P0515 Battery Temperature Sensor Circuit Malfunction

P0515 indicates a malfunction in the battery temperature sensor circuit. The controller cannot trust the temperature input used for charging and thermal compensation.

Code details

Generic OBD-II · P0

System: Speed / Idle
Code type: Generic (SAE / ISO controlled)
Standard: SAE J2012 / ISO 15031-6

Diagnostic boundary

A diagnostic trouble code reports that a monitored test failed. It does not prove one specific part is bad, and manufacturer logic can add vehicle-specific conditions.

Do not replace the alternator for P0515 until the battery temperature sensor circuit has been tested.

Symptoms of P0515

Unstable, high, or low idle, or stalling.
Erratic speedometer, cruise-control, or shift behaviour.
Check-engine light with a hesitation or surge.

Common causes of P0515

A dirty throttle body, idle-control valve, or throttle-position sensor.
A failing vehicle-speed or wheel-speed sensor, or its wiring.
Vacuum leaks or a related sensor forcing the idle/speed strategy.

Useful checks before replacing parts

Check battery temperature sensor data, reference voltage, ground, signal voltage, charging voltage, freeze-frame conditions, and related battery or alternator codes.
Inspect wiring near the battery tray, connector corrosion, acid damage, sensor mounting, grounds, and recent battery or module replacement work.
Compare sensor readings during cold soak and after engine operation to confirm a believable temperature change.

Related OBD-II codes

These nearby speed / idle entries can help compare wording and pin down the fault area.