P0A46 means the ECU has detected a **low-voltage condition in the Drive Motor “B” temperature sensor circuit**, the sensor responsible for monitoring the rear or secondary traction motor’s temperature on dual-motor hybrids and EVs. “Circuit Low” indicates the signal voltage has dropped below the valid range — usually caused by a short-to-ground, internally shorted thermistor, or wiring damage. When this happens, the ECU cannot trust the temperature reading and may disable AWD, reduce torque, or enter limp mode to prevent unnoticed overheating. This guide explains the meaning, causes, symptoms, diagnosis, and repair options for P0A46.
What Does P0A46 Mean?
P0A46 sets when the Hybrid/EV Powertrain Control Module sees **voltage from the Drive Motor “B” temperature sensor that is lower than the acceptable operating threshold**. These temperature sensors use NTC thermistors. Low voltage corresponds to very high temperature, so when the signal drops too low, the ECU interprets it as an overheating condition or a circuit short.
To protect the rear motor (Drive Motor B), the ECU may disable AWD, reduce EV torque output, or trigger warning messages whenever the temperature signal cannot be trusted.
Quick Reference
- OBD-II Family: P-Code (Hybrid/EV Powertrain)
- Scope: Generic
- System: Drive Motor “B” Temperature Monitoring
- Difficulty Level: Moderate
- Estimated Repair Cost: €120–€400
- Last Updated: 2025-11-24
Real-World Example / Field Notes
P0A46 is seen frequently on Toyota/Lexus e-AWD hybrids, Hyundai/Kia dual-motor EVs, and GM/Voltec platforms. In a Toyota RAV4 Hybrid AWD, the rear motor temperature spiked instantly to 150°C on key-on. The cause was water intrusion inside the sensor connector, shorting the signal pin to ground. In a Hyundai Kona Electric, an internal thermistor failure caused the sensor to read extremely high temperature only during hard acceleration — a tricky intermittent short that required live-data graphing to identify.
Symptoms of P0A46
- Fixed high temperature reading: Often 130–150°C at all times.
- AWD or rear motor disabled: Vehicle may default to FWD.
- Reduced EV torque: Heavy load may trigger further torque cut.
- Limp mode: Noticeable power reduction during acceleration.
- Warning messages: “AWD Malfunction,” “EV System Error,” “Check Hybrid System.”
- Cooling components running excessively: Pump and fans may run at high speed.
- Startup hesitation: Severe faults may affect READY-mode entry.
Common Causes of P0A46
Most Common Causes
- Short-to-ground on the temperature sensor signal wire.
- Failed NTC thermistor inside Drive Motor “B.”
- Water or coolant intrusion inside the sensor connector.
- Chafed wiring near the rear subframe or inverter area.
- Contaminated connector terminals creating a low-voltage path.
Less Common Causes
- Harness corrosion from road salt exposure.
- Intermittent internal stator temperature circuit shorts.
- Failing ground reference or ECU signal driver (rare).
- Severe inverter overheating (may accompany performance codes).
Diagnosis: Step-by-Step Guide
Your goal is to find where the low-voltage condition originates — wiring, connector, or a failing thermistor.
Tools You’ll Need: EV-ready scan tool, multimeter, wiring diagram, IR thermometer, coolant tools, optional oscilloscope.
- Check live temperature data. A fixed reading near maximum (140–150°C) strongly suggests a short-to-ground.
- Inspect the connector. Look for moisture, coolant residue, corrosion, or loose terminals.
- Perform a harness wiggle test. Watch live data as you move the harness — sudden jumps confirm wiring shorts.
- Measure signal voltage. If voltage is very low at the connector, the circuit is being pulled to ground.
- Check sensor resistance at ambient temperature. A bad thermistor often shows near-zero resistance (shorted internally).
- Test continuity to ground. If the signal wire has continuity to ground, trace the harness for insulation damage.
- Inspect harness routing under the vehicle. Damage is common near clips, brackets, or sharp edges.
- Verify actual motor temperature. Compare scan-tool data with IR readings to confirm false high readings.
- Review freeze-frame data. This shows whether the fault occurs at startup, under load, or during regen braking.
- Check rear cooling flow. Cooling system restrictions don’t typically trigger P0A46, but they can speed up sensor failure.
Pro Tip: If Drive Motor “B” temperature jumps to maximum the moment the vehicle enters READY mode, the most likely cause is a grounded signal circuit — typically wiring damage or moisture intrusion.
Possible Fixes & Repair Costs
- Repair grounded or shorted wiring: €20–€120.
- Clean or replace contaminated connectors: €10–€50.
- Replace Drive Motor “B” temperature sensor (if serviceable): €150–€300.
- Repair or replace internal motor thermistor circuit: €300–€500+ depending on model.
- Fix coolant leaks around the connector area: €40–€150.
- Bleed/restore inverter cooling system flow: €40–€120.
Always verify the wiring first — short-to-ground conditions are far more common than internal motor failures.
Can I Still Drive With P0A46?
Driving may be possible, but AWD or rear-motor torque can drop out suddenly. Because the ECU sees what looks like extreme overheating, it will reduce torque to protect the motor. If the temperature display is stuck at maximum or warnings appear, avoid driving until the fault is corrected.
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
- P0A46 indicates a low-voltage fault in Drive Motor “B” temperature sensing.
- Short-to-ground wiring, moisture intrusion, or a failed thermistor are the most common causes.
- AWD or rear-motor torque may be disabled to protect the motor.
- Fixed high-temperature readings are a major diagnostic clue.
FAQ
What causes P0A46 most often?
Usually a short-to-ground in the signal circuit or a thermistor that has failed internally and is reading extremely low resistance.
Why does the temperature show extremely high values?
Because low signal voltage mimics an overheating condition, often caused by a grounded wire or contaminated connector.
Is P0A46 dangerous?
It can be. The ECU may disable AWD or significantly reduce power, and real overheating could go unnoticed if the sensor is faulty.
How do I diagnose P0A46?
Inspect the connector, test for ground faults, monitor live data, check wiring continuity, and measure sensor resistance at ambient temperature.
Can I drive with P0A46?
Short distances may be possible, but sudden torque reduction is likely. Repair the issue before resuming normal driving.