Faulty reductant temperature sensor, which may be internally open or shorted.; Damaged or corroded wiring harness or connector at the sensor.; Open circuit in the signal or ground circuit between the sensor and the ECM.; Short to voltage on the signal circuit, possibly due to chafed wires.; Failed ECM driver for the sensor circuit, though this is less common.; Contaminated or degraded DEF causing sensor malfunction.; Extreme cold conditions causing the DEF to freeze and the sensor to read abnormally high resistance.

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2045

P2045Reductant Temperature Sensor Circuit High Input

Q: What does code P2045 mean?

Reductant Temperature Sensor Circuit High Input. P2045 indicates that the reductant temperature sensor circuit is reporting a voltage higher than the expected range, which the engine control module interprets as an open circuit or a short to voltage. This sensor monitors the temperature of the diesel exhaust fluid (DEF) to ensure proper operation of the selective catalytic reduction (SCR) system.

P2045 indicates that the reductant temperature sensor circuit is reporting a voltage higher than the expected range, which the engine control module interprets as an open circuit or a short to voltage. This sensor monitors the temperature of the diesel exhaust fluid (DEF) to ensure proper operation of the selective catalytic reduction (SCR) system.

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.
Possible reduction in engine power or limp mode if the SCR system is disabled.
A message on the dashboard indicating low DEF or a fault in the emissions system.
Increased DEF consumption or failure to inject DEF, leading to poor emissions performance.
In some cases, the vehicle may fail an emissions test due to the SCR system being inactive.

Common causes, most likely first

Faulty reductant temperature sensor, which may be internally open or shorted.
Damaged or corroded wiring harness or connector at the sensor.
Open circuit in the signal or ground circuit between the sensor and the ECM.
Short to voltage on the signal circuit, possibly due to chafed wires.
Failed ECM driver for the sensor circuit, though this is less common.
Contaminated or degraded DEF causing sensor malfunction.
Extreme cold conditions causing the DEF to freeze and the sensor to read abnormally high resistance.

How to diagnose and fix it

Use a scan tool to verify the code and check live data for the reductant temperature sensor reading.
Visually inspect the sensor and its connector for damage, corrosion, or loose pins.
Measure the resistance of the sensor with a multimeter and compare to specifications.
Check the wiring harness for continuity and shorts to voltage or ground between the sensor and ECM.
If the sensor is faulty, replace it and clear the code.
If wiring is damaged, repair or replace the affected section of the harness.
After repairs, perform a road test to confirm the code does not return and the SCR system operates correctly.

Reductant Temperature Sensor Circuit High Input

A common oversight is assuming the sensor itself is always at fault, but wiring issues such as a chafed wire shorting to voltage are frequent culprits.
The code can set intermittently due to temperature extremes, so a thorough inspection of the circuit is necessary before replacing parts.
Some vehicles may set this code if the DEF tank is overfilled or contaminated, affecting sensor readings.
The reductant temperature sensor is often integrated into the DEF pump module, making replacement more costly than a standalone sensor.
Always check for related codes in the SCR system, as multiple faults can point to a shared power or ground issue.

Can I keep driving with P2045?

It is generally safe to continue driving with this code, but avoid long trips or heavy loads until repaired, as the SCR system may be disabled, leading to increased emissions and potential limp mode.

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.