My car drives perfectly. Is this code actually worth fixing?

It is worth fixing, but there is no rush and no risk in driving meanwhile. The damage P0515 causes is slow: an uncompensated charging voltage shortens battery life, most noticeably in climates with hot summers or hard winters. Think of it as a maintenance item with a deadline measured in months rather than an urgent repair. The one reason to move faster is that the fix is frequently a corroded connector under the battery, and corrosion under a battery does not stay put — it spreads to the cables and terminals, which is a much more annoying problem.

The code appeared right after I put a new battery in. Coincidence?

Very unlikely. The two things that go wrong during a battery swap are both easy to do and easy to fix. Either the sensor was never reconnected and is sitting loose in the engine bay, or its wire got pinched between the new battery and the tray as the hold-down was tightened. Lift the battery back out, find the pigtail, and check both. It costs nothing to look and resolves a large share of P0515 cases that follow a battery replacement.

Where is the battery temperature sensor?

There are three common answers and you need to know which applies to your vehicle. Many Chrysler, Dodge and Jeep models put a small thermistor in or under the battery tray, sensing the battery case from below. Several Toyota and Lexus applications place it inside the battery box itself. Newer vehicles increasingly have no separate sensor and instead use a combined battery sensor clamped onto the negative terminal that measures temperature, voltage and current together. Check service data for your year and model before you start hunting.

How is P0515 different from P0516 and P0517?

All three concern the same input, but the directional codes tell you which way the signal failed and, usefully, what the module did about it. P0516 means the signal is stuck low, which a negative-coefficient thermistor circuit reads as very hot, so the module lowers charging voltage and the battery is chronically undercharged. P0517 means stuck high, read as very cold, so voltage is raised and the risk becomes overcharging. P0515 is stored when the module rejects the input without a clean directional signature, so the diagnosis is the same but the consequence is the neutral fallback rather than an error in one direction.

OBD-II trouble code

P0515: Battery Temperature Sensor Circuit

The module has lost a credible battery temperature reading, so it can no longer tune charging voltage to how warm or cold the battery actually is — a code about battery lifespan, not about how the car drives.

Low severityPowertrainCharging / ElectricalDrivable short-term

Quick facts

System: Powertrain
Category: Charging / Electrical
Severity: Low severity
Drivable: Usually safe to drive short-term
Repair cost range: $70 – $400
DIY difficulty: Beginner DIY

What does P0515 mean?

Almost every code in a diagnostic library describes something that affects how an engine runs. P0515 does not, and understanding why is the whole point of the page. A lead-acid battery does not accept charge the same way at every temperature. Cold, its internal resistance rises and it needs a higher voltage to take charge at all. Hot, the opposite is true — the same voltage that was correct at freezing will drive a warm battery into gassing, boiling off electrolyte and shortening its life considerably. Manufacturers solved this by measuring battery temperature and sliding the target charging voltage up or down accordingly.

P0515 is the general circuit code for the sensor that makes that possible. The module has decided the input is not usable and cannot classify it cleanly as stuck low or stuck high, so it stores the undirected member of the family. What happens next is a fallback: the charging system reverts to a fixed default voltage, typically somewhere around 13.8 to 14.2 volts. That default is a compromise chosen to be survivable in most conditions, not correct in any of them. The car keeps running, the alternator keeps charging, and the only thing quietly suffering is the battery.

Where the sensor lives varies enough to matter for both diagnosis and cost. Chrysler, Dodge and Jeep applications — where this code appears most often — traditionally mount a small thermistor in or under the battery tray, sensing the case from below, with a two-wire pigtail running to the engine harness. Some Toyota and Lexus applications place it inside the battery box. A growing number of newer vehicles have no separate sensor at all: the function is folded into an intelligent battery sensor clamped to the negative terminal, which measures temperature, voltage and current together and reports over a data line. That last case changes the repair completely, because the part is neither cheap nor a simple two-wire swap.

One consequence is worth flagging in advance. On vehicles that use a temperature-compensated charging strategy, some also require the battery to be registered or the charging system to be reset after a battery is replaced. If P0515 appeared shortly after a battery change, look first at whether the sensor was reinstalled at all — it is easy to leave one dangling in the engine bay or pinched under the new battery, and both produce this code without any part having failed.

Common causes

Failed battery temperature sensor (open or drifted thermistor)
Sensor left disconnected, dangling or pinched after a battery replacement
Corroded connector or pigtail, attacked by electrolyte seepage from the battery directly above it
Chafed or broken wiring between the sensor and the engine harness, often where it exits the battery tray
Poor ground for the sensor circuit at the module or at a body ground point
Intelligent battery sensor at the negative terminal failing or losing communication, on vehicles that integrate the function
Aftermarket battery tray or hold-down installed without transferring the original sensor
Powertrain module fault affecting the sensor input, which is uncommon and should be the last conclusion

Symptoms

Check engine light on with P0515 stored and no change in how the engine runs
Battery temperature shown in live data as absent, frozen, or an obviously impossible value
Charging voltage that stays at one fixed figure regardless of weather or how long the engine has run
Batteries that need replacing noticeably more often than they should
Slow cranking in cold weather because a cold battery was never given the higher voltage it needed
Battery case warm or the engine bay smelling faintly of sulphur after long summer drives
Occasionally, a charging system warning lamp on vehicles that treat this input as critical

Diagnostic steps

1.Find the sensor before anything else. Check service data for your specific application — under the battery tray, inside the battery box, or integrated into the terminal-clamp battery sensor. The three cases have almost nothing in common diagnostically.
2.Look at battery temperature in live data with the engine cold after an overnight soak. It should read close to outside air temperature. A value pinned at a limit, or one that reads nothing at all, confirms the circuit rather than the strategy is at fault.
3.Lift the battery out and inspect underneath. This sensor sits directly below a lead-acid battery, so acid seepage, white crystalline corrosion and a green-tinged pigtail are common findings and are frequently the entire fault.
4.Measure the sensor's resistance and compare it against the manufacturer's temperature-resistance table at a known temperature. These are ordinary negative-coefficient thermistors, so resistance should fall as it warms — warming it gently in your hand should move the number.
5.Back-probe the two wires at the harness connector with the key on. You are looking for a reference voltage on one and a solid ground on the other; a missing ground explains the code with a perfectly good sensor still fitted.
6.Measure actual charging voltage at the battery posts at idle, then after twenty minutes of running. If it is fixed at one value and never compensates, you are seeing the fallback strategy in action, which confirms the module has genuinely given up on the input.

Repair cost

$70 – $400

A conventional two-wire battery temperature sensor is an inexpensive part, typically $15-$60, and the labour is mostly the time to lift the battery out — expect $70-$180 all in. Repairing a corroded connector or pigtail runs $90-$220 and is the most common actual fix. Where the function lives in an intelligent battery sensor on the negative terminal, the part alone is usually $70-$220 and some applications require the new sensor to be configured with a scan tool, putting the job at $180-$400. Diagnosis alone is $80-$150.

Estimate your repair

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Open the Repair Cost Estimator with battery temperature sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.

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DIY vs shop

This is a beginner-friendly repair. Common hand tools, a free afternoon, and a willingness to follow a procedure are usually enough. The risk of causing a bigger problem is low if you read up on your specific vehicle first.