Powertrain, generic (extended)

P2DCB Starter/Generator Phase X-Y-Z Current Sensor Correlation

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P2DCB compares the three current sensors of the starter/generator's X-Y-Z phase group with one another or with the DC side. In a star-connected winding the instantaneous phase currents must add up to roughly zero; if they do not, at least one sensor is wrong, even though each may sit inside its own limits. Mazda's bulletin 01-004-25 shows that an integrated starter generator can carry a second stator driver group called X, Y and Z beside U, V and W. GM's eAssist instead balances currents: if the value derived from the phase sensors differs from DC-DC converter plus battery pack current by more than 40 A in at least 90 out of 96 checks, one every 2.08 ms, P0BFD sets as Type B and current control runs without sensors within 187.2 ms. No manufacturer documents P2DCB publicly. Single-sensor faults: P2DC1 to P2DC6.

Likely causes

Gain or zero drift of one phase current sensor

Disturbed supply or reference voltage shared by the sensors

Calibration or software fault in the starter/generator controller

Symptoms

Check engine light with hybrid or 48 V system warning
Reduced electric boost and recuperation in substitute mode
Start-stop may be disabled

Repair estimate

DifficultyHardWorkshop job

Parts and labour€150–2,500

Time1–4 h

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

Parts involved

starter generator phase x current sensorstarter generator phase y current sensorstarter generator phase z current sensorstarter generator control module

References: gsi.ext.gm.com, static.nhtsa.gov, law.cornell.edu.