P0CB5

Code

Generic P — Powertrain

Hybrid/EV Battery Temperature Sensor O Circuit High

Brand: Generic

Type: P — Powertrain

Views: UK: 20 EN: 35 RU: 24

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Page language: EN

Causes

Open circuit in sensor wiring (broken conductor, disconnected connector)
Corroded or loose connector or pin at sensor or BMS
Failed temperature sensor (open thermistor or internal fault)
Short or leakage to battery pack voltage (pull-up) or another supply
High resistance connection or poor ground in sensor circuit
BMS / control module input fault or internal short

Symptoms

Hybrid/EV system warning or battery system fault lamp illuminated
Battery charge/discharge may be reduced or the vehicle may enter limp/derate mode
HV battery cooling/heating may run continuously or behave abnormally
Loss of expected regenerative braking performance
DTC stored and may reappear after clearing if fault persists

What to check

Read and record freeze frame and all stored DTCs with a capable scan tool
Follow vehicle manufacturer high-voltage (HV) safety procedures before touching HV components
Visually inspect sensor, connector, and wiring for damage, corrosion, or disconnection
Check connector pins for bending, pushed-out terminals, or contamination
Measure sensor circuit voltage at the BMS connector and at the sensor (with appropriate safety and following manufacturer guidance)
Measure sensor resistance with battery service/disconnect per OEM procedure to avoid false readings

Signal parameters

Typical thermistor-type battery temp sensor: resistance varies with temperature (e.g., NTC decreases as temp rises). Expect a finite resistance at ambient (~several kΩ depending on design).
Normal sensor signal voltage range: ~0.1–4.9 V (varies by design). 'High' fault usually means voltage near supply rail or open circuit (e.g., >4.5–4.8 V).
Open-circuit indication: very high resistance or infinite (open) when measured with pack/service disconnect in place as required by OEM procedure
Short-to-rail indication: voltage near pack or reference supply instead of expected sensor voltage

Diagnostic algorithm

Verify DTC: Connect a professional scan tool, confirm P0CB5 and note freeze-frame data and occurrence conditions.
Safety: Follow OEM HV isolation/disable procedure before performing any resistance or continuity tests on the HV battery harness or sensors.
Visual inspection: Inspect sensor O connector, wiring route, harness chafe points, and BMS connector for damage/corrosion. Repair obvious damage.
Check connector continuity/pins: With HV system made safe per OEM, disconnect connectors and check for bent pins, corrosion, and proper seating.
Measure resistance at sensor: Remove sensor connector and measure the thermistor resistance (or as specified). Compare to expected OEM values for ambient temperature. An open/infinite reading supports an open sensor circuit.
Measure signal voltage at BMS: With ignition/vehicle in the required state (follow OEM instructions) measure the sensor signal voltage at the BMS harness. A voltage near the supply rail indicates an open/high condition.
Check harness continuity: Measure continuity between sensor pin and BMS input pin; repair any open or high-resistance segments. Inspect for shorts to supply or ground.
Check reference/pull-up: Verify the BMS reference/pull-up (often to 5 V or internal pull-up) is present and not incorrectly high due to module fault.
Repair/replace: Replace damaged wiring, corrosion-affected connectors, or the temperature sensor if it tests open or out-of-spec. Use OEM-specified parts and torque/seal practices.
Clear DTCs and test: Re-enable HV system per OEM, clear codes, then run functional test/road test and monitor battery temperature sensor readings and BMS behavior to confirm the fault is resolved.
If fault returns: Suspect BMS module input fault; perform advanced module diagnostics or contact OEM technical support and follow their guidance before replacing high-cost modules.