TR
EN
P2044 Reductant Temperature Sensor Circuit Low
P2044 Reductant Temperature Sensor Circuit Low is a generic OBD-II diagnostic trouble code indicating that the Engine Control Module (ECM), Powertrain Control Module (PCM), or aftertreatment control module has detected an electrical signal from the reductant temperature sensor circuit that is lower than the expected range.
In simple terms, the vehicle's computer is receiving a signal that indicates the reductant temperature sensor voltage is too low.
The reductant is usually Diesel Exhaust Fluid (DEF) or AdBlue in modern diesel vehicles equipped with a Selective Catalytic Reduction (SCR) system.
The reductant temperature sensor provides the control module with information about the temperature of the DEF/AdBlue. This information is used to manage:
-
Reductant heating
-
DEF/AdBlue pumping
-
Reductant dosing
-
Freeze protection
-
SCR operation
-
Emissions-system diagnostics
An important point is that P2044 does not necessarily mean the DEF/AdBlue is actually too cold.
A low sensor signal can be caused by an electrical problem such as:
-
Short to ground
-
Low reference voltage
-
Faulty temperature sensor
-
Damaged wiring
-
Corroded connector
-
High-resistance or poor circuit connection
Therefore, the temperature reading and the electrical circuit should be tested before replacing the sensor or DEF tank module.
What Does P2044 Mean?
The code description can be divided into several parts.
Reductant
"Reductant" refers to the fluid used by the SCR system to reduce NOx emissions.
Depending on the vehicle and market, it may be called:
-
Diesel Exhaust Fluid (DEF)
-
AdBlue
-
AUS 32
-
Urea solution
The fluid is injected into the exhaust system and helps the SCR catalyst convert nitrogen oxides into primarily nitrogen and water.
Temperature Sensor
The reductant temperature sensor measures the temperature of the DEF/AdBlue or the temperature inside the reductant tank/module.
The control system uses this information to determine whether the fluid is:
-
Frozen or near freezing
-
Cold
-
At normal operating temperature
-
Excessively warm
-
Outside the expected operating range
DEF can freeze at approximately −11°C (12°F).
Freezing itself is a normal physical characteristic of DEF and does not mean that the reductant system is faulty. The vehicle is designed to account for this condition.
Circuit
The circuit can include:
-
Temperature sensor
-
Signal wire
-
Sensor ground
-
Reference-voltage circuit
-
Electrical connector
-
Wiring harness
-
Reductant tank module
-
Aftertreatment control module
-
ECM/PCM
A fault in any of these components can cause the control module to see a low signal.
Low
"Low" means that the control module has detected a sensor signal below its calibrated threshold.
Depending on the circuit design, a low signal may be caused by:
-
Signal wire shorted to ground
-
Sensor internally shorted
-
Low reference voltage
-
Wiring damage
-
Connector contamination
-
Incorrect sensor resistance
The exact diagnostic interpretation is vehicle-specific.
How Does the Reductant Temperature Sensor Work?
Many reductant temperature sensors use an NTC thermistor, or Negative Temperature Coefficient thermistor.
An NTC thermistor generally behaves like this:
-
Temperature increases → resistance decreases
-
Temperature decreases → resistance increases
The control module uses a reference voltage and the sensor's resistance to calculate temperature.
A simplified sensor circuit can be thought of as a voltage divider.
If the sensor resistance decreases significantly, the sensor signal can fall.
This means a low circuit signal can sometimes correspond to an electrically "hot" condition, but it can also be caused by a short circuit or defective sensor.
The actual sensor design varies between manufacturers, so the specified resistance and voltage values must be obtained from the vehicle's service information.
Why Does the SCR System Need Reductant Temperature Information?
The physical characteristics of DEF/AdBlue change with temperature.
The SCR system needs temperature information to determine how the reductant system should operate.
The temperature signal can influence:
-
DEF/AdBlue heating
-
Pump operation
-
Dosing strategy
-
Freeze protection
-
SCR system operation
-
Diagnostic calculations
If the temperature signal becomes abnormally low, the control module may no longer trust the temperature information and can store P2044.
Symptoms of P2044
Symptoms vary depending on the vehicle and whether the fault is active or stored.
Check Engine Light
The Check Engine Light may illuminate when the control module detects the low reductant temperature sensor signal.
DEF/AdBlue Warning
The vehicle may display messages such as:
-
Check DEF
-
Check AdBlue
-
DEF system fault
-
AdBlue system fault
-
Exhaust fluid system fault
-
SCR system fault
-
Emissions system fault
The exact message depends on the manufacturer.
Incorrect Reductant Temperature Reading
A scan tool may show an implausible temperature.
For example, the displayed temperature may indicate:
-
Extremely high temperature
-
A temperature that does not match ambient conditions
-
A temperature that changes unexpectedly
-
A value near an electrical limit
If the vehicle has been sitting overnight in cold conditions but the reductant temperature suddenly shows an extreme value, the sensor circuit should be investigated.
Reductant Heater Problems
An incorrect temperature signal can affect reductant heater control.
Possible symptoms include:
-
Heater activation at the wrong time
-
Heater not operating correctly
-
Longer DEF warm-up
-
Additional reductant-heater fault codes
SCR System Warning
The vehicle may detect additional problems involving:
-
Reductant dosing
-
Reductant pressure
-
SCR efficiency
-
NOx sensors
-
Reductant heating
Reduced Engine Power
Some diesel vehicles may enter a reduced-power mode if an SCR or emissions fault remains active for an extended period.
Speed Limitation or Countdown
Depending on the manufacturer, persistent SCR faults can eventually lead to:
-
DEF/AdBlue countdown
-
Speed limitation
-
Restart restrictions
-
Other emissions-system operating limitations
No Noticeable Driving Problems
P2044 may initially have little effect on vehicle performance.
The vehicle may drive normally while the ECM stores the code.
This does not mean the problem should be ignored.
Common Causes of P2044
Short to Ground
A short to ground is one of the most important possibilities when diagnosing a low sensor circuit code.
If the signal wire contacts ground, the sensor voltage can be pulled down.
Possible causes include:
-
Chafed wiring
-
Melted insulation
-
Damaged harness
-
Incorrect previous repair
-
Wiring trapped against the chassis
Faulty Reductant Temperature Sensor
The temperature sensor itself may have an internal electrical fault.
Possible failures include:
-
Internal short
-
Resistance too low
-
Incorrect resistance
-
Damaged thermistor
-
Internal connection failure
If the sensor resistance is outside the manufacturer's specifications, replacement may be required.
Damaged Wiring Harness
The reductant system is commonly located underneath or around the vehicle chassis.
Its wiring can be exposed to:
-
Road debris
-
Water
-
Salt
-
Vibration
-
Exhaust heat
-
Abrasion
Damaged wiring can pull the sensor signal low.
Corroded Connector
Corrosion can alter the electrical characteristics of the sensor circuit.
Inspect for:
-
Green corrosion
-
White deposits
-
Rust
-
Moisture
-
Loose terminals
-
Bent pins
-
Damaged seals
Water Intrusion
Moisture inside the connector can create electrical problems.
Water may cause:
-
Short circuits
-
Leakage paths
-
Corrosion
-
Unstable sensor readings
Low Reference Voltage
If the sensor requires a reference voltage and that voltage is too low, the sensor signal can also be too low.
A shared reference circuit problem can affect other sensors connected to the same circuit.
Poor Electrical Connection
A damaged terminal or connector may produce an abnormal signal.
Check:
-
Terminal tension
-
Connector locking
-
Harness splices
-
Ground points
-
Module connectors
Poor Sensor Ground
A sensor ground fault can alter the sensor's signal.
Although ground problems are often associated with unusual or unstable readings, the exact result depends on the circuit design.
Internal Reductant Tank Wiring Fault
On some vehicles, the temperature sensor is located inside the DEF/AdBlue tank module.
The internal wiring connecting the sensor to the external connector can develop an open, short, or poor connection.
Faulty Reductant Tank Module
Some vehicles integrate the temperature sensor into the reductant tank assembly.
If the integrated sensor or internal circuit fails, the tank module may require replacement.
DEF/AdBlue Freezing
DEF freezes at approximately −11°C (12°F).
A frozen fluid condition is not automatically a sensor failure.
However, extremely cold conditions can help reveal an existing sensor or wiring problem.
The temperature sensor should still report a physically plausible cold temperature.
DEF Contamination
Contaminated or incorrect DEF can cause SCR-system problems, but it is not normally the first suspect for a low electrical sensor-circuit code.
If P2044 is present, the electrical circuit should be tested first.
Faulty Control Module
A defective ECM, PCM, or aftertreatment control module input circuit can theoretically cause P2044.
However, the control module should generally be considered only after the sensor, wiring, connector, reference voltage, and ground have been verified.
Software or Calibration Problem
A software or calibration issue can occasionally result in incorrect interpretation of a reductant temperature signal.
Vehicles Commonly Affected by P2044
P2044 can occur on diesel vehicles equipped with SCR and reductant temperature monitoring.
Examples may include:
-
Ford F-250 Super Duty
-
Ford F-350 Super Duty
-
Ford F-450 Super Duty
-
Ford Transit Diesel
-
Chevrolet Silverado Duramax
-
Chevrolet Express Diesel
-
GMC Sierra Duramax
-
GMC Savana Diesel
-
Ram 2500
-
Ram 3500
-
Mercedes-Benz Sprinter
-
Volkswagen Touareg TDI
-
Volkswagen Transporter
-
Audi Q7 TDI
-
BMW X5 Diesel
-
Peugeot Boxer Diesel
-
Citroën Jumper
-
Fiat Ducato Diesel
-
Iveco Daily
-
Renault Master
-
Opel Movano
This list is not exhaustive.
The exact reductant temperature sensor location and construction vary by vehicle. On some models, the sensor is integrated into the DEF/AdBlue tank module.
How Is P2044 Diagnosed?
P2044 should primarily be approached as a low electrical sensor-signal fault.
The objective is to determine whether the low signal is caused by the sensor itself or by an external circuit problem.
Step 1: Scan for Additional Trouble Codes
Use a suitable diagnostic scan tool to retrieve:
-
Stored codes
-
Pending codes
-
Manufacturer-specific codes
-
Freeze-frame data
Look for related codes involving:
-
Reductant temperature
-
Reductant heater
-
DEF/AdBlue level
-
Reductant pressure
-
Reductant pump
-
NOx sensors
-
SCR efficiency
-
Aftertreatment communication
Multiple related codes can indicate a common wiring or module problem.
Step 2: Check Freeze-Frame Data
Review the operating conditions when P2044 was stored.
Useful information includes:
-
Engine RPM
-
Vehicle speed
-
Coolant temperature
-
Ambient temperature
-
Reductant temperature
-
Battery voltage
-
Reductant level
-
Reductant pressure
-
Heater status
This can help determine whether the code occurs primarily during cold starts, warm operation, or another specific condition.
Step 3: Check Live Reductant Temperature
Monitor the reductant temperature PID using a scan tool.
Compare the displayed value with the actual environmental conditions.
If the temperature reading is physically implausible, continue with electrical testing.
Step 4: Inspect the Sensor and Connector
Locate the reductant temperature sensor or tank-module connector.
Inspect:
-
Connector housing
-
Terminals
-
Wiring
-
Seals
-
Sensor body
Look for:
-
Corrosion
-
Moisture
-
Damaged terminals
-
Loose connections
-
DEF crystallization
-
Broken locking tabs
Step 5: Inspect the Wiring Harness
Follow the harness from the reductant tank toward the control module.
Pay particular attention to areas near:
-
Exhaust components
-
Heat shields
-
Chassis brackets
-
Suspension components
-
Harness clips
Look for chafing, melting, pinching, and exposed conductors.
Step 6: Check the Sensor Reference Voltage
Using the manufacturer's wiring diagram, measure the voltage supplied to the sensor.
Verify that the reference voltage is within specification.
If the reference voltage is too low, investigate:
-
Shared sensor circuits
-
Wiring
-
Connectors
-
Control-module output
Step 7: Check Sensor Ground
Verify the sensor ground using the manufacturer's test procedure.
A voltage-drop test can be more useful than a simple continuity check when looking for high-resistance ground connections.
Step 8: Measure the Sensor Signal Voltage
Measure the sensor signal with the circuit connected as specified by the manufacturer.
A low signal can point toward:
-
Short to ground
-
Faulty sensor
-
Low reference voltage
-
Wiring problem
-
Connector problem
Compare the measurement with manufacturer specifications.
Step 9: Check for a Short to Ground
Disconnect the applicable components according to the service procedure and test the signal circuit for an unwanted connection to ground.
A signal wire with an unintended ground connection can pull the voltage down and trigger P2044.
Step 10: Check Sensor Resistance
If the temperature sensor is separately serviceable, measure its resistance.
Compare the result with the manufacturer's resistance-versus-temperature specification.
Possible findings include:
Very low resistance
May indicate an internally shorted sensor.
Resistance outside specification
May indicate a defective sensor.
Resistance changes abnormally
May indicate an internal sensor problem.
Do not use a generic resistance value for all DEF temperature sensors because their characteristics vary by manufacturer.
Step 11: Compare Sensor Temperature With Actual Temperature
Compare the scan-tool temperature reading with the actual reductant temperature or surrounding conditions.
The reading should change logically as the system warms or cools.
A signal suggesting extreme heat when the vehicle has been sitting in cold ambient conditions is a strong reason to investigate the circuit.
Step 12: Perform a Wiggle Test
Monitor the sensor signal while carefully moving the harness and connector.
If the signal changes when the wiring is moved, investigate:
-
Chafed wires
-
Broken conductors
-
Loose terminals
-
Connector problems
-
Internal tank wiring
Step 13: Check the Reductant Heater Circuit
If the vehicle has a reductant heater, check its operation and related fault codes.
A shared power, ground, or harness problem can sometimes affect both systems.
Step 14: Check the Reductant Tank Module
If the temperature sensor is integrated into the DEF/AdBlue tank module, follow the manufacturer's diagnostic procedure for the complete module.
Do not replace the module solely because P2044 is present.
Step 15: Check Control-Module Wiring
Test the wiring between the sensor/tank module and the relevant control module.
Check for:
-
Short to ground
-
Open circuit
-
High resistance
-
Short to battery
-
Poor terminal contact
Step 16: Check the Control Module
If all external components and circuits test correctly, investigate the ECM/PCM or aftertreatment control module.
A faulty input circuit is possible but is generally less common than wiring, connector, or sensor faults.
Step 17: Check Technical Service Bulletins
Check manufacturer technical information for known issues involving:
-
Reductant temperature sensors
-
DEF tank modules
-
Wiring harnesses
-
Connector terminals
-
Software updates
-
Aftertreatment calibration
How to Fix P2044
The correct repair depends on what caused the low sensor signal.
Repair a Shorted or Damaged Wire
If the signal wire is shorted to ground or damaged, repair or replace the affected wiring.
Make sure the harness is:
-
Properly insulated
-
Correctly routed
-
Secured away from heat
-
Protected from abrasion
Repair or Replace the Connector
If the connector has:
-
Corroded terminals
-
Loose pins
-
Damaged seals
-
Broken locking mechanisms
repair or replace the applicable connector components.
Repair the Reference-Voltage Circuit
If the reference voltage is too low because of a wiring or circuit fault, repair the affected circuit.
Repair the Sensor Ground
Repair:
-
Corroded ground connections
-
Broken ground wires
-
Loose terminals
-
High-resistance connections
Replace the Reductant Temperature Sensor
If the sensor fails resistance or signal testing and is separately serviceable, replace it with the correct component.
Replace the Reductant Tank Module
If the temperature sensor is integrated into the DEF/AdBlue tank module and cannot be replaced separately, the applicable tank module may need replacement.
This should only be done after proper electrical testing.
Repair Internal Tank Wiring
If the manufacturer provides a repair procedure for internal tank wiring, repair it according to the specified procedure.
Repair the Reductant Heater Circuit
If testing identifies a shared heater power, ground, or wiring problem, repair the affected circuit.
Repair or Replace the Control Module
If the sensor and wiring are proven good but the control module's sensor input is faulty, the relevant control module may require repair or replacement.
Update Control Module Software
If a manufacturer software update addresses the problem, reprogram the applicable module.
Perform Required Calibration
After replacing a reductant sensor, tank module, or control module, the vehicle may require:
-
DEF system initialization
-
Reductant level reset
-
Temperature-sensor calibration
-
Tank-module programming
-
SCR reset
-
Aftertreatment self-test
The exact procedure depends on the vehicle.
Clear the Code and Verify the Repair
After completing the repair:
-
Clear P2044.
-
Start the vehicle.
-
Monitor reductant temperature.
-
Check sensor signal voltage.
-
Verify reference voltage and ground.
-
Confirm that the temperature reading is physically plausible.
-
Check reductant heater operation if applicable.
-
Test-drive the vehicle.
-
Rescan for stored and pending codes.
The repair should not be considered complete until the reductant temperature signal remains within the expected range and P2044 does not return.
What Happens If P2044 Is Ignored?
If the control module cannot trust the reductant temperature signal, it may not be able to manage the SCR system correctly.
Possible consequences include:
-
DEF/AdBlue warnings
-
Incorrect reductant heating
-
Incorrect dosing strategy
-
Reduced SCR efficiency
-
Increased NOx emissions
-
Additional aftertreatment codes
-
Reduced engine power
-
Speed restrictions
-
Restart restrictions on some vehicles
A vehicle may continue operating normally at first, but persistent SCR faults can eventually result in operating restrictions.
Can You Drive With P2044?
Short-term driving may be possible if the vehicle is operating normally, but P2044 should be diagnosed promptly.
The immediate driving symptoms may be limited to a Check Engine Light or DEF/AdBlue warning.
However, continued operation with an unresolved SCR fault can result in additional warnings or operating restrictions depending on the vehicle.
If the vehicle displays:
-
DEF/AdBlue countdown
-
Reduced-power warning
-
Emissions-system warning
-
Speed limitation
the vehicle should be inspected as soon as possible.
Is P2044 a Serious Code?
P2044 is generally considered a moderate-severity emissions-system fault.
The code specifically indicates that the reductant temperature sensor circuit signal is too low.
The underlying cause could be relatively simple, such as:
-
Shorted signal wire
-
Damaged connector
-
Faulty sensor
However, if the problem remains unresolved, it can affect SCR operation and eventually result in:
-
Increased NOx emissions
-
Reduced emissions-system efficiency
-
Additional fault codes
-
Reduced engine power
-
Operating restrictions
The severity therefore depends on the underlying cause and how long the fault remains active.
P2044 vs. P2045 vs. P2046
These three codes belong to the same reductant temperature sensor circuit family.
| Code | General Meaning |
|---|---|
| P2044 | Reductant Temperature Sensor Circuit Low |
| P2045 | Reductant Temperature Sensor Circuit High |
| P2046 | Reductant Temperature Sensor Circuit Intermittent |
P2044 — Low
The control module detects a sensor signal below the expected range.
Typical possibilities include:
-
Short to ground
-
Low reference voltage
-
Sensor internal short
-
Wiring fault
-
Connector problem
P2045 — High
The control module detects a sensor signal above the expected range.
Typical possibilities include:
-
Open circuit
-
Disconnected sensor
-
Broken signal wire
-
Missing sensor ground
-
High sensor resistance
-
Faulty sensor
P2046 — Intermittent
The sensor signal becomes unstable or temporarily disappears.
Typical possibilities include:
-
Loose connector
-
Broken conductor
-
Chafed wiring
-
Corroded terminal
-
Internal sensor fault
-
Intermittent power or ground
The sequence can therefore be remembered as:
-
P2044 → Low
-
P2045 → High
-
P2046 → Intermittent
P2044 vs. P2047, P2048 and P2049
The next codes move from the reductant temperature sensor to the reductant injection valve circuit.
| Code | General Meaning |
|---|---|
| P2044 | Reductant Temperature Sensor Circuit Low |
| P2047 | Reductant Injection Valve Circuit/Open Bank 1 Unit 1 |
| P2048 | Reductant Injection Valve Circuit Low Bank 1 Unit 1 |
| P2049 | Reductant Injection Valve Circuit High Bank 1 Unit 1 |
The distinction is important.
P2044 concerns the reductant temperature sensor circuit.
P2047 concerns an open reductant injection-valve circuit.
P2048 concerns a low reductant injection-valve circuit.
P2049 concerns a high reductant injection-valve circuit.
Therefore, P2044 does not automatically mean that the DEF/AdBlue injector is defective. The diagnostic focus should initially remain on the reductant temperature sensor, wiring, connector, reference voltage, ground, and tank module.
How to Prevent P2044
Not every electrical failure can be prevented, but regular maintenance can reduce the risk.
Recommended practices include:
-
Inspect DEF/AdBlue wiring during routine servicing.
-
Repair damaged harnesses promptly.
-
Keep reductant-system connectors sealed against moisture.
-
Protect wiring from exhaust heat and abrasion.
-
Inspect harness routing around the DEF tank.
-
Maintain the vehicle's battery and charging system.
-
Use the correct DEF/AdBlue specification.
-
Address DEF and emissions warnings promptly.
-
Avoid unnecessary modifications to aftertreatment wiring.
-
Inspect wiring after exhaust or DEF tank repairs.
-
Follow manufacturer procedures after replacing reductant components.
Final Thoughts
P2044 Reductant Temperature Sensor Circuit Low indicates that the vehicle's control system has detected a reductant temperature sensor signal below the expected electrical range.
The most likely causes include:
-
Short to ground
-
Faulty reductant temperature sensor
-
Damaged wiring
-
Corroded connector
-
Water intrusion
-
Low reference voltage
-
Poor electrical connection
-
Internal reductant tank wiring fault
-
Faulty reductant tank module
-
Control-module problems
-
Software or calibration issues
The most important point is that P2044 does not necessarily mean the DEF/AdBlue itself is too cold.
A low electrical signal can be caused by a sensor that has internally shorted or by a signal wire that is contacting ground. Depending on the sensor design, the control module may also interpret a low signal as an extremely high calculated temperature.
Diagnosis should therefore begin with a scan-tool check of the reductant temperature reading, followed by inspection of the sensor connector and wiring. The reference voltage, sensor ground, signal voltage, sensor resistance, and possible short-to-ground conditions should then be tested against the manufacturer's specifications.
If the sensor is integrated into the DEF/AdBlue tank module, the module should not be replaced simply because P2044 is stored. Replacement should follow testing that confirms the integrated sensor or internal tank circuit is defective.
Ignoring P2044 can eventually result in DEF/AdBlue warnings, incorrect reductant heating or dosing, reduced SCR efficiency, increased NOx emissions, additional aftertreatment fault codes, reduced engine power, and operating restrictions.
The correct repair is to identify the reason for the low sensor signal, repair the wiring or connector or replace the confirmed defective sensor/module, perform any required calibration, clear the code, and verify that the reductant temperature signal remains stable and physically plausible.
