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Home / DTC / P2043 — Reductant Temperature Sensor A Circuit Range/Performance

P2043 — Reductant Temperature Sensor A Circuit Range/Performance

Detailed page for trouble code P2043.

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P2043

Generic P — Powertrain

Reductant Temperature Sensor A Circuit Range/Performance

Brand: Generic
Type: P — Powertrain
Views: UK: 17 EN: 40 RU: 32
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Page language: EN

Causes

  • Failed reductant (DEF/urea) temperature sensor (NTC thermistor)
  • Open or shorted sensor wiring or damaged connector
  • Corroded or contaminated connector (DEF salt/crystals)
  • Short to battery voltage or short to ground in the harness
  • Poor or missing sensor ground/ECU reference
  • Broken sensor heater circuit (if equipped)

Symptoms

  • Malfunction Indicator Lamp (MIL) or fault lamp illuminated
  • Reduced or disabled reductant dosing; possible increased NOx emissions
  • Aftertreatment system warning messages; possible reduced engine power or limp mode
  • Difficulty starting or poor cold-weather reductant behavior
  • Stored freeze-frame or freeze data showing abnormal reductant temperature

What to check

  • Read and record freeze-frame data and live reductant temperature PID with a scan tool
  • Perform a visual inspection of the sensor, wiring harness and connector for damage, corrosion or DEF crystallization
  • Backprobe connector and check for proper reference voltage, signal voltage and ground
  • Measure sensor resistance at known temperatures and compare to specification (or check for smooth change when warmed/cooled)
  • Verify continuity between sensor connector and ECU connector, check for shorts to battery and ground
  • Confirm DEF quality and level; inspect for contamination that may affect sensor

Signal parameters

  • Sensor type: typically an NTC thermistor – resistance decreases as temperature rises (confirm OEM spec)
  • Expected signal: smooth voltage or resistance change corresponding to ambient and warmed reductant temperature
  • Typical signal voltage range: approximately 0.1–4.9 V (varies by design) — verify against vehicle specification
  • Typical resistance reference: many NTC sensors are near ~10 kΩ at 25°C (varies by manufacturer; check spec)
  • Fault conditions: open circuit (very high resistance or no voltage change), short to ground (low voltage), short to battery (near battery voltage), or erratic intermittent values

Diagnostic algorithm

  1. Connect a scan tool, retrieve fault(s) and live data for reductant temperature A. Note freeze-frame conditions and any related codes.
  2. Visually inspect the reductant sensor, harness and connector for DEF contamination, corrosion, pin damage or water intrusion. Repair or clean as needed.
  3. With ignition ON (engine off), backprobe the sensor connector. Verify reference voltage (if applicable), signal voltage and good ground. Compare to expected ranges.
  4. Measure sensor resistance at ambient temperature with connector disconnected. Gently heat the sensor (heat gun or warm water) and observe resistance decrease smoothly; cool and observe increase. Compare to spec.
  5. Check continuity between sensor connector and ECU connector pins. Check for shorts to battery and ground using an ohmmeter.
  6. If sensor has a heater circuit, check heater supply and resistance per service data. Verify heater control by monitoring current or voltage while commanded on.
  7. If wiring and connector are good but signal remains out of range, substitute a known-good sensor or install a new sensor and re-test.
  8. If new sensor reads correctly but code returns and wiring checks are good, inspect ECU grounds and wiring integration; consider ECU input failure or software update as last resort.
  9. Clear codes, perform a drive or system test to verify the system operates correctly and the code does not return.

Likely causes

  • Water/DEF crystal corrosion at connector causing intermittent contact
  • Open wire or pin corrosion between sensor and ECU
  • Sensor failed electrically (out-of-spec resistance or intermittent)
  • Heater element in sensor failed (if sensor includes heater)
  • ECU input damaged or damaged resistor/driver

Fault status

⚠️ Status
Reductant Temperature Sensor A Circuit Range/Performance — signal out of expected range, stuck or not varying properly; check sensor, wiring and ECU inputs.
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 0.5-2.0 hours

Similar codes

P2040 P2041 P2042 P2044 P2045
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