P0A57

What it means

P0A57 is a generic hybrid/electric vehicle code meaning the control unit sees the signal from the Drive Motor B current sensor as lower than its expected range. The motor control unit uses this sensor to measure phase current and control torque. A reading stuck low, or out of range, makes the unit distrust the measurement and set the code. Where the sensor sits and how it is built depends on the model and drive system.

Symptoms

• Hybrid or EV system warning light on the dashboard
• Reduced power or limp-home mode
• Poor or jerky acceleration
• Engine not starting or stopping as normal on a hybrid
• Vehicle refusing to enter Ready mode in some cases

Possible causes

• Wiring or connector fault in the Drive Motor B current sensor circuit (open circuit, short to ground, corrosion or poor pin tension)likely
• Faulty Drive Motor B current sensor or its internal sensing elementlikely
• Low or unstable sensor reference or supply voltage to the sensorpossible
• Fault within the inverter or motor control module that processes the sensor signalpossible
• Low 12 V battery voltage or poor earths causing false sensor readingspossible
• Damage to high-voltage cables or connections affecting current measurementrare

How to diagnose

1. Read all stored and pending codes and record the freeze frame data, noting vehicle speed, motor state and battery voltage when the code set.
2. Check the 12 V battery condition and charging, and look for any other low-voltage or communication codes that could point to a shared cause.
3. Check for manufacturer service bulletins or known issues for this model and drive system.
4. Visually inspect the Drive Motor B current sensor wiring and connectors for chafing, water ingress, corrosion and loose pins. Do not touch orange high-voltage cabling unless qualified.
5. Using live data, compare the Drive Motor B current reading with the motor's actual state. A value stuck low or at zero when the motor is working points to the sensor or circuit.
6. Following the manufacturer's procedure, check the sensor's supply voltage, signal and earth for continuity and shorts. This must only be done once the high-voltage system is shut down and made safe by a qualified person.
7. Clear the code and road test, watching live data to see if the fault returns and under what conditions.

How to fix

• Repair or replace damaged wiring, and clean or replace corroded or loose connectors in the sensor circuit.
• Replace the Drive Motor B current sensor, or the assembly it is part of, if it is confirmed faulty and the manufacturer allows it.
• Restore correct supply and earth to the sensor by repairing the circuit fault found.
• Repair or replace the inverter or motor control module if the signal is proven good at the sensor but wrongly read, following manufacturer procedure.
• Replace or recharge a weak 12 V battery and repair poor earths if low voltage is causing the fault.

Can I keep driving?

Nearby codes

• P0A56GenericDrive Motor B Current Sensor Circuit Range/Performance
• P0A58GenericDrive Motor B Current Sensor Circuit High