P2DC4Starter/Generator Phase Y Current Sensor Circuit Range/Performance
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2DC4 says the phase Y current reading of the starter/generator is inside its electrical limits but fails a plausibility test. One way to test it is an energy balance: the power drawn or delivered on the phase side must match the current on the DC side. GM's eAssist machine compares the sum derived from its phase sensors with the DC-DC converter input and battery pack current; a gap above 40 A in 90 of 96 checks, run every 2.08 ms, sets a two-trip Type B code, and current control then continues without the sensors. GM measures U and W only, so this is an analogue, not P2DC4 itself, which no manufacturer documents publicly. A sensor with a gain error or a drifting zero is the usual suspect. Circuit: P2DC3; X and Z range: P2DC2, P2DC6.
- What you may notice
- Warning lamp after two trips with the fault
- Noticeably weaker boost and smoother but slower restarts
- Likely causes
- LikelyPhase Y current sensor reading consistently too high or too low
- PossibleZero offset of the phase Y sensor drifted
- RareComparison value wrong because the DC-side current measurement is faulty
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €150 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.