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P0514Battery Temperature Sensor Circuit Range/Performance

The battery temperature sensor is producing a reading that is implausible compared with other temperature data.

Definition

The PCM uses the battery temperature sensor to fine-tune alternator charging voltage — higher voltage for a cold battery, lower for a hot one — and it rationality-checks the sensor against ambient and intake air temperature after a cold soak. P0514 sets when the battery temperature reading is stuck or disagrees with those references beyond a calibrated limit. The PCM then defaults to a fixed charging voltage, which can shorten battery life through chronic over- or undercharging; the MIL or battery lamp may illuminate.

Common causes

  • Faulty or drifted battery temperature sensor
  • Acid corrosion at the sensor connector under the battery tray
  • High-resistance wiring or ground in the sensor circuit
  • Sensor dislodged from the battery tray so it no longer reads battery temperature
  • Skewed IAT or ambient sensor making the comparison fail
  • PCM input fault (rare)

Common misdiagnoses

  • Alternator
  • Battery
  • Voltage regulator
  • PCM

Troubleshooting steps

  1. 1.Compare temperatures after a cold soak

    With the vehicle parked overnight, battery temperature, IAT, and ECT should all read within about 10 degrees F of each other; a battery temperature reading that stands apart is suspect.

  2. 2.Inspect the sensor and tray

    Remove the battery and check the sensor in or under the tray for acid damage, and confirm it is seated in its mounting hole against the battery.

  3. 3.Check connector and wiring

    Look for green corrosion in the connector and measure circuit resistance to the PCM, repairing any connection over 1 ohm.

  4. 4.Test the sensor's response

    Measure sensor resistance and compare it to the temperature chart, or warm it by hand and confirm the scan-tool reading moves smoothly with no dropouts.

  5. 5.Replace and verify charging voltage

    Replace a skewed sensor, then confirm charging voltage varies appropriately with temperature (roughly 13.5-15 V range depending on conditions).

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