What Does P0A66 Mean?
The hybrid control module has detected a general malfunction in the Phase U current measurement of Drive Motor B (secondary drive motor). The Phase U current sensor or the phase winding itself is producing readings outside acceptable parameters. This disrupts the motor controller's ability to accurately control torque and speed on the secondary drive motor.
Safety Warning
Phase current faults can cause motor overheating and sudden power loss. Tow to a hybrid-qualified repair facility.
Common Causes
35%
Faulty Phase U current sensor within the motor B inverter assembly
25%
Damaged Phase U stator winding in drive motor B
25%
Inverter IGBT degradation on motor B Phase U leg
15%
Phase U cable or connector fault between motor B inverter and motor
Diagnostic Steps
1
Step 1: Monitor all three phase currents for motor B in live data. Identify if Phase U deviates more than 5% from V and W during steady operation.
2
Step 2: With HV system safely de-energized, measure Phase U winding resistance on motor B from terminal to neutral. Compare with V and W — all should match within 0.1 ohms.
3
Step 3: Perform insulation resistance test at 500V on motor B Phase U winding to housing. Below 1 megohm indicates insulation failure.
4
Step 4: Inspect Phase U cable and all connectors for arcing, heat damage, or corrosion.
5
Step 5: If motor and wiring test normal, suspect the motor B inverter Phase U current sensor or power stage — replacement typically required.
Estimated Repair Cost
$500 - $3,000
Parts + labor, varies by vehicle and location
The hybrid control module has detected a general malfunction in the Phase U current measurement of Drive Motor B (secondary drive motor). The Phase U current sensor or the phase winding itself is producing readings outside acceptable parameters. This disrupts the motor controller's ability to accura...
The most common cause of P0A66 (Drive Motor "B" Phase U Current) is: Faulty Phase U current sensor within the motor B inverter assembly
Typical repair costs for P0A66 range from $500 to $3,000, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Phase current faults can cause motor overheating and sudden power loss. Tow to a hybrid-qualified repair facility.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0A66 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid Drive Motor System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
