P0515
Universal (All Makes) Vehicle (OBD-II)
Severity: MinorWhat Does This Error Mean?
P0515 means the PCM detected a general malfunction in the battery temperature sensor circuit. This is a broader circuit fault than P0514 (range/performance) — it indicates the sensor circuit is not functioning at all, or has a fundamental electrical problem. Without a functioning battery temperature sensor, the PCM cannot fine-tune charging voltage for temperature. The battery may be over- or under-charged, reducing its lifespan.
Affected Models
- Vehicles 2000 and newer with PCM-controlled charging systems and battery temperature sensors
- Common on GM vehicles with intelligent charging voltage management
- Ford vehicles with Battery Monitoring System (BMS)
- Chrysler, Dodge, Jeep, and Ram vehicles
- European vehicles (BMW, Audi, VW, Mercedes) with sophisticated battery management
Common Causes
- Battery temperature sensor wiring harness has an open or short circuit
- Sensor connector is corroded, loose, or has a backed-out pin causing a circuit fault
- Battery temperature sensor itself has failed completely — open or shorted internally
- Battery was recently replaced and the sensor was not reconnected properly
- Voltage supply or ground reference to the sensor circuit is missing
How to Fix It
-
Locate and inspect the battery temperature sensor connector. Unplug it, check for corrosion or loose terminals, then reconnect firmly. Clear the code and retest — loose connectors are a frequent cause.
Battery area connectors are prone to corrosion from battery off-gassing and moisture.
-
Measure resistance across the sensor terminals with it unplugged. Most sensors are NTC thermistors — at room temperature they typically read 2,000 to 10,000 ohms depending on make. A reading of zero or infinite indicates a failed sensor.
If the sensor reads zero ohms, it has an internal short. If it reads infinite, the internal element is open.
-
Check for voltage at the sensor connector harness side with the ignition on. One wire should supply a 5V reference from the PCM. The other wire is the signal ground return. If either is absent, there is a wiring fault.
Use a wiring diagram to identify which wire is which — the sensor only has two wires and they are not labeled on the connector.
-
Inspect the wiring harness from the sensor connector back toward the PCM or BCM. Look for any melted, chafed, or broken sections. Battery area wiring can be damaged by battery acid drips or improper routing during past battery replacements.
Battery acid contamination looks like white or blue-green crystal deposits on the wiring insulation — it destroys wire insulation over time.
-
Replace the sensor if it fails the resistance test and wiring is intact. After replacement, perform a BMS reset using a scan tool if your vehicle requires it.
On GM vehicles the BMS reset is done through the scan tool's special functions menu. On Ford vehicles it is called the Battery Monitoring System Reset and is similarly performed via scan tool.
When to Call a Professional
The battery temperature sensor is inexpensive and the repair is usually straightforward. If the wiring has a fault, tracing it requires a wiring schematic. BMS reset after repair typically requires a scan tool — a shop can handle this quickly.
Frequently Asked Questions
Why does the PCM care about battery temperature?
Charging voltage needs to be adjusted for temperature. A cold battery (-20°F) needs around 14.8V to charge properly. A hot battery (120°F) only needs about 13.5V to avoid overcharging. Without temperature data, the PCM uses a fixed default charging voltage that is not optimal for either extreme.
Can P0515 cause my car to not start?
Not directly — P0515 itself does not prevent starting. But over time, incorrect charging voltage degrades the battery. A degraded battery eventually causes no-start conditions on cold mornings. Fix P0515 to protect your battery's long-term health.
Is P0515 the same as P0514?
They are related but distinct. P0514 is a range/performance fault — the sensor is working but giving out-of-range readings. P0515 is a circuit fault — the sensor circuit has an electrical problem that is preventing any valid reading. P0515 is generally a more severe electrical fault than P0514.