P0516 Battery Temperature Sensor Circuit Low

The P0516 OBD-II trouble code means the engine control module (ECM/PCM) has detected that the electrical signal from the Battery Temperature Sensor (BTS) circuit is lower than the expected range.

The important point is that “Circuit Low” refers primarily to the electrical signal, not necessarily to the battery itself being physically too cold.

The battery temperature sensor provides the control module with information about battery temperature so the vehicle can adjust charging strategy appropriately. Depending on the vehicle, this information may be used by the engine control module, body control module, battery management system, or a dedicated charging-system controller.

On many vehicles, the battery temperature sensor is an NTC thermistor. Its resistance changes according to temperature, allowing the control module to calculate battery temperature from the sensor circuit voltage.

What Does the Battery Temperature Sensor Do?

Battery temperature is important because a battery cannot be charged in exactly the same way at every temperature.

A cold battery and a hot battery have different charging requirements.

The charging system may use battery temperature information to adjust:

• Charging voltage

• Alternator output

• Battery charging current

• Battery protection strategy

• Battery state-of-charge calculations

• Start/stop operation

• Energy management

• Electrical load management

For example, charging voltage that may be acceptable for a cold battery could be inappropriate when the battery is already very hot.

The battery temperature sensor therefore helps the vehicle determine how aggressively the battery can be charged.

What Does “Circuit Low” Mean in P0516?

P0516 does not necessarily mean the battery temperature is too low.

It means the control module is seeing a lower-than-expected electrical signal from the battery temperature sensor circuit.

On a typical thermistor-based system, the sensor and an internal pull-up resistor form a voltage divider.

If the sensor circuit is pulled toward ground, the module may see a low voltage and interpret the condition as an abnormally low circuit signal.

Possible causes include:

• Sensor internally shorted

• Signal wire shorted to ground

• Incorrect sensor resistance

• Damaged wiring

• Corroded connector

• Poor terminal connection

• Reference or sensor-supply problem

• Incorrect battery temperature sensor

• Battery sensor integrated into a battery monitoring assembly

The exact interpretation depends on the manufacturer's circuit design.

Common Symptoms of P0516

P0516 may produce very few noticeable symptoms because the engine can often continue operating even when battery temperature information is incorrect.

Possible symptoms include:

• Check Engine Light

• Battery or charging-system warning

• Charging voltage that appears unusual

• Start/stop system disabled

• Increased electrical load management

• Battery charging problems

• Reduced alternator output

• Battery overcharging or undercharging

• Difficulty starting after prolonged electrical use

• Other battery-management or charging-system fault codes

Some vehicles will simply substitute a calculated or default battery temperature when the sensor signal becomes unreliable.

Common Causes of P0516

Faulty battery temperature sensor

The sensor itself may have an internal electrical fault, causing its resistance to fall outside the expected range.

On an NTC sensor, an internal short can produce a very low resistance and consequently a low circuit voltage.

Signal wire shorted to ground

This is an important possibility with a circuit-low code.

A damaged wire may contact the vehicle chassis or another ground circuit, pulling the sensor signal down.

Damaged wiring

Battery areas are exposed to:

• Heat

• Acid or electrolyte contamination

• Moisture

• Vibration

• Corrosion

A damaged harness can therefore create a low signal.

Corroded connector

Battery terminals and nearby connectors can develop corrosion. Even when the connector appears physically intact, corrosion can alter the electrical characteristics of the circuit.

Battery monitoring sensor problem

On some vehicles, the temperature sensor is integrated into a Battery Monitoring System (BMS) sensor or battery-terminal assembly.

In that case, there may not be a separate temperature sensor that can simply be unplugged and replaced.

Incorrect sensor or battery-monitoring component

Installing the wrong component can produce an incorrect resistance-temperature relationship.

Reference/supply problem

Depending on the design, the sensor may use a reference or pull-up circuit supplied by the control module. A problem in this circuit can affect the measured signal.

Control-module fault

An ECM, PCM, BCM or battery-management module problem is possible, but it should generally be considered only after the sensor and wiring have been tested.

How P0516 Should Be Diagnosed

The first step is to determine where the battery temperature sensor is located and which module actually monitors it.

Do not assume every vehicle uses the same architecture.

The sensor may be:

• Mounted directly on the battery

• Attached to the battery terminal

• Integrated into a battery monitoring sensor

• Mounted near the battery

• Integrated into another battery-management assembly

1. Scan all available modules

Do not limit the diagnosis to the engine ECU.

Check the ECM/PCM, BCM and battery-management or charging modules where applicable.

Look for additional codes involving:

• Battery voltage

• Battery current

• State of charge

• Alternator

• Battery monitoring

• Temperature sensors

• Communication networks

A collection of battery-related codes can point toward a common power or communication problem rather than a single defective sensor.

2. Check the freeze-frame data

Record the conditions under which P0516 was stored.

Look at:

• Battery/system voltage

• Engine RPM

• Engine temperature

• Battery temperature reported by the module

• Vehicle operating conditions

• Charging status

If the scan tool reports an extreme battery temperature that does not make physical sense, that is a valuable clue.

Check the Battery Temperature Reading

One of the quickest diagnostic checks is to look at the battery temperature reported by the scan tool.

After the vehicle has been sitting for several hours, the battery temperature should generally be reasonably close to the surrounding temperature.

If the scan tool reports an obviously unrealistic value, such as an extremely low or extremely high temperature while the battery and engine compartment are at normal ambient temperature, the sensor circuit deserves close attention.

This is a plausibility check rather than a universal temperature specification.

Test the Sensor Circuit

For a typical thermistor-based battery temperature sensor, the technician should determine:

• Sensor resistance

• Circuit voltage

• Ground/reference condition where applicable

• Wiring continuity

• Short to ground

• Short to voltage

• Connector condition

The sensor should be tested against the manufacturer's resistance-versus-temperature chart.

There is no universal resistance value that applies to every battery temperature sensor.

For example, two different manufacturers can use different thermistors and different voltage-divider arrangements. Applying a generic resistance value can therefore lead to an incorrect diagnosis.

Why a Short to Ground Is Important

Because P0516 is a circuit-low code, a short to ground is one of the first electrical faults worth investigating.

Suppose the sensor signal normally changes within a particular voltage range.

If the signal wire becomes grounded, the control module may suddenly see a very low voltage.

The module can then interpret this as a sensor circuit low condition.

This means that replacing the sensor without checking the wiring may accomplish nothing.

Check the Connector and Terminals

The connector should be inspected for:

• Corrosion

• Loose terminals

• Bent pins

• Water intrusion

• Battery-acid contamination

• Terminals pushed backward

• Damaged locking tabs

Terminal tension is particularly important.

A connector can look completely normal but fail to maintain a reliable electrical connection.

Battery Condition Should Also Be Checked

Although P0516 is primarily a sensor circuit code, the battery itself should not be ignored.

Check:

• Battery state of charge

• Battery terminals

• Battery condition

• Battery age where relevant

• Ground connections

• Charging voltage

• Battery current if supported

• Battery monitoring sensor operation

A weak or damaged battery does not automatically cause P0516, but charging-system problems and battery-management faults can occur alongside sensor faults.

Can a Cold Battery Cause P0516?

A genuinely cold battery can certainly produce a low temperature reading, but that is different from a low electrical circuit signal.

P0516 is fundamentally an electrical diagnostic code.

If the sensor correctly reports a low physical temperature because the battery is actually cold, the ECM should normally be able to interpret that temperature within its expected range.

The code is generally set when the electrical signal is lower than the module expects, or when the signal is interpreted as being outside the permitted circuit range.

Can P0516 Cause Overcharging?

It can contribute to charging problems depending on the vehicle.

If the charging system relies on battery temperature information and that information is incorrect, the charging strategy may not be appropriate for the actual battery temperature.

The exact response varies considerably between vehicles.

Some systems may use a default temperature value, while others may limit charging or activate a battery-management fault strategy.

Therefore, an abnormal charging voltage should be investigated rather than assuming the alternator is automatically defective.

P0516 and Smart Charging Systems

Modern vehicles increasingly use intelligent charging systems.

The alternator may no longer maintain one fixed charging voltage under all operating conditions.

The vehicle may continuously adjust charging based on:

• Battery state of charge

• Battery temperature

• Electrical demand

• Engine operating conditions

• Regenerative charging strategy

• Fuel-economy requirements

In these vehicles, a battery temperature sensor problem can influence the overall energy-management strategy.

This is another reason why simply measuring alternator voltage at idle and declaring the charging system good or bad may not be sufficient.

What Should Be Repaired?

The correct repair depends on the actual test results.

Possible repairs include:

• Replacing a faulty battery temperature sensor

• Replacing an integrated battery monitoring sensor

• Repairing a signal wire

• Repairing a short to ground

• Repairing damaged wiring

• Cleaning or replacing corroded terminals

• Correcting a sensor ground/reference problem

• Repairing the battery-management circuit

• Addressing a related charging-system problem

• Updating or replacing a control module when manufacturer diagnostics confirm it

The important point is that P0516 should not automatically lead to battery replacement.

The battery can be perfectly healthy while its temperature sensor circuit is faulty.

P0516 vs. Battery Temperature Sensor High/Other Faults

P0516 specifically indicates a low circuit signal.

This is different from a code indicating:

• High sensor input

• Sensor range/performance

• Sensor circuit intermittent

• General sensor circuit malfunction

A low circuit code should make the technician particularly interested in the electrical path pulling the signal downward.

That includes the sensor itself, signal wiring, ground-related problems and the module's input circuit.

Final Diagnostic Summary

P0516 – Battery Temperature Sensor Circuit Low means the control module has detected an abnormally low electrical signal in the battery temperature sensor circuit.

It does not automatically mean that the battery is physically too cold, and it does not automatically mean the battery itself needs to be replaced.

The most important diagnostic checks are:

1. Identify the vehicle's battery-temperature-sensor architecture.

2. Scan all battery-management and charging modules.

3. Check the reported battery temperature with a scan tool.

4. Compare the reading with actual ambient/battery temperature.

5. Inspect the sensor and connector.

6. Test sensor resistance according to the manufacturer's temperature chart.

7. Check the signal voltage.

8. Test for a short to ground.

9. Check wiring continuity and voltage drop.

10. Verify battery, charging-system and battery-monitoring operation.

For P0516, the phrase “Circuit Low” should be treated as an electrical clue first. A low scan-tool temperature reading may be the result of a shorted sensor or signal wire rather than a genuinely cold battery. The sensor, wiring, connector and battery-management architecture should therefore be tested before replacing expensive charging or battery components.