P0A44

What it means

P0A44 means the hybrid or EV control system has flagged a fault on the drive motor 'A' position sensor circuit because the motor speed it calculated exceeded the permitted limit. The motor position sensor, often a resolver, tells the inverter or motor control unit how fast the rotor is turning and where it is. The code sets when that signal indicates an impossible or excessive speed, which can be a real overspeed or a corrupted signal.

Symptoms

• Hybrid or EV system warning light or malfunction message on the dash
• Reduced power or limp-home mode
• Vehicle will not enter Ready mode or shuts down while driving
• Jerky or uneven drive and torque delivery
• Engine running more than normal in a hybrid as the motor is restricted
• Other drive motor or inverter codes stored alongside

Possible causes

• Noisy or corrupted position sensor signal from damaged wiring, poor shielding or a poor earthlikely
• Corroded, loose or contaminated connector at the motor position sensor or inverterlikely
• Faulty drive motor position sensor (resolver or equivalent)possible
• Fault in the inverter or motor control unit's sensor interface or processingpossible
• Genuine overspeed event, such as a driven wheel losing grip or a driveline decoupling fault (depends on model and drivetrain layout)possible
• Low or unstable 12 V supply upsetting control unit readingsrare
• Outdated control unit software where the manufacturer has documented a known faultrare

How to diagnose

1. Read all stored and pending codes and note the freeze frame data, including vehicle speed, motor speed and conditions when the code set.
2. Check for related codes covering the inverter, other motor position sensors, wheel speed or 12 V supply, and deal with those first if present.
3. Check the 12 V battery condition and charging, as low voltage can cause false faults on hybrid and EV systems.
4. Only if qualified and after following the manufacturer's high voltage isolation procedure, inspect the position sensor wiring and connectors for damage, water, corrosion, bent pins and chafing.
5. Check the sensor wiring for continuity, shorts and shield integrity against the manufacturer's specification, as the values depend on the model.
6. Watch live motor speed and position data during a test, and compare it with vehicle and wheel speed to see if it is a real overspeed or a false signal.
7. Scope the position sensor signal if the manufacturer's procedure allows, looking for dropouts, noise or an incorrect amplitude.
8. Check for available software updates or technical bulletins for the specific model, and for any driveline fault that could allow the motor to overspeed.

How to fix

• Repair or replace damaged wiring, and restore shielding and earth connections.
• Clean, reseat or replace corroded or damaged connectors and terminals.
• Replace the drive motor position sensor, or the motor assembly if the sensor is not serviceable separately, following the manufacturer's procedure.
• Repair or replace the inverter or motor control unit if testing proves an internal fault.
• Update the control unit software only where a manufacturer update addresses a known cause of this fault.
• Correct any driveline or traction fault that allowed a genuine overspeed.

Can I keep driving?

Nearby codes

• P0A43GenericDrive Motor A Position Sensor Circuit Intermittent
• P0A45GenericDrive Motor B Position Sensor Circuit