What Does P2042 Mean?
The reductant temperature sensor circuit has detected an electrical fault. This indicates an open circuit, short circuit, or sensor failure preventing proper monitoring of DEF fluid temperature.
Common Causes
35%
Failed reductant temperature sensor
30%
Open or short circuit in sensor wiring harness
20%
Corroded or disconnected sensor connector
10%
Damaged sensor ground circuit
5%
ECM internal fault in temperature sensor circuit
Diagnostic Steps
1
Step 1: Disconnect temperature sensor and measure resistance across sensor terminals
2
Step 2: Compare resistance values to temperature/resistance chart at ambient temperature
3
Step 3: Check continuity of signal and ground wires from sensor to ECM
4
Step 4: Inspect sensor connector for corrosion, moisture, or damaged pins
5
Step 5: Measure reference voltage at ECM connector with sensor disconnected
Estimated Repair Cost
$180 - $500
Parts + labor, varies by vehicle and location
The reductant temperature sensor circuit has detected an electrical fault. This indicates an open circuit, short circuit, or sensor failure preventing proper monitoring of DEF fluid temperature.
The most common cause of P2042 (Reductant Temperature Sensor Circuit) is: Failed reductant temperature sensor
Typical repair costs for P2042 range from $180 to $500, depending on the vehicle, location, and whether you do it yourself or go to a shop.
DEF system may not function properly in extreme temperatures. Vehicle may enter limp mode and could experience starting issues in cold weather if DEF freezing protection is compromised.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P2042 to identify the root cause.
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Quick Info
Category
Powertrain
System
Emissions Control (SCR)
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
