P0A16 – Engine Mount Control Circuit High

P0A16 means the ECU has detected a **range or performance issue** in the Drive Motor “B” inverter temperature sensor — the sensor that measures how hot the rear (or secondary) inverter becomes during operation. A range/performance fault means the temperature signal is present, but it doesn’t behave logically based on real inverter temperature, load, or cooling flow. This can lead to reduced torque, AWD dropout, or EV mode limitations. This guide explains what P0A16 means, the symptoms, causes, diagnosis steps, and the repairs that typically fix this inverter temperature performance problem.

What Does P0A16 Mean?

P0A16 sets when the ECU sees the Drive Motor “B” inverter temperature sensor producing implausible data. Since these sensors are NTC thermistors, the voltage should smoothly decrease as temperature rises. If the signal shifts too slowly, jumps unexpectedly, or does not match expected thermal behavior, the ECU identifies a range/performance fault.

Because inverter overheating can permanently damage power electronics, the system may disable the rear motor, reduce torque, or force cooling measures when this code appears.

Quick Reference

• OBD-II Family: P-Code (Hybrid/EV Powertrain)
• Scope: Generic
• System: Drive Motor “B” Inverter Temperature Monitoring
• Difficulty Level: Moderate
• Estimated Repair Cost: €100–€350
• Last Updated: 2025-11-24

Real-World Example / Field Notes

P0A16 is most common on AWD Toyota/Lexus hybrids (e-AWD), Hyundai/Kia PHEVs, and dual-motor EVs. One Toyota RAV4 Hybrid case showed the rear motor cutting out under light load. Scan data showed inverter temperature rising extremely slowly, then suddenly jumping 20°C — a classic performance issue. The cause was a partially corroded internal sensor terminal reducing the thermistor’s responsiveness. On a Kia Niro PHEV, air trapped in the rear inverter cooling loop caused real temperature lag that the ECU interpreted as a sensor performance fault.

Symptoms of P0A16

• AWD dropout: Rear motor may disable itself during acceleration.
• Reduced EV power: Motor torque is limited for safety.
• Erratic temperature readings: Slow or inconsistent data on the scan tool.
• Cooling fan surges: Fan may run at high speed intermittently.
• Warning messages: “AWD System Malfunction,” “EV System Error,” or “Check Hybrid System.”
• Limp mode: Acceleration or top speed may be limited.
• EV mode dropout: Hybrids may run the engine more often.

Common Causes of P0A16

Most Common Causes

• Degraded or drifting inverter temperature sensor.
• Corroded connector terminals affecting resistance.
• High-resistance wiring causing slow or incorrect sensor response.
• Coolant contamination reducing thermal contact.
• Poor physical contact between the sensor and inverter housing.

Less Common Causes

• Air pockets in the rear inverter coolant loop.
• Low coolant level causing thermal lag.
• Cooling pump performance issues (shared pump systems).
• Inverter genuinely overheating due to blocked cooling channels.
• ECU interpretation failures (rare).

Diagnosis: Step-by-Step Guide

Your goal is to determine whether the sensor is reading incorrectly or the inverter is genuinely heating abnormally.

Tools You’ll Need: EV-capable scan tool, multimeter, wiring diagram, IR thermometer, coolant bleed tools.

1. Monitor live inverter temperature. Look for slow, delayed, or erratic changes.
2. Compare sensor data to inverter load. Temperature should rise steadily under acceleration.
3. Inspect the sensor connector. Look for corrosion, coolant residue, or loose terminals.
4. Perform a wiggle test. Sudden data jumps indicate wiring or connector resistance issues.
5. Test sensor resistance. Measure Ohm values at room temperature and compare to OEM specs.
6. Inspect the wiring harness. Look for heat damage, rodent chewing, or insulation cracking.
7. Check rear cooling loop. Verify coolant level, pump operation, and proper coolant type.
8. Bleed air from the cooling loop. Air pockets can create genuine thermal lag.
9. Use an IR thermometer. Compare true inverter case temperature to scan tool readings.
10. Check for companion codes. Codes like P0A93 or P0A94 help identify real overheating.

Pro Tip: If the inverter case temp rises normally on IR but scan data lags several seconds behind, the sensor or connector has resistance drift — a signature P0A16 pattern.

Possible Fixes & Repair Costs

• Replace inverter temperature sensor: €100–€200.
• Clean or replace corroded connector terminals: €10–€50.
• Repair or replace high-resistance wiring: €10–€100.
• Bleed or flush the rear inverter cooling system: €40–€120.
• Fix coolant leaks causing contamination: €40–€150.
• Replace inverter cooling pump (if weak): €120–€350.

Since P0A16 involves performance rather than complete circuit failure, always check wiring and thermal contact before replacing the sensor.

Can I Still Drive With P0A16?

Driving is usually possible, but the vehicle may disable the rear motor, reduce torque, or enter limp mode. If the inverter is actually overheating, continuing to drive risks major damage. Repair the issue as soon as possible, especially if AWD performance is important.

Last updated: February 13, 2026