Reductant Temperature Sensor Circuit
P2042 indicates a problem with the reductant temperature sensor circuit in the selective catalytic reduction (SCR) system. This sensor monitors the temperature of the diesel exhaust fluid (DEF) to ensure proper SCR operation and emissions control.
What You Might Notice
- Reduced fuel efficiency
- Excessive black smoke from exhaust
- Diminished engine performance
- Check engine light illuminated
- SCR system malfunction warning
Most Common Causes
- 1
Defective Reductant Temperature Sensor
The sensor may have failed electrically or mechanically, preventing accurate temperature readings to the engine control module. This is the most common cause requiring sensor replacement.
- 2
Corroded or Damaged Wiring
Corrosion, loose connections, or damaged wiring in the sensor circuit can prevent proper signal transmission. Inspect all connectors and harnesses for moisture or deterioration.
- 3
Poor Electrical Connection
Loose, corroded, or improperly seated connectors at the sensor or ECU can cause intermittent signal loss. The connection may appear normal but provide inadequate contact.
- 4
Engine Control Module (ECM) Malfunction
Rarely, a faulty ECM unable to process the sensor signal correctly can trigger this code. This is typically diagnosed after other components have been verified functional.
How to Diagnose It
- 1
Check Defective Reductant Temperature Sensor — The sensor may have failed electrically or mechanically, preventing accurate temperature readings to the engine control module. This is the most common cause requiring sensor replacement.
- 2
Check Corroded or Damaged Wiring — Corrosion, loose connections, or damaged wiring in the sensor circuit can prevent proper signal transmission. Inspect all connectors and harnesses for moisture or deterioration.
- 3
Check Poor Electrical Connection — Loose, corroded, or improperly seated connectors at the sensor or ECU can cause intermittent signal loss. The connection may appear normal but provide inadequate contact.
- 4
Check Engine Control Module (ECM) Malfunction — Rarely, a faulty ECM unable to process the sensor signal correctly can trigger this code. This is typically diagnosed after other components have been verified functional.
How to Fix It
- 1
Replace Reductant Temperature Sensor
Disconnect the sensor connector, remove the old sensor from the DEF tank or line, and install a new OEM reductant temperature sensor. Ensure proper seating and torque specifications are met.
- 2
Inspect and Repair Wiring Harness
Check the entire sensor circuit wiring for corrosion, cracks, or pinches. Clean corroded connectors with electrical contact cleaner, repair any damaged insulation, and replace severely compromised sections.
- 3
Clean and Reseat Electrical Connections
Disconnect the sensor and ECU connectors, clean the terminals with electrical contact cleaner, and firmly reseat them. Apply dielectric grease to prevent future corrosion.
- 4
Check SCR System and Perform Diagnostics
Verify DEF quality and level, inspect the SCR catalyst for damage, and perform comprehensive module diagnostics. If all sensors and connections are verified, the ECM may require replacement or reprogramming.
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