What it means
The motor electronics coolant temperature sensor B reports a circuit high condition. Power electronics cooling cannot be regulated reliably.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
Motor electronics coolant temperature sensor B provides the control module with a temperature signal for the power electronics cooling system. P2BDB sets when the module detects Sensor B’s circuit voltage higher than expected, which may result from a signal wire short to battery power or an open sensor.
Common causes
Most likely first.
- Signal wire shorted to B+
- Open sensor
- Connector pins corroded - high contact resistance
Symptoms
- Hybrid-system warning light or message
- Reduced power
- Power electronics overheating warning
How to diagnose it
- Read freeze-frame data and related codes to see when Sensor B’s high-circuit fault appeared and what temperature value the module received.
- Inspect Sensor B’s connector and harness for corrosion, loose pins, or damage that could expose the signal wire to battery voltage or break the connection.
- Compare Sensor B’s scan-tool reading with other available coolant temperature readings and ambient conditions for an implausible high-circuit value.
- Test the Sensor B signal wire for a short to B+ and check circuit continuity with the manufacturer's wiring diagram and specifications.
- If wiring and connector tests pass, test Sensor B for an open circuit and replace it if it fails the manufacturer's specification.
Common fixes
- Clean and secure corroded or loose Sensor B connector pins.
- Repair the signal wire where it is shorted to B+ or open.
- Replace Sensor B if it is open or fails the specified electrical test.
Can I keep driving?
If a power electronics overheating warning appears or the vehicle limits power, stop safely and avoid driving because cooling control may be unreliable. If no warning is present, keep driving to a minimum and have the Sensor B circuit checked promptly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.