Error Code P0515 is defined as Battery Temperature Sensor Circuit. That means the BTS is having a problem, usually caused by corrosion or engine overheating. This code is a generic trouble code, meaning it applies to all vehicles equipped with OBD-II system, particularly those made since 1996 up to present. It is common among Chrysler, Dodge, Mazda, Mitsubishi, Jeep, etc., though it applies to all brands. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model to another.

Usually situated near to the battery or mounted inside the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes), the BTS or Battery Temperature Sensor works by converting air temperature surrounding the battery into an electrical signal for the PCM.

The PCM then receives this voltage signal to determine how much voltage the battery will get while charging the battery, based on localized temperature. If the input doesn’t match the normal engine operating conditions, then the Error Code P0515 will be set, even for a second. It also checks the voltage signal from the BTS sensor to determine if it is right at the initial Key On.

Error Code P0515 means there’s a general malfunction detected, and could have been set due to mechanical (damage to the sensor leading to an electrical fault) problem, or electrical (BTS sensor circuit) problem. These problems must not be overlooked in troubleshooting, especially for intermittent conditions.

Normally this code happens when the PCM detects that the BTS circuit has voltage reading outside of the specifications set by the manufacturer; it can be too high or too low.

Common Symptoms

As with other error codes, this code activates the Check Engine light and registers the code to the vehicle’s memory system. Other common symptoms include:

  • Possible low indicated charging voltage
  • Charge indicator light is on

Possible Causes

  • Defective battery temperature sensors
  • Open electrical wiring and connectors
  • Shorted electrical wiring and connectors
  • Battery corrosion
  • Engine overheating

How to Check

As with many error codes, a good starting point to diagnose this code is through the use of TSB (technical service bulletin). Specific manufacturers provide a unique step-by-step guide for diagnosis and repairs of error codes.

Next, find the BTS of the vehicle, this is usually placed near the battery or mounted inside the PCM. Once you find it, check the connector and wiring for any possible damages, such as bare wires, burn spots, rubbing, scraping, melted plastic, etc.

Then, pull the connector apart and inspect the metal parts of the terminals (inside the connector). If you see any signs of burning, or there’s a green tint which indicates corrosion, then that’s a sign of damage. You can use an electrical contact cleaner and a brush with plastic bristle to brush clean the terminals, as necessary. Let it dry, and then apply electrical grease to the terminals in contact.

Next, use the scan tool to scan the diagnostic trouble code present in the vehicle’s memory. Reset and see if the code returns. If the code does NOT return, then that means the problem is simply in the connection. If the code returns, however, then you need to further diagnose the BTS and associated circuits.

With Key Off, disconnect the BTS sensor’s electrical connectors. Then connect a digital voltmeter’s black lead to the ground terminal at BTS sensor wiring harness connector. Then, connect the red label of the voltmeter to the wiring harness connector of the BTS. Turn Key On Engine Off. You must also check the specifications set by the manufacturer; voltmeter must be at 5V. If not, then you must repair the signal or ground wire, or even replace the PCM.

How to Fix

  • Repair or replace damages in the wiring or connector of the BTS
  • Clean connectors and terminals of BTS and its components
  • If the data you get doesn’t match with the specified reference voltage set by the manufacturer, then the BTS must be replaced

If you continue to get the error code after doing all the diagnosis and their corresponding repairs, then that most likely indicates a failed BTS. Failed PCM is highly unlikely, but must not be ruled out too, especially if the code persists after replacing the BTS.

This code may not be a serious problem, but too much corrosion on the battery can lead the battery to fail.