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Home / DTC / P2045 — Reductant Temperature Sensor A Circuit High

P2045 — Reductant Temperature Sensor A Circuit High

Detailed page for trouble code P2045.

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Code

P2045

Generic P — Powertrain

Reductant Temperature Sensor A Circuit High

Brand: Generic
Type: P — Powertrain
Views: UK: 13 EN: 19 RU: 26
AI status
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Page language: EN

Causes

  • Open circuit in sensor signal or ground wiring (broken wire, disconnected connector)
  • Short to battery voltage on the sensor signal (wiring damaged, chafing)
  • Corroded or contaminated sensor connector
  • Failed reductant temperature sensor (NTC thermistor or integrated sensor)
  • High resistance or poor ground at the sensor or ECM
  • Faulty ECM or internal driver fault (less common)

Symptoms

  • Malfunction Indicator Lamp (MIL) / Check Engine light illuminated
  • Possible reduced engine performance or limp mode depending on manufacturer strategy
  • Reduced or inhibited SCR dosing and/or disabled regeneration events
  • Fault codes related to SCR system or reductant temperature
  • Possible drivability complaints if ECM enters derate

What to check

  • Read freeze-frame and live data with a scan tool; note reductant temperature value and whether it is pegged high
  • Verify other SCR/reductant codes present (heater, level, dosing faults)
  • Perform a careful visual inspection of sensor connector, wiring, and DEF tank/module for damage or corrosion
  • Backprobe sensor signal, reference (usually 5V) and ground with key ON to measure voltage
  • Measure sensor resistance out of circuit (if service manual gives expected values) and compare to temperature chart
  • Check continuity between sensor connector and ECM connector; check for shorts to battery and ground

Signal parameters

  • Typical signal: 0.1–4.9 V depending on sensor design (high code indicates voltage above expected or open circuit)
  • Common thermistor behavior: resistance decreases as temperature rises (for NTC sensors)
  • Typical reference supply to sensor circuit: ~5 V (verify with vehicle-specific manual)
  • Operating temperature range: typically approx. -40°C to +125°C (vehicle-specific)
  • Open-circuit or extremely high voltage reading often triggers 'circuit high' DTC

Diagnostic algorithm

  1. Retrieve all relevant DTCs and freeze-frame data. Confirm P2045 is current and note operating conditions.
  2. Visual inspection: check DEF tank area, sensor, wiring harness, and connectors for damage, corrosion, contamination or loose pins. Repair obvious issues and retest.
  3. With key ON (engine OFF), backprobe the sensor connector and measure: reference voltage, signal voltage, and ground continuity. Compare to expected ranges. A signal near battery voltage or > expected threshold indicates circuit high or open.
  4. Disconnect the sensor and measure connector voltage. If signal remains high with sensor disconnected the problem is upstream (wiring/ECM). If the signal changes, suspect the sensor.
  5. Remove the sensor and measure resistance vs temperature (use room temperature as reference). Compare to service specification or expected thermistor curve. If open/infinite resistance, replace sensor.
  6. Perform continuity checks between sensor ground and chassis/ECM ground and check for shorts to battery voltage on the signal wire. Repair wiring as needed.
  7. If vehicle has a sensor heater, check heater circuit resistance and operation per service manual; verify battery feed and ground to heater.
  8. If wiring and sensor test good, test or substitute known-good ECM connector (or ECU if supported) or consult manufacturer guidance for ECM diagnostics.
  9. After repairs, clear codes, cycle ignition, and confirm live data returns to expected values. Road test and re-scan to ensure code does not return.

Likely causes

  • Disconnected or corroded sensor connector at DEF tank or dosing module
  • Wire harness chafed and touching vehicle power
  • Sensor failed electrically (open circuit or internal short)
  • Heater circuit (if equipped) failed causing abnormal readings
  • Intermittent harness fault or water ingress

Fault status

⚠️ Status
Reductant Temperature Sensor A Circuit High — sensor signal voltage higher than expected or open circuit detected.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P2046 P2047 P20C7
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