Faulty reductant tank temperature sensor; Damaged or corroded wiring or connector at the sensor; Open or short circuit in the sensor signal or ground circuit; Failed sensor heating element (if equipped) causing implausible temperature readings; Contaminated or degraded diesel exhaust fluid affecting sensor response; Powertrain control module software issue or internal fault (less common)

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P205A

P205AReductant Tank Temperature Sensor A Circuit

Q: What does code P205A mean?

Reductant Tank Temperature Sensor A Circuit. P205A indicates that the powertrain control module has detected an abnormal signal from the reductant tank temperature sensor A circuit, which monitors the temperature of the diesel exhaust fluid tank. The computer compares the sensor voltage to expected values and sets the code when the signal falls outside the normal operating range for a calibrated time.

P205A indicates that the powertrain control module has detected an abnormal signal from the reductant tank temperature sensor A circuit, which monitors the temperature of the diesel exhaust fluid tank. The computer compares the sensor voltage to expected values and sets the code when the signal falls outside the normal operating range for a calibrated time.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illumination of the check engine light or service engine soon light
Often no symptoms besides the warning light
Possible reduced engine power or limp mode in some vehicles
Driver information message indicating diesel exhaust fluid system fault
In rare cases, difficulty starting or rough running if the fluid is frozen or overheated

Common causes, most likely first

Faulty reductant tank temperature sensor
Damaged or corroded wiring or connector at the sensor
Open or short circuit in the sensor signal or ground circuit
Failed sensor heating element (if equipped) causing implausible temperature readings
Contaminated or degraded diesel exhaust fluid affecting sensor response
Powertrain control module software issue or internal fault (less common)

How to diagnose and fix it

Connect a scan tool and record freeze-frame data for P205A, then clear the code and verify if it returns
Visually inspect the sensor, connector, and wiring for damage, corrosion, or loose pins
Measure sensor resistance and compare to manufacturer specifications across known temperatures
Check reference voltage and ground at the sensor connector with a multimeter
Perform a voltage drop test on the signal and ground circuits to rule out high resistance
If wiring and sensor test good, check for technical service bulletins or software updates for the powertrain control module
Replace the reductant tank temperature sensor if faulty, then clear codes and verify repair with a test drive

What Most Techs Overlook on P205A

A failed sensor heating element can cause the temperature signal to stay fixed or read implausibly low, setting P205A without any visible fluid leak or driveability complaint.
Corrosion inside the connector pins is a frequent cause that mimics a failed sensor, so always back-probe the connector under load before condemning the sensor.
The code can be set by a completely separate issue such as a low battery or charging system fault that causes voltage spikes and disrupts the sensor signal.
After replacing the sensor, some vehicles require a relearn or adaptation reset for the reductant system to prevent the code from returning immediately.
Do not assume the tank temperature sensor is the same as the exhaust gas temperature sensor; misidentifying the component leads to unnecessary parts replacement.

Can I keep driving with P205A?

You can generally continue driving with P205A, but avoid long trips or heavy loads until diagnosed, as some vehicles may enter limp mode or refuse to restart after a key cycle if the fault escalates. Do not ignore the code, because a failed temperature sensor can lead to incorrect diesel exhaust fluid dosing and eventual aftertreatment damage.

Tools that help

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Guidance is general and written for all OBD-II vehicles. Exact tests and values vary by model, so confirm the fault before replacing parts.