DTC Code P0140 – What does this code mean?

<ul> <li><b>Check Engine Light (CEL) or Malfunction Indicator Lamp (MIL) Illuminated</b>: The primary symptom of DTC P0140 is the illumination of the CEL or MIL. This indicates that the O2 sensor circuit for Bank 1 Sensor 2 is not detecting any activity. <causes> could include a faulty O2 sensor, wiring issues, or a problem with the catalytic converter.</li> <li><b>No Noticeable Drivability Problems</b>: Despite the CEL or MIL being illuminated, there are typically no noticeable drivability issues. This is because the rear O2 sensor (post-catalytic converter) does not affect fuel delivery. It only monitors the efficiency of the catalytic converter. <causes> could include a malfunctioning O2 sensor or issues with the sensor's wiring or connectors.</li> </ul>

<ul><li>Shorted heater circuit in O2 sensor, often necessitating replacement of the heater circuit fuse in the fuse block.</li><li>Shorted signal circuit in the O2 sensor, which can disrupt proper sensor function.</li><li>Melting of the harness connector or wiring due to contact with the exhaust system, leading to circuit interruptions.</li><li>Water intrusion in the harness connector or PCM connector, causing electrical faults.</li><li>Faulty PCM, which can misinterpret or fail to process sensor signals correctly.</li></ul>

<ul> <li><b>Initial Scan</b>: Use an OBD-II scanner to confirm the presence of DTC P0140 and check for any additional codes that may be related.</li> <li><b>Visual Inspection</b>: Inspect the wiring and connectors for the Bank 1 Sensor 2 (B1S2) O2 sensor for any signs of damage, corrosion, or disconnection.</li> <li><b>Check Sensor Voltage</b>: Using a multimeter, measure the voltage at the B1S2 O2 sensor connector. The voltage should fluctuate between 0.1V and 0.9V. A constant voltage indicates a faulty sensor.</li> <li><b>Inspect Exhaust System</b>: Check the exhaust system for any leaks or damage that could affect the O2 sensor readings.</li> <li><b>Test Sensor Heater Circuit</b>: Verify the heater circuit of the O2 sensor by checking the resistance. Compare the readings with the manufacturer’s specifications.</li> <li><b>Check ECM/PCM</b>: Ensure the Engine Control Module (ECM) or Powertrain Control Module (PCM) is functioning correctly and is not the source of the issue.</li> <li><b>Replace O2 Sensor</b>: If all tests indicate the sensor is faulty, replace the B1S2 O2 sensor and clear the code. Re-scan to ensure the issue is resolved.</li></ul>

<p>The DTC code P0140 indicates that the O2 sensor circuit for Bank 1 Sensor 2 is not detecting any activity. This can lead to improper fuel mixture and increased emissions.</p><ul><li><b>Immediate Actions:</b> Inspect the O2 sensor and its wiring for damage or disconnection.</li><li>Check for exhaust leaks that may affect sensor readings.</li><li>Replace the O2 sensor if necessary.</li></ul><p>Delaying repair can result in reduced fuel efficiency and potential damage to the catalytic converter.</p>