P2031 indicates the Engine Control Module (ECM) detected a low voltage condition in the exhaust gas temperature (EGT) sensor circuit for Bank 1 Sensor 2. This sensor monitors post-catalytic converter temperature to verify converter efficiency and protect components from excessive heat. The code means the sensor is reporting an abnormally low temperature value, suggesting an open circuit, wiring fault, or failed sensor.
The exhaust gas temperature sensor itself has failed, typically due to prolonged exposure to extreme heat causing internal sensor degradation or element failure.
The sensor wiring harness has been damaged by heat, chafing, or corrosion, creating an open circuit or short to ground that pulls the signal low.
The sensor connector is corroded, damaged, or has poor pin connections, preventing proper signal transmission to the ECM.
An exhaust leak near the sensor location can allow ambient air to enter, causing false low temperature readings and potentially damaging the sensor.
The sensor tip is contaminated by exhaust deposits, oil, or coolant leaks, affecting its ability to read temperature accurately.
The engine control module has failed or is not properly processing the sensor signal. This is the least common cause and should be diagnosed only after all other possibilities are ruled out.
It is generally not recommended to drive for extended periods. The EGT sensor protects the catalytic converter from overheating. Without accurate temperature monitoring, converter damage or engine damage may occur.
In most cases, only the EGT sensor itself needs replacement. Some sensors come with an integrated connector, while others allow separate harness repair.
No. While the ECM could theoretically fail, it is the least likely cause of P2031. The sensor, wiring, and connectors are the actual culprits in the vast majority of cases. Replacing the ECM is an expensive and usually unnecessary repair.
Yes, most likely. The catalytic converter efficiency is monitored using EGT sensor data. An inoperative sensor will typically trigger a failed emissions test due to the lack of proper catalyst monitoring.