Reductant Temperature Sensor Circuit Malfunction
The P2042 code indicates a problem with the reductant temperature sensor circuit, which monitors the temperature of diesel exhaust fluid (DEF) in the selective catalytic reduction (SCR) system. The sensor provides critical data to the powertrain control module (PCM) to optimize DEF injection and emissions control. A fault in this circuit can lead to incorrect DEF dosing, increased emissions, and potential derating of engine power.
01. Most Common Causes
- Faulty reductant temperature sensor
- Open or shorted wiring in the sensor circuit
- Corroded or damaged connector
- Failed PCM (rare)
02. Symptoms You Will Notice
- Check Engine Light illuminated
- Reduced engine power or derating
- Increased DEF consumption
- Poor fuel economy
03. Step-by-Step Diagnosis
Step 1: Use a scan tool to retrieve freeze frame data and confirm the code.
Step 2: Visually inspect the sensor and wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor resistance with a multimeter and compare to manufacturer specifications.
Step 4: Check for continuity and shorts in the circuit between the sensor and PCM.
Step 5: If all else is fine, replace the reductant temperature sensor.
04. Commonly Affected Makes
05. Frequently Asked Questions
Is it safe to drive with this code?▼
It is not recommended to drive long distances as the vehicle may enter limp mode, reducing power and potentially causing further emissions system damage.
How much does it cost to fix?▼
The typical repair cost ranges from $50 to $150 for parts and labor, depending on the vehicle and shop rates.