P0C87

Code

Generic P — Powertrain

Hybrid/EV Battery Temperature Sensor G/H Correlation

Brand: Generic

Type: P — Powertrain

Views: UK: 30 EN: 49 RU: 29

AI status

Completed

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Page language: EN

Causes

Faulty temperature sensor G or H (open, shorted, or drifted)
Damaged wiring or poor connector contact between sensors and BMS
Water intrusion or corrosion at sensor connector or inside module
Thermal isolation or physical damage around the sensors causing real temperature gradients
Incorrect sensor installation or wrong replacement sensor type
BMS/module software error, calibration fault, or internal electronics failure

Symptoms

Malfunction Indicator Lamp (MIL) or EV system warning illuminated
Reduced charge/discharge power, limited performance or limp-home mode
Charging limitations (slow charge or refusal to fast charge)
HV battery thermal management system running continuously or unexpectedly
Inconsistent state-of-charge (SOC) or range estimation

What to check

Read stored/active codes and freeze frame data from the BMS and EV control modules
Monitor live data for battery temperature sensors G and H (compare values and response to temperature change)
Visually inspect sensor connectors, harness routing, and battery module entry points for damage or corrosion
Backprobe sensor connectors to measure voltage or resistance with ignition on per manufacturer procedure
Check for water ingress or signs of overheating at the sensor locations and nearby components
Inspect related coolant/thermal management system for proper operation if sensors are coolant-contact type

Signal parameters

Typical sensor voltage range (vehicle dependent): ~0.2–4.8 V at the BMS input
Many battery temp sensors are NTC thermistors — expected resistances vary by design (common: ~1 kΩ–100 kΩ at 25 °C); consult OEM spec
Normal correlation: sensors in the same module/area should track closely — typical expected delta is small (manufacturer-specific; often
Correlation fault triggered when difference or inconsistent rate-of-change between G and H exceeds manufacturer threshold
Signal should change smoothly with temperature; rapid jumps or flatlines indicate wiring/sensor fault

Diagnostic algorithm

Retrieve and record all EV/BMS-related DTCs and freeze frame data. Note temperatures, vehicle state, and ambient conditions.
Monitor live sensor G and H readings with the pack at rest and during a controlled temperature change (ambient warming or apply gentle heat/cold). Confirm both sensors respond and compare offsets.
Visually inspect connectors and wiring for damage, corrosion, loose pins, or water intrusion. Repair or reseal as needed.
With ignition and BMS powered per safety procedures, backprobe the sensor connectors and measure voltage/resistance. Compare to manufacturer values and between G and H.
Perform continuity and short-to-power/ground checks on sensor circuits. Wiggle harness while monitoring to find intermittent faults.
If one sensor appears out-of-spec, swap or substitute with a known-good sensor (if serviceable) to confirm behavior. Do not mix sensor types.
If both sensors read plausibly but disagree, inspect battery module thermal interface and mounting — check for localized heating/cooling that could explain real temperature difference.
Check BMS input circuitry and related fuses/relays. If wiring and sensors test good, consider BMS/software fault; verify calibration or update software per OEM guidance.
Clear codes and perform a drive or charge cycle while monitoring to confirm the fault is repaired and no new related codes set.
Document findings and replace sensor(s), harness, or BMS module only after confirming root cause and following manufacturer repair instructions.

Likely causes

Corroded/loose connector at sensor G or H
Short or open in the sensor harness (intermittent wiring fault)
One sensor failed or out of specification (thermistor drift)
Battery pack thermal imbalance (localized hot/cold spot) causing genuine difference
BMS measurement/input circuit failure

Fault status

⚠️ Status

Battery temperature sensor correlation fault — sensors G and H readings do not match within expected tolerance. Possible sensor, harness, connector, or BMS input issue; further testing required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3 hours