P0A45 means the ECU has detected a **range or performance problem in the Drive Motor “B” temperature sensor circuit**, which monitors the operating temperature of the secondary traction motor (commonly the rear motor on e-AWD hybrids and EVs). A range/performance fault means the sensor is reading temperatures that don’t match real operating conditions — values rising too fast, too slow, or sitting outside the logical thermal profile for the rear motor. When this signal becomes unreliable, the ECU may disable AWD, limit torque, or enter limp mode. This guide explains what P0A45 means, the symptoms, causes, diagnostic steps, and repair options.
What Does P0A45 Mean?
P0A45 sets when the Hybrid/EV Powertrain Control Module sees **sensor behavior that is electrically intact but logically incorrect**. The voltage may fall within the acceptable electrical range, but the temperature pattern does not match expected values based on motor load, inverter heat, coolant temperature, or driving conditions.
This is different from pure electrical faults like P0A44, P0A46, or P0A47. Instead, the thermistor inside the motor may be drifting, contaminated, or responding abnormally, leading to inconsistent thermal feedback the ECU cannot trust.
Quick Reference
- OBD-II Family: P-Code (Hybrid/EV Powertrain)
- Scope: Generic
- System: Drive Motor “B” Temperature Monitoring
- Difficulty Level: Moderate
- Estimated Repair Cost: €150–€500
- Last Updated: 2025-11-24
Real-World Example / Field Notes
This code shows up often on Toyota e-AWD hybrids, Lexus AWD hybrids, Hyundai Ioniq/EV6 dual-motor EVs, and GM/Voltec systems. In a Toyota Highlander Hybrid AWD, the rear motor temperature would rise extremely slowly even during steep hill climbs. The problem was coolant contamination on the thermistor housing, insulating it from actual heat and delaying its response. On a Kia EV6, P0A45 occurred because the rear inverter coolant pump was weak, causing sudden temperature spikes that looked like sensor failure until airflow and coolant flow were tested.
Symptoms of P0A45
- Unrealistic temperature trends: Rising too slowly or too quickly.
- AWD disabled: Vehicle may run in FWD only.
- Reduced EV torque: Rear motor may cut out under load.
- EV mode dropout: Hybrids rely more heavily on the engine.
- Limp mode: Power reductions during acceleration.
- Warning indicators: “EV System Malfunction,” “AWD Malfunction,” or similar messages.
- Cooling system overactivity: Pump and fans may run at full speed.
Common Causes of P0A45
Most Common Causes
- Thermistor drift — sensor values no longer respond correctly.
- Sensor contamination by coolant, oil, or debris.
- Rear motor cooling restriction causing unrealistic heat patterns.
- Weak or intermittent inverter pump affecting temperature rates.
- Incorrect correlation between motor and inverter temperature readings.
Less Common Causes
- Loose, oxidized, or partially failing sensor connector.
- Intermittent wiring resistance changes from corrosion.
- Internal stator temperature circuit damage.
- ECU misinterpretation of thermal profile (rare).
Diagnosis: Step-by-Step Guide
Your objective is to determine whether the temperature sensor is reporting illogical behavior or if the cooling system is creating abnormal temperature changes.
Tools You’ll Need: EV-capable scan tool, multimeter, IR thermometer, wiring diagram, coolant testing tools, optional oscilloscope.
- Check live data patterns. Compare Drive Motor “B” temp with inverter and coolant temp under different loads.
- Look for slow/fast imbalance. A drifting sensor often lags or spikes compared to expected heat generation.
- Inspect the connector. Look for coolant residue, corrosion, or loose locking tabs.
- Check for coolant flow issues. Rear-motor heat spikes may be due to system restrictions, not sensor failure.
- Monitor pump activation with active tests. Weak pumps cause unpredictable temperature trends.
- Perform an IR comparison. Check the rear motor housing temp with an IR thermometer to confirm sensor accuracy.
- Test sensor resistance at ambient temp. Drifted thermistors may test out of spec.
- Inspect rear inverter cooling hoses. Kinks or partial blockages distort heat behavior.
- Review freeze-frame data. Identify whether the fault occurs during acceleration, regen braking, or steady cruising.
- Check for related cooling codes. Codes like P0A93 or P0A94 point to real overheating rather than sensor failure.
Pro Tip: If Drive Motor “B” temperature rises slower than inverter temperature under high load, inspect the sensor for contamination — especially coolant film, which acts like insulation and delays heat transfer.
Possible Fixes & Repair Costs
- Replace Drive Motor “B” temperature sensor (if serviceable): €150–€300.
- Fix contamination on sensor housing: €20–€60.
- Repair or replace weak coolant pump: €120–€350.
- Restore cooling flow: €40–€200 (hoses, blockages, air pockets).
- Repair wiring or connector corrosion: €10–€100.
- Repair stator temperature circuit (if internal): €300–€500+.
Always compare live thermal behavior with actual motor temperature before replacing expensive components. Many P0A45 faults come from cooling issues, not sensor failure.
Can I Still Drive With P0A45?
The car may still drive, but rear-motor torque limits or AWD shutdown can occur suddenly. If the temperature reading is unreliable, the ECU will reduce power to protect the motor. Avoid long trips or heavy loads until the issue is diagnosed and repaired.
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
- P0A45 indicates unrealistic or inconsistent Drive Motor “B” temperature sensor readings.
- Sensor drift, contamination, or cooling restrictions are the most common causes.
- The ECU may disable AWD or reduce torque to prevent overheating.
- Live-data analysis is essential for accurate diagnosis.
FAQ
What causes P0A45 most often?
A drifting or contaminated thermistor, inconsistent cooling flow, or weak inverter coolant pump can all create unrealistic temperature behavior.
How is P0A45 different from P0A44 or P0A46?
P0A45 is a performance fault — the sensor is electrically intact but behaving illogically. The others are pure electrical faults (open or short).
Is P0A45 dangerous?
Potentially, because the ECU may disable AWD or cut torque unexpectedly. Incorrect temperatures can lead to real overheating if ignored.
How do I diagnose P0A45?
Compare live data trends with actual motor temperature, inspect connectors, verify coolant flow, and test sensor resistance.
Can I drive with P0A45?
Short trips may be safe, but AWD or torque reduction may occur suddenly. Repair the cause before heavy or high-speed driving.