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DTC codes / P0Bxx · Hybrid propulsion / P0BD4

P0BD4Drive Motor Inverter Temperature Sensor C Circuit High

P0BD4 indicates that the drive motor inverter temperature sensor C circuit is reporting an abnormally high signal, which the inverter controller interprets as an overheating condition or a circuit fault. The computer compares the sensor voltage against expected limits and sets this code when the signal exceeds the high threshold for a calibrated time.

SystemPowertrain
Code typeGeneric (all makes)
SeverityMedium
Fix difficultyProfessional
AreaHybrid propulsion

Symptoms you may notice

  • Illumination of the check engine light or service vehicle soon message
  • Reduced power or limp mode due to inverter over-temperature protection
  • Often no symptoms besides the warning light, especially if the fault is intermittent
  • Possible overheating warning message on the dashboard
  • In rare cases, the vehicle may refuse to start or shift into gear

Common causes, most likely first

  1. Faulty inverter temperature sensor C
  2. Damaged or chafed wiring in the sensor circuit (short to voltage or open ground)
  3. Corroded or loose electrical connector at the sensor or inverter
  4. Internal fault in the inverter assembly affecting sensor signal
  5. Coolant flow restriction or low coolant level causing genuine overheating
  6. Failed cooling fan or pump for the inverter cooling circuit

How to diagnose and fix it

  1. Verify coolant level and condition in the inverter cooling system, and check for leaks or blockages
  2. Inspect the sensor connector and wiring for damage, corrosion, or loose pins
  3. Measure sensor resistance and compare to manufacturer specifications (if available)
  4. Backprobe the sensor signal circuit to check for a short to voltage or abnormal high voltage
  5. Check for technical service bulletins (TSBs) or software updates related to the inverter temperature sensor
  6. Replace the inverter temperature sensor C if testing confirms it is faulty
  7. If the sensor is integrated into the inverter, replace the inverter assembly as needed

Don't overlook cooling system faults

  • A genuine overheating condition from a clogged inverter coolant passage can set this code even when the sensor and wiring are perfect.
  • The sensor C circuit may be part of a redundant temperature monitoring system, so a high signal does not always mean the inverter is actually hot.
  • Intermittent high signals often trace to a poor ground connection at the inverter housing rather than a failed sensor.
  • Some vehicles require a relearn or calibration procedure after sensor replacement, which is often missed.
  • A short to voltage in the signal wire can mimic a high temperature reading, so always check for voltage on the signal line with the sensor disconnected.

Can I keep driving with P0BD4?

If the vehicle drives normally and only the warning light is on, you can drive short distances to a repair shop, but avoid heavy acceleration or long trips. If the vehicle enters limp mode or shows overheating warnings, stop driving and have it towed to prevent inverter damage.

Tools that help

Tools we recommend are in the Auto Veteran shop on Amazon. As an Amazon Associate we earn from qualifying purchases.

Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.

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