P0A6E means the Hybrid/EV Control ECU has detected a **low-voltage condition in the Motor Electronics Coolant Pump control circuit**. This coolant pump keeps the inverter, motor electronics, and sometimes the electric motor housing properly cooled during operation. A “Circuit Low” fault usually points to a **short-to-ground, excessive current draw, weak power supply, or an internal pump failure**. When the pump cannot run at the commanded level, inverter temperature rises quickly, potentially forcing limp mode or preventing READY mode. This guide explains the meaning, symptoms, causes, diagnosis, and fixes for P0A6E.
What Does P0A6E Mean?
P0A6E sets when the ECU detects that the control signal or feedback line for the inverter coolant pump is **lower than expected**. Depending on the system design, the pump may use a PWM control signal or a feedback circuit that reports motor load and speed. If this voltage drops below specification, the ECU concludes that the pump is either shorted, overloaded, or electrically compromised.
Because the inverter depends heavily on active cooling, any pump malfunction triggers immediate protective logic—reducing hybrid output, disabling EV mode, or shutting the system down.
Quick Reference
- OBD-II Family: P-Code (Hybrid Cooling System)
- Scope: Generic
- System: Inverter / Motor Electronics Cooling
- Difficulty Level: Moderate
- Estimated Repair Cost: €150–€550
- Last Updated: 2025-11-24
Real-World Example / Field Notes
P0A6E appears often on Toyota Prius/Camry/RAV4 hybrids, Lexus CT/RX/ES hybrids, Hyundai Ioniq/Kona hybrids, Kia Niro/EcoDynamics, and GM/Voltec platforms. A Prius we repaired had a coolant pump pulling too much current due to worn internal bearings, causing the ECU to detect a low control signal. A Hyundai Sonata Hybrid showed intermittent P0A6E because of corrosion at the ground terminal, dropping circuit voltage under load. In both cases, inverter temperature spiked during acceleration or hill climbs.
Symptoms of P0A6E
- Hybrid/EV system warning light: Often immediate after startup.
- Reduced power or limp mode: ECU limits inverter heat generation.
- Inverter overheating: Temperature climbs quicker than normal.
- Weak or no coolant circulation: Reservoir shows little movement.
- Overactive cooling fans: Fans may run continuously to compensate.
- Intermittent loss of EV mode: System avoids inverter heat buildup.
- Vehicle shutting down under load (rare): Inverter overheats and disables output.
Common Causes of P0A6E
Most Common Causes
- Short-to-ground in the pump control wire or feedback line.
- Internally failing pump drawing too much current.
- Corroded or loose pump connector reducing voltage.
- Low coolant causing pump cavitation or drag.
- Contamination inside the pump leading to electrical imbalance.
Less Common Causes
- Inverter ECU output driver weakness or partial failure.
- Pump power fuse partially failing under load.
- Grounding issues at chassis, inverter case, or pump bracket.
- Coolant blockage or air pockets increasing pump load.
Diagnosis: Step-by-Step Guide
Your aim is to determine why the ECU sees **low voltage** on the control or feedback circuit—whether due to wiring, pump failure, or a weak inverter driver.
Tools You’ll Need: OBD-II scan tool, multimeter, coolant bleeder/funnel, wiring diagrams, scan tool temperature graphs, basic hand tools.
- Observe inverter coolant temperature. Rising temps at idle indicate poor circulation.
- Command the pump ON using a scan tool. Check if the pump starts, struggles, or runs weakly.
- Check for coolant movement in the reservoir. Minimal turbulence points to low pump output.
- Inspect the pump connector for corrosion or overheating marks. Low voltage often starts at the connector.
- Measure voltage on the control line. If lower than specification, check for shorts or excessive load.
- Perform resistance tests on the pump motor. A failing pump may show abnormal resistance or partial short.
- Check ground integrity. Voltage drop across a bad ground can mimic a “circuit low” fault.
- Inspect wiring harness routing and condition. Look for melted sections near exhaust or power electronics.
- Check coolant level and bleed the system. Air pockets reduce pump efficiency and load the circuit.
- Review freeze-frame data. Useful to see if the fault occurs during idle, charge, or heavy load events.
Pro Tip: If the pump hums loudly, runs hot, or fails intermittently, measure its current draw—high current is a common cause of P0A6E that doesn’t immediately trip fuses but drags the control voltage down.
Possible Fixes & Repair Costs
- Replace the inverter coolant pump: €150–€400.
- Repair shorted or damaged wiring: €40–€180.
- Clean or replace corroded terminals: €10–€60.
- Bleed and refill the inverter coolant system: €40–€120.
- Replace pump fuse, relay, or power module (if faulty): €10–€40.
- Replace inverter driver/output circuit (rare): €300–€550.
Most P0A6E issues come from failing pumps or voltage drops caused by wiring or ground faults. Confirm pump current draw and voltage before replacing high-cost parts.
Can I Still Drive With P0A6E?
It’s not recommended. The inverter and power electronics can overheat quickly if the pump is not operating at full capacity. Driving may trigger limp mode or sudden loss of electric propulsion. If you notice rising inverter temperatures or warnings, stop immediately.
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
- P0A6E indicates a low-voltage condition in the inverter coolant pump control circuit.
- Shorts, internal pump failure, and connector corrosion are the most common causes.
- Driving can quickly overheat the inverter and damage components.
- Check pump current draw and wiring before replacing expensive parts.
FAQ
What causes P0A6E most frequently?
Usually a failing inverter coolant pump drawing excessive current or a short-to-ground in the control wire.
Can I drive with P0A6E?
Not safely. Overheating can occur fast if coolant circulation is weak. Stop driving if warnings appear.
How do I diagnose P0A6E?
Command the pump ON, verify circulation, check voltage on the control line, inspect connectors, and test pump resistance and current draw.
Does P0A6E mean the inverter is failing?
Rarely. The pump or wiring is usually the problem. Inverter driver failure is possible but uncommon.
Can low coolant cause P0A6E?
Yes. Low coolant or trapped air increases pump load and can cause low-voltage faults.