P0C85

Code

Generic P — Powertrain

Hybrid/EV Battery Temperature Sensor H Circuit Intermittent/Erratic

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 36 RU: 29

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Poor electrical connection at sensor connector (corrosion, bent pins, loose terminals)
Broken, chafed, or intermittent wiring in the sensor harness
Faulty battery temperature sensor (open, shorted, or intermittent thermistor)
Water intrusion or corrosion at sensor or junctions
Intermittent ground or reference voltage to the sensor
Faulty battery management ECU or intermittent ECU input circuit

Safe work procedures for high-voltage systems first — isolate battery and follow manufacturer HV safety steps before touching pack components
Connect a scan tool and record freeze frame and live data for the affected sensor (sensor H)
Check for additional related codes in the battery thermal management/battery pack group
Visually inspect sensor connector, wiring harness, and junction blocks for damage, corrosion, moisture, or pin damage
Perform a wiggle test of the harness and connector while monitoring live data to reproduce intermittent behaviour
Backprobe connector and verify reference voltage and ground at the ECU (or junction block) with connector connected

Typical sensor is a thermistor (NTC/Pt) — resistance changes with temperature; resistance decreases as temperature rises for NTC types
Sensor output to module typically a variable voltage signal in the 0.1–4.9 V range depending on pack design (verify vehicle-specific values)
Open-circuit condition: very high resistance or voltage at one rail (often near reference voltage)
Short-circuit condition: very low resistance or voltage near 0 V
Intermittent/noisy signal: rapid jumps, spikes, or dropouts when monitoring live data

Use an OBD/scan tool to read codes and freeze-frame data. Note related codes and whether the fault is current or historical.
Observe live temperature sensor H data while performing a key cycle and during vehicle operation. Look for jumps, dropouts, or implausible values compared to other pack sensors.
Visually inspect the sensor H connector, pigtail, and harness routing for chafing, pinch points, corrosion, or water intrusion.
With the vehicle made safe per manufacturer HV isolation procedure, disconnect the sensor and measure its resistance. Compare to expected resistance/temperature curve. Use a heat source (heat gun) or cold spray to verify smooth, monotonic change in resistance.
Reconnect and backprobe the connector (with all safety precautions) to confirm reference voltage and ground present at connector/ECU. Check for intermittent drops while wiggling harness.
If intermittent persists and wiring checks are good, perform continuity and insulation checks on the harness between sensor and battery junction/ECU; repair any damaged wiring or connectors.
Replace the sensor if its resistance/response is out of specification or if evidence of internal failure is found.
After repairs, clear codes and monitor live data under the same conditions that produced the fault. Perform a drive or thermal test to confirm stable readings and no return of the DTC.
If wiring and sensor are good but fault returns, consider ECU/input module diagnostics or replacement per manufacturer guidance.