P0A49

What it means

P0A49 is a generic hybrid and electric vehicle code meaning the control unit has detected an intermittent fault in the position sensor circuit for drive motor B. The motor control module saw the rotor position signal drop out, glitch or go implausible from time to time rather than fail permanently. Without a reliable rotor position, the motor cannot be controlled accurately, so the system may limit power or shut down the motor.

Symptoms

• Hybrid or electric system warning light on, possibly with the main warning light
• Intermittent loss of power or reduced performance mode
• Jerky or rough drive, or hesitation when pulling away
• Engine starting or stopping unexpectedly on a hybrid, or failure to enter ready mode
• Fault appearing and clearing on its own, often linked to bumps, heat or vibration
• Vehicle shutting down the drive system while moving in some cases

Possible causes

• Damaged, chafed or intermittently open-circuit wiring between the motor position sensor and the motor control unitlikely
• Loose, corroded or contaminated connector terminals at the motor position sensor or control unitlikely
• Faulty drive motor B position sensor (resolver or equivalent) with an intermittent internal faultpossible
• Electrical interference or poor shielding or earth on the sensor circuit, for example from a damaged high-voltage cable nearbypossible
• Moisture or coolant or oil ingress into the sensor or connectorpossible
• Faulty motor control unit or inverter electronicsrare
• Mechanical damage or a mounting problem affecting sensor alignment at the motorrare

How to diagnose

1. Read all stored and pending codes and the freeze frame data, noting speed, temperature, load and whether other motor or inverter codes are present
2. Check for manufacturer service bulletins or known issues for the specific model and motor layout, as the location of motor B varies
3. Visually inspect the sensor wiring and connectors for chafing, heat damage, corrosion, moisture and bent or pushed-back pins, following the manufacturer's high-voltage safety procedure first
4. With the vehicle's high-voltage system made safe, carry out a wiggle test on the harness and connector while monitoring live rotor position data for dropouts
5. Check the sensor circuit for continuity, shorts to earth or voltage, and resistance of the sensor windings against the manufacturer's specification
6. Check shielding and earth connections on the sensor circuit and inspect nearby high-voltage cabling for damage
7. Inspect the motor housing area for coolant or oil leaks and moisture reaching the sensor
8. If the wiring and sensor test fine, check the control unit's power and earths before considering unit replacement

How to fix

• Repair or replace damaged wiring sections, using the correct type of cable and restoring any shielding
• Clean, repair or replace faulty connector terminals and seal the connector against moisture
• Replace the drive motor position sensor or the motor assembly part that contains it, as the manufacturer specifies
• Repair earth or shielding faults and replace any damaged cabling causing interference
• Cure any fluid leak and dry or replace affected components
• Replace or reprogram the motor control unit or inverter only after the circuit and sensor are proven good, and only where the manufacturer confirms it

Can I keep driving?

Nearby codes

• P0A48GenericDrive Motor B Position Sensor Circuit High
• P0A4AGenericDrive Motor B Position Sensor Circuit Overspeed