Engine control modules (PCM/ECM/ECUs) rely on oxygen sensors for adjusting engine performance and controlling emission levels. The PCM will display fault code P0140 if the oxygen sensor downstream from the catalytic convert (Sensor 2). This is a weak or non-functioning signal. The row 1 shows the side of the engine where the number 1 cylinder is. The oxygen sensor, also known as the “O2 sensor“, is responsible for reporting to the ECU the amount waste oxygen present in exhaust gases. The ECU uses this information to determine if the fuel ratio being sprayed in the cylinders are too high (rich), or too low.
The oxygen sensor in bank 1, located at sensor 2, is dependent on a reference voltage of 0.45V generated by the engine management module. The O2 sensor will read the oxygen content of the exhaust incorrectly if this voltage is not met or exceeded. This sensor is used to test vehicle emissions. An incorrect signal could cause the vehicle not to pass these tests. This sensor can also cause the engine to run poorly, causing more serious problems with the fuel or exhaust systems.
Table of Contents
What are the causes of fault code P0140?
- Problems with the heater circuit of O2 sensor or fuse (if applicable)
- Oxygen Sensor Cable Breakage, Melting or Loose Connection Issues
- Ingress of water into the connector cable harness
- Sensor for mass airflow (MAF)
- PCM, ECM or ECU Fault
What are the Symptoms of Fault Code P0140?
- Engine fault lights that stay on or flash
- Engine hesitation when accelerating
- Increasing exhaust emission levels
- Smoke from exhaust
- Fuel consumption increases
How to Fix Fault Code P0140?
Check the mass airflow sensor for proper operation and contamination before replacing the O2 sensor. Check the mass airflow sensor to ensure it is working properly and free of contamination before replacing the O2 sensors.
- Repair damaged or loose connectors
- Replace oxygen sensors that are faulty
How Serious is Fault Code P0140?
The fault code P0140 is not a general reason to stop driving the vehicle. The catalytic converter is monitored by the post-catalytic sensor. If the fault is not addressed for a period of time, the catalytic convert may deteriorate or engine components could fail.
