and W. Other inverters fit a sensor to every phase conductor, often a Hall chip in a ring core whose output voltage follows the current. A system that stores P2D9C therefore evaluates phase V on its own, and an unsteady value there leads to the V sensor, its plug or its leads rather than to the other two phases. No manufacturer documents P2D9C publicly. Drivers notice a sporadic warning and short gaps in stop-start or boost. Neighbours: P2D9B (U) and P2D9D (W).

Likely causes

Phase V sensor plug not fully latched or with fretting corrosion
Intermittent break in the phase V sensor wiring
Phase V current sensor with unstable output

Symptoms

  • Sporadic system warning on the instrument cluster
  • Short interruptions of stop-start or boost

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–2,000
Time0.5–5 h

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

Parts involved

starter generator phase v current sensorwiring harnessstarter generator control module

Related codes

P2D9BP2D9DP2D99P0BE9P0BEA

References: gsi.ext.gm.com, powersystemsdesign.com.