Faulty reductant temperature sensor, which may be internally shorted or have a failed thermistor; Damaged or corroded wiring harness between the sensor and the ECM, causing a short to ground; Loose or corroded electrical connector at the sensor or ECM; Water or DEF intrusion into the connector or sensor, leading to signal corruption; Failed ECM driver circuit for the sensor, though this is less common; Extreme cold temperatures causing the DEF to freeze and the sensor to read abnormally low, though this should not set a code under normal operation

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2044

P2044Reductant Temperature Sensor Circuit Low Input

Q: What does code P2044 mean?

Reductant Temperature Sensor Circuit Low Input. P2044 means the engine control module (ECM) has detected a low voltage signal on the reductant temperature sensor circuit, which monitors the temperature of the diesel exhaust fluid (DEF) tank or lines. The sensor's signal is below the expected range, so the ECM cannot reliably determine the reductant temperature and sets this code.

P2044 means the engine control module (ECM) has detected a low voltage signal on the reductant temperature sensor circuit, which monitors the temperature of the diesel exhaust fluid (DEF) tank or lines. The sensor's signal is below the expected range, so the ECM cannot reliably determine the reductant temperature and sets this code.

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, often with no other noticeable symptoms
A warning message on the dashboard indicating a reductant system fault or low DEF temperature
Possible reduction in engine power or torque as a protective measure
The vehicle may enter limp mode or limit vehicle speed after a certain number of ignition cycles
Difficulty starting the engine in cold weather due to incorrect temperature readings affecting DEF heating

Common causes, most likely first

Faulty reductant temperature sensor, which may be internally shorted or have a failed thermistor
Damaged or corroded wiring harness between the sensor and the ECM, causing a short to ground
Loose or corroded electrical connector at the sensor or ECM
Water or DEF intrusion into the connector or sensor, leading to signal corruption
Failed ECM driver circuit for the sensor, though this is less common
Extreme cold temperatures causing the DEF to freeze and the sensor to read abnormally low, though this should not set a code under normal operation

How to diagnose and fix it

Use a scan tool to verify the code and check live data for the reductant temperature sensor to see if the reading is stuck low or erratic
Visually inspect the sensor and its wiring for obvious damage, corrosion, or contamination, and check connector integrity
Disconnect the sensor and measure its resistance with a multimeter, comparing to the manufacturer's specification for the ambient temperature
Check the sensor signal circuit for a short to ground using a multimeter and wiring diagram, repairing any damaged wires
If the sensor tests out of specification, replace the reductant temperature sensor and clear the code
After repairs, clear the diagnostic trouble codes (DTCs) and perform a road test to confirm the code does not return
If the code persists, follow the manufacturer's diagnostic flow chart for ECM testing or reprogramming

Reductant Temperature Sensor Low Voltage Traps

A common oversight is assuming the sensor itself is at fault, but a short to ground in the wiring harness is frequently the real cause, especially where the harness rubs against the frame or exhaust components.
The reductant temperature sensor is often integrated into the DEF tank or pump assembly, so a low signal can be caused by a failing tank heater or internal wiring, not just the sensor element.
In cold climates, DEF freezing can cause the sensor to read extremely low, but the ECM should recognize this as normal; if the code sets, it indicates a circuit fault rather than just cold temperature.
Technicians sometimes replace the sensor without checking the reference voltage at the ECM connector, which can lead to misdiagnosis if the ECM is not supplying the correct voltage.
This code can be set by a low battery or charging system issue that causes voltage spikes or drops, so always verify battery and charging system health before condemning the sensor.

Can I keep driving with P2044?

You can usually drive the vehicle with this code, but the ECM may limit engine power or vehicle speed after a few ignition cycles, so avoid long trips or heavy loads until it is repaired. Have the fault diagnosed promptly to prevent more severe reductant system issues.

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.