P2043 indicates that the reductant (DEF) temperature sensor circuit is reporting a value outside the expected range or is behaving irrationally compared to other vehicle temperatures. The control module uses this input to manage DEF heating and dosing strategy. Most often the fault lies with the sensor itself, its wiring, or a connector issue rather than the control module.
The internal sensor element can drift out of calibration or fail outright, producing a voltage or resistance signal that falls outside the range the control module expects for the current operating conditions.
Opens, shorts to ground or voltage, chafed insulation, or harness damage between the DEF tank and control module disrupt the sensor signal and commonly trigger a range or performance fault.
Corroded, backed-out, or moisture-wicked terminals at the sensor or control-module connector introduce high resistance that skews the temperature signal beyond acceptable limits.
Crystallized urea deposits on the sensor probe or severely contaminated fluid can thermally insulate the sensor, causing sluggish or implausible temperature readings that conflict with other vehicle data.
On designs where the temperature sensor is integrated into the DEF tank pump or level assembly, internal faults in the module can set this code even when the external wiring is intact.
A genuinely uncommon internal issue in the control module’s signal processing or analog-to-digital converter can misinterpret a valid sensor input; this should only be considered after physical causes are ruled out.
Short-term driving is usually possible, but prolonged operation can reduce SCR efficiency and may eventually lead to progressive power derates or no-start protections if additional faults accumulate.
Expired or contaminated fluid alone rarely sets a circuit-range code, but crystallized DEF around the sensor probe can insulate it and produce an implausible reading; electrical and sensor faults are far more common root causes.
No—replacing the PCM is usually the wrong fix. The vast majority of P2043 cases are resolved by repairing the sensor, wiring, or connector. Control-module failure is a rare last resort after exhaustive testing.
Serviceability varies by system; some allow individual sensor replacement, while others require replacement of the DEF tank module assembly when the internal temperature sensor fails.