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DTC codes / P0Cxx · Hybrid propulsion / P0C87

P0C87Hybrid/EV Battery Temperature Sensor G/H Correlation

P0C87 indicates that the hybrid or electric vehicle battery pack's temperature sensors G and H are reporting values that do not correlate with each other, meaning the battery energy control module sees a disagreement between two sensors that should track closely. The computer compares their readings under similar conditions and flags the code when the expected relationship falls outside a calibrated tolerance.

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

Symptoms you may notice

  • Illumination of the hybrid system warning light or service vehicle soon message
  • Often no symptoms besides the warning light, especially in mild weather or during short trips
  • Reduced electric-only range or a forced switch to gasoline engine operation in a plug-in hybrid
  • A sudden drop in state of charge or power output when the battery is hot or cold
  • In rare cases, the vehicle may refuse to start or enter a limp-home mode if the disagreement is severe
  • Inconsistent battery cooling fan operation or charging behavior

Common causes, most likely first

  1. A faulty temperature sensor G or H, such as an open circuit, short, or drifted thermistor
  2. Damaged or corroded wiring or connector pins in the sensor harness between the battery pack and the control module
  3. High-voltage battery pack internal bus bar or module connection issues causing localized heating that one sensor picks up
  4. A failing battery energy control module or its internal signal conditioning circuit
  5. Software calibration errors in the battery management system that miscompare sensor readings
  6. Coolant flow problems or blocked air passages that create uneven temperature zones inside the pack
  7. Aftermarket or improper battery repairs that left a sensor unseated or a harness pinched

How to diagnose and fix it

  1. Retrieve all stored codes and freeze-frame data with a scan tool capable of reading hybrid battery sensor values, then record sensor G and H readings at key-on and during a road test.
  2. Visually inspect the battery pack harness, connectors, and sensor mounting points for corrosion, chafing, or loose pins, especially where the harness passes through the pack enclosure.
  3. Measure the resistance of sensors G and H at the sensor connector and compare them to the manufacturer's temperature-resistance chart, checking for opens, shorts, or a drifted value.
  4. Perform a voltage drop test on the sensor signal and ground circuits while wiggling the harness to reveal intermittent faults.
  5. If wiring and sensors test good, check for software updates or recalibration procedures for the battery energy control module before condemning it.
  6. Replace the faulty sensor or repair the harness section, then clear codes and verify that sensor G and H readings track within a few degrees during a charge and discharge cycle.
  7. If the fault persists after sensor and wiring repair, follow the manufacturer's diagnostic flow for the battery energy control module, including power and ground checks, before replacement.

Why sensor correlation codes mislead

  • A correlation code does not automatically mean a sensor has failed; a single hot spot from a weak module connection or blocked cooling passage can make one sensor read high while the other stays normal.
  • Technicians often replace the sensor that reads 'wrong' without comparing both sensors to a known-good reference, such as an infrared thermometer at the pack surface, and the real fault turns out to be a wiring pin that backs out only when hot.
  • Intermittent correlation faults frequently appear only after a long drive or a fast charge, so a cold static test can pass even when the harness has a heat-related open circuit.
  • The battery energy control module may set this code as a companion to other hybrid battery codes, so always check for related temperature or isolation faults before starting repairs.
  • After any battery pack service, sensor G and H must be reseated and the pack sealed correctly; a pinched harness or missing thermal pad can recreate the same correlation fault within a few hundred miles.

Can I keep driving with P0C87?

You can usually drive the vehicle with this code if the warning light is the only symptom, but avoid aggressive acceleration, fast charging, and extreme temperatures until it is diagnosed. If the vehicle enters limp mode or shows a large sudden drop in range, stop and have it inspected promptly.

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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