What it means
The control module monitors generator position sensor circuit A for an electrical fault that prevents it from receiving a usable signal. It sets this code when the circuit does not meet its expected electrical conditions.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Generator position sensors report rotor position so the hybrid or electric drive control system can time motor and generator operation. The module monitors circuit A for an electrical fault that prevents it from getting a usable position signal and sets P0C64 when the circuit fails its electrical checks.
Common causes
Most likely first.
- Position sensor failed
- Wiring fault
How to diagnose it
- Read stored and pending codes and freeze-frame data to see when the circuit A fault occurred and whether related hybrid-system codes are present.
- With the vehicle powered down as specified by the manufacturer, inspect the circuit A sensor connector and harness for loose connections, damage, corrosion, or fluid intrusion.
- Check the sensor's specified power, ground, and signal connections using the manufacturer's wiring information, looking for a supply or ground failure that could disrupt circuit A.
- Measure circuit A continuity and check for shorts between its wires and to ground or power, isolating the sensor and control module as directed by the manufacturer's procedure.
- If wiring checks pass, test the circuit A position sensor and its signal against the manufacturer's specification to distinguish a failed sensor from a harness or module fault.
Common fixes
- Reconnect and secure a loose circuit A sensor connector.
- Repair damaged or corroded circuit A wiring or connector terminals.
- Restore a failed circuit A power or ground connection.
- Replace the generator position sensor if it fails the specified test.
Can I keep driving?
Because this fault can trigger limited operation, avoid relying on the vehicle for longer trips or situations where reduced power would be hazardous. If a hybrid or EV warning or reduced power appears, stop somewhere safe and arrange diagnosis; continued operation may leave the vehicle unable to provide normal drive power.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.