P2D99Starter/Generator Phase Y Current Circuit Intermittent/Erratic
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- P2D99 is stored when the phase Y current value of the starter/generator behaves in a way a real winding current cannot: sudden steps, dropouts to zero or noise between consecutive samples. The winding inductance smooths the true current, so such jumps implicate the measuring path. Only systems that actually sense phase Y can raise this code; GM's eAssist table, for example, lists current sensor checks for phases U and W alone. Mazda's ISG bulletin 01-004-25 confirms that a starter/generator may carry an X-Y-Z phase group. No manufacturer documents P2D99 publicly. Check the connector for corrosion and pin drag first, then the harness route near hot or moving parts. Steady counterparts: P2D93 (high), P2D96 (low), P2DC3 (circuit); X and Z intermittent: P2D98, P2D9A.
- What you may notice
- Sporadic hybrid or charging system warning
- Recuperation occasionally interrupted
- Likely causes
- LikelyCorrosion or weak pin tension in the phase Y sensor connector
- PossibleHarness damaged by heat from the exhaust side or by contact with moving parts
- RarePhase Y current sensor producing a noisy or unstable signal
- 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: €100 – €2,000
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.