P2031 Code: Exhaust Gas Temperature Sensor Circuit (Bank 1 Sensor 2)
Is your DPF not regenerating? Code P2031 means the sensor responsible for monitoring your exhaust heat is failing. Here is how to fix it before your filter clogs.
1. What Does P2031 Mean?
The code P2031 stands for "Exhaust Gas Temperature (EGT) Sensor Circuit Bank 1 Sensor 2."
This sensor is critical for diesel engines. It tells the ECU how hot the exhaust gas is before it enters the Diesel Particulate Filter (DPF). If the sensor fails, the ECU cannot safely initiate "Regeneration" (burning off the soot) because it fears melting the filter.
Result: Your DPF clogs up, and the car goes into Limp Mode.
📍 Identifying "Sensor 2"
It is easy to replace the wrong sensor. Here is the layout:
- Sensor 1: Upstream (Before the Catalytic Converter/Turbo).
- Sensor 2 (The Problem): Downstream (Usually located between the Cat and the DPF, or right on the DPF inlet).
Related Codes:
- Voltage Low? Check Code P2032 (Circuit Low).
- Voltage High? Check Code P2033 (Circuit High).
3. Why Did the EGT Sensor Fail?
EGT sensors live in an extreme environment (up to 1200°F). Failures are common due to:
- Thermal Cycling: Constant heating and cooling can crack the internal thermistor or thermocouple.
- Vibration: The sensor is screwed into the exhaust pipe, which vibrates violently, often breaking the internal wires.
- Soot Coating: Heavy soot buildup can insulate the sensor tip, causing it to respond too slowly ("Lazy Sensor").
4. Diagnosis: Resistance Test
Before you spend $150 on a new sensor, verify it is dead. You can do this wirelessly with the iCarsoft CR MAX BT or using a multimeter.
Method A: The Live Data Check (Easiest)
- Connect the CR MAX BT dongle and open Live Data.
- Find EGT Sensor Bank 1 Sensor 2.
- Cold Engine: It should read ambient temperature (e.g., 70°F).
- Start Engine: The temperature should rise smoothly.
- The Fault: If it stays stuck at -40°F (Open Circuit) or spikes to 1800°F (Short Circuit) instantly, the sensor is bad.
Method B: The Multimeter Test
- Unplug the sensor connector.
- Set your multimeter to Ohms (Ω).
- Measure the resistance across the two pins on the sensor side.
- Result: You should see a specific resistance (e.g., 200Ω - 10kΩ depending on temp). If you see "OL" (Open Loop), the internal wire is snapped. Replace the sensor.
Monitor DPF Temps Wirelessly
Watching EGT temps while driving is crucial for diagnosing regeneration issues. The iCarsoft CR MAX BT lets you graph Sensor 1 vs. Sensor 2 data on your tablet.
Shop CR MAX BT6. Frequently Asked Questions
Q: Can I drive with P2031?
A: Not for long. If the ECU can't read the temperature, it will stop DPF regeneration to prevent a fire. This will quickly lead to a clogged DPF, which costs thousands to replace.
Q: I replaced the sensor, but the code came back?
A: Did you inspect the wiring plug? The heat from the exhaust often melts the plastic connector harness side. Also, ensure you tightened the new sensor properly; a loose sensor leaks exhaust and reads incorrectly.
Q: Is there a Bank 2 Sensor 2?
A: Only on dual-exhaust systems (like V8 trucks). If you have that, the code would be P2034.
