Powertrain, generic (extended)

P2D93 Starter/Generator Phase Y Current Sensor Circuit High

Check engine lightOn

EmissionsRelevant

Drive cycleNot required

Limp modePossible

P2D93 reports that the current reading for phase Y of the starter/generator has climbed past its upper validity limit. Y is the middle letter of the X/Y/Z set this code series uses; the same list also has U/V/W variants (P2D9B to P2D9D), and no maker explains publicly how it assigns them. Not every design measures every phase. GM's eAssist belt system lists sensor circuit checks only for phases U and W, since with three phases one current can be calculated from the other two. A system that stores P2D93 therefore has a dedicated sensor on Y. No manufacturer documents this code publicly. Real phase currents do not get that high, so suspect a shorted signal lead, the sensor itself or the control module. P2D96 is the low fault, P2DC3 the general Y circuit code, P2DC4 the range check.

Likely causes

Phase Y sensor signal lead chafed and touching a voltage-carrying wire

Internal fault of the phase Y current sensor in the machine electronics

Defective input stage in the starter/generator control module

Symptoms

Hybrid or charging system warning on the instrument cluster
Boost function during acceleration missing or reduced
Engine restarts by the conventional starter or not at all after auto stop

Repair estimate

DifficultyHardWorkshop job

Parts and labour€150–2,000

Time0.5–4 h

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

Parts involved

starter generator phase y current sensorwiring harnessstarter generator control module

References: gsi.ext.gm.com, law.cornell.edu.