P2D97 — Starter/Generator Phase Z Current Sensor Circuit Low

Diagnostic algorithm

1. Retrieve freeze-frame and live sensor data; note when the low reading occurs (idle, cranking, load).
2. Verify battery/system voltage is normal. Low system voltage can cause false low sensor readings.
3. Visually inspect the phase Z sensor, connector, and wiring harness for damage, corrosion or poor pins. Repair visible problems.
4. With connector connected, back-probe the sensor pins and measure: a) reference/supply voltage, b) ground continuity, c) sensor output voltage at rest and while cranking/under load. Compare to expected values and to other phase sensors.
5. Use an oscilloscope or high-resolution data logger to observe the sensor waveform during generator operation; look for clipped, stuck-low, noisy or absent signals.
6. If sensor output is stuck low and supply/ground are correct, disconnect the sensor and check for short to ground on the output wire (measure resistance to ground and to module).
7. Check continuity from sensor connector back to the control module; repair any opens or shorts. Inspect intermediate connectors and grounds.
8. If wiring and connectors are good but the sensor remains out of range, replace the phase Z current sensor (or starter/generator assembly if sensor is integral).
9. If new sensor does not clear the code, suspect the control module — consult wiring diagrams and consider module bench testing or replacement per manufacturer procedures.
10. After repairs, clear the code and perform a functional test (charge/regeneration and a road or dyno test) to confirm the fault does not return.