What it means
The current measurement on starter/generator phase U drops out or jumps intermittently. Loose connector or vibration-sensitive sensor.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The starter/generator uses phase U as one of its electrical current paths while providing engine starting, hybrid assist, or energy recovery. The control module monitors the phase U current signal and sets this code when it becomes erratic or drops out intermittently.
Common causes
Most likely first.
- Sensor connector not seated
- Harness chafing intermittently shorts the wire
- Connector with intermittent contact under vibration
Symptoms
- Check-engine or hybrid-system warning light may be on
- Intermittent reduction in hybrid assist or regenerative charging
- Engine starting or stop-start operation may be inconsistent
How to diagnose it
- Check freeze-frame data and live phase U current readings for dropouts, and compare them with the other phase readings under the same operating conditions.
- With the system safely powered down according to the vehicle procedure, inspect the phase U sensor connector for incomplete seating, damaged pins, corrosion, or moisture.
- Trace the phase U wiring for chafing, pinching, or contact with hot or moving parts that could cause an intermittent short.
- Check connector and harness continuity while gently moving the wiring, following the manufacturer's procedure, to reveal vibration-sensitive contact loss.
- If the wiring and connections are sound, test the phase U current sensor and related module inputs against the manufacturer's specification.
Common fixes
- Reseat and secure the phase U current-sensor connector.
- Repair chafed or damaged phase U wiring and restore its routing and protection.
- Repair or replace terminals that have poor or intermittent contact.
- Replace the phase U current sensor if testing confirms it is faulty.
Can I keep driving?
Avoid relying on hybrid assist or regenerative charging, and limit driving if starting or stop-start operation becomes unreliable or power is reduced. If the vehicle enters limited operation or displays a hybrid-system warning, stop somewhere safe and arrange diagnosis.
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.