P2D45

Code

Generic P — Powertrain

Reductant Temperature Too Low

Brand: Generic

Type: P — Powertrain

Views: UK: 21 EN: 30 RU: 21

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Refractant/reductant (DEF/AdBlue) temperature sensor (NTC) failure or short/open
DEF/reductant tank or line heater failure (open circuit, blown fuse, bad relay)
Frozen or partially frozen reductant in tank or lines (ambient temperature below freeze point)
Low reductant level or contaminated/poor-quality DEF affecting flow or sensing
Corroded or damaged connector/wiring (high resistance, intermittent)
ECM/PCM software or control output fault (rare)

Read freeze frame and live data for reductant temperature, ambient temperature, and heater request/status
Verify DEF/reductant tank level and inspect fluid quality for contamination or crystals
Visually inspect sensor and heater connector for corrosion, damage, or water intrusion
Check fuse(s) and relay(s) powering the reductant heater circuit
Backprobe heater supply and ground while commanding heater ON to verify voltage/current
Measure sensor resistance/voltage and compare to expected values at ambient temperature

Reported reductant temperature: typical sensor range -40°C to +120°C (device dependent)
DEF/AdBlue freeze point ≈ -11°C (14°F); readings below this may indicate frozen fluid
Thermistor voltage: typically 0.2–4.8 V depending on temperature and sensor design
Heater element resistance: low-ohm value (typically a few ohms to tens of ohms) — consult vehicle spec
Heater current when commanded: may be several amps; check for expected current draw during heater ON command
Fault condition example: reductant temp reported well below ambient or more than expected delta when heater commanded

Retrieve DTCs and freeze frame with a scan tool; record reductant temperature, ambient temperature, heater command/status and battery voltage.
Visually inspect DEF tank, fill cap, sensor location and harness for damage, corrosion or signs of freezing/crystallization.
Confirm DEF level and quality; if low or contaminated, top up with correct fluid and recheck after warm‑up.
With vehicle cold and then after warm‑up, monitor reductant temperature vs ambient. Command heater ON with scan tool and observe change in temperature and heater status/current.
Check power and ground at heater connector while heater is commanded ON. Verify fuse(s) and relay operation. Repair wiring/connectors as needed.
Measure sensor resistance or voltage at known temperatures (cold ambient and warm fluid). Compare to manufacturer specification; replace sensor if out of range.
If DEF is frozen, thaw system (warm vehicle, ambient heat) and verify heater function; replace heater assembly if it does not maintain or raise temperature.
If wiring and components test OK but issue persists, inspect/replace sensor-heater assembly. If still unresolved, consider ECM/PCM update or replacement after manufacturer guidance.
After repairs, clear codes and perform verification drive or tests to confirm P2D45 does not return.

Heater commanded ON but no current (failed heater element, blown fuse, bad relay)
Sensor output stuck at low temperature (short to ground or open circuit)
DEF frozen due to ambient temperature below freeze point (~-11°C / 12°F)
Poor electrical ground or corroded connector at sensor/heater
Low reductant level preventing sensor from reading fluid temperature