P0A0C means the ECU has detected a **low-voltage condition** in the Drive Motor “B” Temperature Sensor circuit — the sensor responsible for monitoring the temperature of the secondary electric motor used in AWD hybrids, dual-motor EVs, or e-Four rear-drive units. A “circuit low” fault means the ECU is receiving a voltage that is too low to be realistic, typically caused by a short-to-ground, internal sensor failure, or moisture contamination inside the connector. When this happens, the ECU may disable rear electric torque or limit EV power. This guide explains the meaning, symptoms, causes, diagnosis, and proven fixes for P0A0C.
What Does P0A0C Mean?
P0A0C sets when the ECU sees Drive Motor “B” temperature sensor voltage drop below the expected range. These sensors use NTC thermistors; as temperature rises, resistance falls, causing lower voltage. But if the voltage is *too* low — lower than any valid temperature could produce — the ECU recognizes a circuit fault rather than genuine overheating.
Because accurate temperature data is critical for thermal protection and rear-motor torque management, the ECU may disable Motor “B,” block AWD operation, or activate protection mode until the fault is resolved.
Quick Reference
- OBD-II Family: P-Code (Hybrid/EV Powertrain)
- Scope: Generic
- System: Drive Motor Temperature Monitoring (Motor “B”)
- Difficulty Level: Moderate
- Estimated Repair Cost: €80–€300
- Last Updated: 2025-11-24
Real-World Example / Field Notes
P0A0C appears frequently on Lexus/Toyota e-Four AWD hybrids, Hyundai/Kia PHEVs, and dual-motor EVs. One Toyota RAV4 Hybrid case showed Drive Motor “B” temperature stuck at 150–160°C on a cold start — a textbook short-to-ground condition. Water had entered the rear motor connector after winter driving, creating a conductive path across the signal pin. Cleaning the connector and replacing the sealing gasket solved the issue. On Hyundai Kona EVs, wiring near the rear subframe is known to chafe, causing intermittent shorts and low-voltage temperature signals.
Symptoms of P0A0C
- Rear electric motor disabled: AWD becomes FWD-only.
- Reduced EV torque: ECU limits rear-motor contribution.
- Warning messages: “AWD Malfunction,” “EV System Error,” or “Check Hybrid System.”
- Unrealistic high temperature readings: Often maxed-out values on live data.
- Cooling fans running loudly: ECU reacts as if the motor is overheating.
- Limp mode: Vehicle may reduce acceleration under load.
- Check Engine Light: Often appears alongside inverter or cooling codes.
Common Causes of P0A0C
Most Common Causes
- Short-to-ground in the Motor “B” temperature sensor signal wire.
- Sensor internally shorted (failed thermistor).
- Coolant, oil, or water contamination inside the connector.
- Corroded terminals creating conductive bridges.
- Damaged wiring near the motor or rear subframe.
Less Common Causes
- Actual overheating causing low resistance values.
- Incorrect coolant type affecting thermal conduction.
- ECU input circuit failure (rare).
- Loose connector pin fit creating intermittent grounding.
- Cooling system faults that exaggerate temperature swings.
Diagnosis: Step-by-Step Guide
Your goal is to find where the low voltage originates — sensor, wiring, or contamination.
Tools You’ll Need: EV-capable scan tool, multimeter, IR thermometer, wiring diagram, contact cleaner, and cooling system equipment.
- Check live temperature data. Extreme high values (e.g., 150°C+ on startup) indicate a short-to-ground.
- Inspect the connector. Remove and check for moisture, corrosion, bent pins, or loose locking tabs.
- Perform a wiggle test. Move the harness while monitoring live data to catch intermittent grounding.
- Check for coolant or oil leaks near the connector. Fluids easily create conductive paths.
- Measure sensor resistance. Compare to OEM charts; near-zero resistance indicates internal failure.
- Test for short-to-ground. With the sensor unplugged, check continuity between signal and ground.
- Inspect wiring for chafing. Rear motor harnesses are exposed to road debris and salt.
- Compare with IR thermometer readings. If actual motor temperature is normal, the circuit is faulty.
- Check cooling system (if liquid-cooled). Low coolant or air pockets may cause real overheating spikes.
Pro Tip: If the temperature reading instantly ramps to maximum the moment you turn the car on — cold motor, cold weather — suspect a direct signal-to-ground short or a failed sensor with extremely low internal resistance.
Possible Fixes & Repair Costs
- Repair or replace shorted wiring: €10–€80.
- Replace Drive Motor “B” Temperature Sensor: €80–€200.
- Clean or replace contaminated connector terminals: €10–€50.
- Fix surrounding coolant or oil leaks: €20–€120.
- Bleed or service cooling system: €40–€120.
- Replace coolant pump (if applicable): €100–€350.
Most P0A0C cases are electrical — wiring or connector contamination — so always diagnose these areas before replacing the sensor.
Can I Still Drive With P0A0C?
Driving with P0A0C is possible but risky. The ECU may disable the rear electric motor entirely, reducing AWD traction and EV performance. Sudden torque loss may occur during acceleration. If the reading represents real overheating, further driving could damage the rear motor windings. Repair the issue promptly.
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
- P0A0C indicates a low-voltage (short-to-ground) condition in the Motor “B” temperature sensor circuit.
- Common causes include wiring shorts, sensor failure, and moisture contamination.
- AWD and EV torque may be reduced or disabled during this fault.
- Live data + resistance testing is the fastest way to pinpoint the root cause.
FAQ
What causes P0A0C most often?
Short-to-ground wiring faults, contamination inside the connector, and internally shorted sensors are the top causes.
Why does the temperature reading show extreme high values?
Low circuit voltage mimics extreme overheating in an NTC sensor system, even when the motor is cold.
Is P0A0C dangerous?
It can be. The ECU may disable rear electric drive or limit torque, and if the motor truly is overheating, further driving risks permanent damage.
How do I diagnose P0A0C?
Check live data, inspect connectors, test resistance, perform a wiggle test, and look for grounding faults.
Can I continue driving with P0A0C?
Short trips may be possible, but expect reduced AWD functionality and potential EV power loss. Repair the circuit as soon as possible.