What Does P0A31 Mean?
The Drive Motor 'B' Temperature Sensor Circuit Range/Performance code indicates that the Motor B temperature sensor is electrically functional but its readings do not match expected values based on motor operating conditions. The Motor B controller cross-references temperature data against motor current, speed, ambient temperature, and coolant temperature to validate the sensor. This fault suggests the sensor has drifted from its calibration, has poor thermal coupling, or there is a cooling system anomaly creating unexpected temperature gradients.
Common Causes
30%
Temperature sensor degradation with shifted thermistor resistance curve
25%
Poor thermal contact between the sensor and Motor B housing surface
20%
High-resistance wiring connection attenuating the sensor signal
15%
Motor B cooling system restriction causing localized temperature variation
10%
Controller calibration discrepancy following a software update
Diagnostic Steps
1
Compare the Motor B temperature sensor scan tool reading with an infrared thermometer measurement on the motor housing; a difference greater than 15 degrees confirms a sensor or mounting issue.
2
Verify the sensor is properly seated in its mounting bore with correct torque and thermal compound (if specified); a sensor that has backed out will read lower than actual motor temperature.
3
Check the Motor B cooling system for proper coolant flow, level, and condition; partial blockages can create temperature gradients that trigger range/performance faults.
4
Measure the sensor circuit wiring resistance from end to end and compare to specification; even 5-10 ohms of added resistance in a thermistor circuit can significantly shift readings.
5
Replace the Motor B temperature sensor if mounting and wiring are confirmed good; perform any manufacturer-required sensor calibration or learn procedure after replacement.
Estimated Repair Cost
$200 - $800
Parts + labor, varies by vehicle and location
The Drive Motor 'B' Temperature Sensor Circuit Range/Performance code indicates that the Motor B temperature sensor is electrically functional but its readings do not match expected values based on motor operating conditions. The Motor B controller cross-references temperature data against motor cur...
The most common cause of P0A31 (Drive Motor "B" Temperature Sensor Circuit Range/Performance) is: Temperature sensor degradation with shifted thermistor resistance curve
Typical repair costs for P0A31 range from $200 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Inaccurate Motor B temperature readings may result in premature thermal derating or failure to protect the motor from actual overheating. Monitor for signs of reduced rear motor performance.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0A31 to identify the root cause.
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Quick Info
Category
Powertrain
System
Hybrid/EV Powertrain
Difficulty
Type
Generic (SAE)
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