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P0515 – Battery Temperature Sensor Circuit (OBD2)

P0515 means "Battery Temperature Sensor Circuit". The control unit has detected a fault in the electrical circuit of the charging system: the signal or control current is missing or outside the expected window. The code does not say whether the value is too high or too low, so the wiring and the component itself both have to be checked.

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P0515 quick summary

Fault codeP0515
MeaningBattery Temperature Sensor Circuit
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityHigh
Can I drive?Only briefly. With low charging voltage the battery drains and the engine can stop; with high voltage electronics can be damaged. Have it checked immediately.
Repair cost€0 – €600

How the charging system is monitored

The alternator charges the battery and powers the electrical system while the engine runs; these codes mean the system voltage, the alternator control or the battery temperature sensor is out of range.

A healthy charging system holds the system voltage at about 13.8–14.8 V with the engine running. Many modern cars control the alternator output electronically (smart charging) depending on battery state, temperature and load, using a battery sensor on the negative terminal and an alternator control signal.

Codes P0560–P0563 report that system voltage is faulty, unstable, too low or too high; P0620–P0626 cover the alternator's control, field and lamp circuits; P0514–P0517 the battery temperature sensor.

Low voltage causes starting problems and many random fault codes in other modules; high voltage can damage electronics and boil the battery. Worn alternator brushes and regulators, slipping belts, bad grounds and ageing batteries are the usual causes.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 16899 (P0515). Both numbers mean the same fault.

Symptoms of P0515

  • Battery warning light on
  • Slow cranking or no start
  • Dim or flickering lights
  • Many random fault codes in different modules
  • Battery smell or swelling (overcharging)

Most common causes of P0515 (most likely first)

Mechanic's Pro Tip

After replacing a battery on many modern cars, register it with a scan tool. Otherwise the smart charging system keeps charging it like the old battery, which shortens its life and can bring charging codes back.

  1. 1.Damaged wire or loose, corroded connector at the charging system

    Most likely

    Green or white corrosion, pushed-back pins and chafed insulation near hot or moving parts are the most common findings.

  2. 2.Faulty charging system

    An internal break or short in the component itself.

  3. 3.Blown fuse or missing supply voltage

    If several codes appeared at the same time, check the shared fuse, relay or ground point first.

  4. 4.Worn alternator regulator or brushes

  5. 5.Weak or failed battery

  6. 6.Loose or corroded battery terminals or ground straps

  7. 7.Slipping or worn drive belt

Step-by-step diagnostic guide

  1. 1

    Measure the battery and charging voltage

    Measure the battery voltage with the engine off and with it running at idle and at 2,000 rpm.

    Multimeter: Engine off: about 12.4–12.7 V. Engine running: about 13.8–14.8 V (smart charging systems may vary between about 12.5 and 15 V).

  2. 2

    Check the circuit with a multimeter

    With the ignition off, unplug the charging system and the control unit connector (or back-probe), then check each wire between them for continuity and for shorts to ground and to battery voltage. Compare the component's resistance or supply voltage with the value in the repair manual.

    Multimeter: Wire continuity: below about 1 Ω. Wire to ground with both connectors unplugged: no continuity. Supply/reference with ignition on: usually 5 V for sensors, battery voltage for actuators.

  3. 3

    Load-test the battery

    Test the battery with a proper tester; a weak battery can make a good alternator look bad.

  4. 4

    Check terminals, grounds and belt

    Clean and tighten terminals, check the engine and body ground straps and inspect the drive belt and tensioner.

  5. 5

    Measure voltage drop

    Measure voltage drop on the positive and ground cables while the alternator is loaded.

    Multimeter: Each side should drop less than about 0.3 V under load.

  6. 6

    Check alternator control and battery sensor

    Check the alternator control signal and battery sensor with the scan tool; replace the alternator or regulator if output is wrong.

Frequently asked questions

Can I keep driving with P0515?

Only briefly. With low charging voltage the battery drains and the engine can stop; with high voltage electronics can be damaged. Have it checked immediately.

How much does it cost to fix P0515?

Typical repair costs are 0 € – 600 €, depending on the cause and the vehicle. The most common fixes are: damaged wire or loose, corroded connector at the charging system; faulty charging system; blown fuse or missing supply voltage. Always confirm the cause with the tests above before buying parts.

Can a bad battery cause charging system codes?

Yes. A battery with an internal fault can pull the system voltage down or make it unstable.

How long can I drive with the battery light on?

Only until the battery is empty – often less than an hour. Turn off unnecessary consumers and head to a workshop.

What is the difference between P0515 and similar codes?

P0515 belongs to a group of codes for the same component that differ in the type or location of the fault: P0514 – Battery Temperature Sensor Circuit Range/Performance; P0516 – Battery Temperature Sensor Circuit Low; P0517 – Battery Temperature Sensor Circuit High; P0560 – System Voltage Malfunction; P0561 – System Voltage Unstable; P0562 – System Voltage Low. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.