Faulty reductant temperature sensor itself, reading out of range or drifting; Damaged or corroded wiring harness or connector at the sensor; DEF tank heater malfunction causing the sensor to see unrealistic temperatures; Contaminated or crystallized DEF fluid affecting sensor response; Engine control module software calibration issue or internal fault; Poor ground connection shared with the reductant system

DTC codes / P20xx · Fuel and air metering and auxiliary emission controls / P2043

P2043Reductant Temperature Sensor Circuit Range/Performance

Q: What does code P2043 mean?

Reductant Temperature Sensor Circuit Range/Performance. P2043 means the engine control module has detected that the reductant temperature sensor signal is outside its expected range or is not performing rationally compared to other temperature inputs. The computer is not seeing a simple open or short circuit, but rather a signal that is stuck, erratic, or implausible for the current operating conditions.

P2043 means the engine control module has detected that the reductant temperature sensor signal is outside its expected range or is not performing rationally compared to other temperature inputs. The computer is not seeing a simple open or short circuit, but rather a signal that is stuck, erratic, or implausible for the current operating conditions.

SystemPowertrain

Code typeGeneric (all makes)

SeverityMedium

Fix difficultyIntermediate

AreaFuel and air metering and auxiliary emission controls

Symptoms you may notice

Illuminated check engine light, often with no other noticeable symptoms
Reductant system warning message on the dashboard, sometimes limiting vehicle speed or preventing engine start
Poor diesel exhaust fluid (DEF) consumption or dosing strategy that seems abnormal
Rough running or reduced power if the system enters a protective limp mode
In rare cases, a no-start condition after the vehicle sits overnight in cold weather

Common causes, most likely first

Faulty reductant temperature sensor itself, reading out of range or drifting
Damaged or corroded wiring harness or connector at the sensor
DEF tank heater malfunction causing the sensor to see unrealistic temperatures
Contaminated or crystallized DEF fluid affecting sensor response
Engine control module software calibration issue or internal fault
Poor ground connection shared with the reductant system

How to diagnose and fix it

Use a scan tool to read live data from the reductant temperature sensor and compare it to ambient and coolant temperature after a cold soak
Inspect the sensor connector and wiring for corrosion, chafing, or loose pins, and repair as needed
Check the DEF tank heater operation and verify the sensor responds correctly during a commanded heater test
Test the sensor resistance or voltage output against the manufacturer's specification and replace if out of range
Verify DEF fluid quality and concentration, and drain and refill if contaminated
Check for technical service bulletins or software updates for the engine control module
Clear codes and perform a relearn or drive cycle to confirm the repair

When the sensor is not the real culprit

A weak or failing DEF tank heater often sets P2043 before any heater circuit code appears, because the sensor sees a temperature rise that does not match heater command.
Crystallized DEF on the sensor tip can cause a range or performance fault without any visible leak or low-fluid warning.
Some vehicles set P2043 after a battery replacement or low-voltage event because the module loses its learned temperature offset and needs a relearn.
A stuck-open thermostat or a cooling system issue that affects the DEF tank temperature can mimic a sensor fault, so always compare sensor readings to ambient after an overnight soak.
Replacing the sensor without checking the heater circuit or wiring is a common misdiagnosis that leads to a repeat code.

Can I keep driving with P2043?

You can usually drive with P2043 if the vehicle is not in limp mode, but avoid long trips and do not ignore a reductant system warning that limits speed or prevents restart. Have the system diagnosed soon, especially if the weather is cold or the DEF level is low.

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.