Code
P2043
Generic
P — Powertrain
Reductant Temperature Sensor A Circuit Range/Performance
Views:
UK: 21
EN: 53
RU: 38
AI status
Completed
Completed
100%
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
- Connect a scan tool, retrieve fault(s) and live data for reductant temperature A. Note freeze-frame conditions and any related codes.
- Visually inspect the reductant sensor, harness and connector for DEF contamination, corrosion, pin damage or water intrusion. Repair or clean as needed.
- With ignition ON (engine off), backprobe the sensor connector. Verify reference voltage (if applicable), signal voltage and good ground. Compare to expected ranges.
- 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.
- Check continuity between sensor connector and ECU connector pins. Check for shorts to battery and ground using an ohmmeter.
- 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.
- 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.
- 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.
- 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
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