P0A0A means the ECU has detected a fault in the **Drive Motor “B” Temperature Sensor circuit** — the sensor that monitors the temperature of the secondary electric drive motor in a hybrid or EV (common on dual-motor systems, AWD hybrids, and e-Four setups). When this circuit malfunctions, the ECU cannot determine if Motor “B” is overheating, so it may reduce torque, disable AWD electric drive, or enter protection mode. This guide explains what P0A0A means, the symptoms, causes, diagnostic process, and the repairs that usually fix this high-voltage temperature sensor issue.
What Does P0A0A Mean?
P0A0A sets when the ECU receives an implausible, missing, or unstable signal from the Drive Motor “B” Temperature Sensor. Like Motor “A,” this sensor is almost always an NTC thermistor embedded in or mounted to the electric motor housing. If the voltage signal is out of the expected range — due to wiring problems, sensor failure, or connector corrosion — the ECU will treat the temperature reading as invalid.
Because temperature directly affects torque output and thermal protection of the motor windings and inverter circuitry, the ECU may cut electric drive to Motor “B,” disable electric AWD, or switch to front-wheel-only operation until the fault is resolved.
Quick Reference
- OBD-II Family: P-Code (Hybrid/EV Powertrain)
- Scope: Generic
- System: Drive Motor “B” Temperature Monitoring
- Difficulty Level: Moderate to High
- Estimated Repair Cost: €80–€400
- Last Updated: 2025-11-24
Real-World Example / Field Notes
P0A0A is common on vehicles with dual electric motors such as Toyota/Lexus e-Four AWD hybrids, Hyundai/Kia PHEVs with rear EV modules, and some GM and Nissan dual-motor EVs. One Lexus NX300h case showed loss of rear electric drive during slippery conditions. Live data displayed Drive Motor “B” temperature stuck at –40°C — a classic open-circuit indicator. The cause was water intrusion into the rear motor connector after winter road salt caused corrosion. Cleaning the connector and replacing the pigtail restored AWD electric functionality. On Hyundai PHEVs, wiring near the rear differential is prone to chafing, often triggering P0A0A.
Symptoms of P0A0A
- Rear electric motor not engaging: AWD hybrid/EV systems may drop to FWD only.
- Reduced electric power: ECU limits torque from Motor “B.”
- Limp mode: Vehicle may limit acceleration or block EV-only operation.
- Warning lights: “EV System Error,” “Check Hybrid System,” or “AWD System Malfunction.”
- Cooling fan activation: ECU compensates for missing temperature data.
- Unrealistic temperature readings: –40°C, 150°C+, or erratic jumps.
- Check Engine Light: Code often appears with inverter or motor control DTCs.
Common Causes of P0A0A
Most Common Causes
- Failed Drive Motor “B” temperature sensor.
- Open circuit from broken wiring or unplugged connector.
- Corroded pins due to road-spray moisture (common on rear-mounted motors).
- Short-to-ground or short-to-power in the harness.
- Moisture or oil intrusion inside the connector.
Less Common Causes
- Actual overheating due to cooling system issues (liquid-cooled motors).
- Air pockets in the cooling jacket causing misinformation.
- ECU internal input circuit faults (rare).
- Incorrect coolant type reducing sensor accuracy.
- Sensor not seated properly or poor thermal contact.
Diagnosis: Step-by-Step Guide
Your goal is to determine whether the sensor, wiring, connector, or cooling system is causing invalid or unstable Motor “B” temperature data.
Tools You’ll Need: EV/hybrid-capable OBD-II scanner, multimeter, wiring diagram, IR thermometer, cooling system tools (if liquid-cooled), and underbody inspection equipment.
- Check live data for Motor “B” temperature. Look for impossible values like –40°C (open circuit) or 150°C+ (short-to-ground).
- Inspect the connector. Rear motors are exposed — corrosion and moisture are extremely common.
- Perform a wiggle test. Flex the harness while watching live data. Sudden jumps indicate an intermittent connection.
- Check wiring for external damage. Look for chafed insulation, crushed cables, or salt corrosion along the chassis.
- Test sensor resistance. Measure and compare to OEM temperature/resistance charts.
- Check for open circuit. Use a multimeter to test continuity from the sensor to the ECU.
- Test for short-to-ground or battery. Unexpected grounding or 12v reference intrusion will distort readings.
- Compare with IR thermometer readings. If live data is unstable but casing temperature is steady, the circuit is failing.
- Inspect cooling system (if applicable). Low coolant or blocked passages can cause real temperature instability.
- Scan for companion codes. P0A2F, P0A07–P0A09, or inverter pump codes help narrow down root cause.
Pro Tip: On AWD hybrids, Motor “B” temperature sensors often sit low near the rear differential. If the temperature reading jumps during pothole impacts or speed bumps, suspect a broken internal wire or corroded connector pin.
Possible Fixes & Repair Costs
- Repair or replace damaged wiring: €10–€100.
- Clean or replace corroded connector terminals: €10–€50.
- Replace Drive Motor “B” Temperature Sensor: €90–€200.
- Fix coolant leaks (if liquid-cooled): €20–€120.
- Bleed or flush motor cooling system: €40–€120.
- Replace coolant pump (if applicable): €100–€350.
Always test wiring and connector integrity before replacing the sensor — most P0A0A faults are caused by environmental damage rather than internal sensor failure.
Can I Still Drive With P0A0A?
Driving with P0A0A is possible but risky. The ECU may disable Motor “B,” reducing AWD capability and limiting torque — especially important in snow or aggressive acceleration. Sudden power loss to the rear motor can occur. Repair this issue promptly to restore full hybrid/EV performance and prevent overheating damage.
Related Codes
- P0A6C – Hybrid Battery Voltage System Isolation Sensor Range/Performance
- P0A9F – Hybrid Battery Temperature Sensor Too Hot
- P0A9E – Hybrid Battery Temperature Sensor Too Cold
- P0A9D – Hybrid Battery Temperature Sensor Range/Performance
- P0A9C – Motor Electronics Coolant Temperature Sensor Circuit High
- P0A9B – Motor Electronics Coolant Temperature Sensor Circuit Low
- P0A9A – Motor Electronics Coolant Temperature Sensor Circuit Range/Performance
- P0A99 – Motor Electronics Coolant Temperature Sensor Circuit
- P0A98 – Hybrid Battery Pack Cooling Fan 2 Performance
- P0A97 – Hybrid Battery Pack Cooling Fan 2 Control Circuit
Key Takeaways
- P0A0A indicates a Drive Motor “B” temperature sensor circuit malfunction.
- Most causes involve corrosion, open circuits, or wiring damage.
- Driving may be possible, but electric AWD may be disabled.
- Live data and connector inspection are crucial for accurate diagnosis.
FAQ
What causes P0A0A most often?
Corroded connectors or broken wiring near the rear motor are the most common causes, especially in vehicles exposed to road salt and moisture.
Is P0A0A serious?
Yes. Incorrect Motor “B” temperature data can cause torque reduction, AWD loss, or overheating risks if the motor is actually hot.
Does P0A0A always affect AWD?
On models with rear electric motors, yes — the ECU will normally disable rear-motor torque until temperature readings are reliable.
How do I diagnose this code?
Monitor live data, inspect connectors for corrosion, test resistance, check wiring continuity, and compare temperature readings to IR measurements.
Can I keep driving with P0A0A?
Short distances may be okay, but sudden loss of rear electric drive or overheating protection can occur. Repair quickly for safe operation.