What is the Principle of Oxygen Sensor Fault Diagnosis?
2 Answers
Oxygen sensor fault diagnosis principle: The PCM (ECM/ECU) monitors oxygen sensor feedback based on the following conditions. 1. Sensitivity: The cycle time of the oxygen sensor from lean to rich and back to lean. When the sensor response time is too long, the PCM detects a fault. 2. Conductivity: If the oxygen sensor voltage remains constant at about 0.3V, the PCM detects an open circuit. When poisoning or aging occurs, the voltage cycle of the oxygen sensor significantly increases or the signal voltage of the oxygen sensor becomes flat. 3. Output voltage: The PCM monitors the output voltage of the oxygen sensor. When the highest and lowest voltages of the oxygen sensor cannot reach the specified values, the PCM detects a fault. If the front heated oxygen sensor fails, the PCM switches the fuel injection system feedback control from closed-loop to open-loop and stores a fault code.
I've worked on many cars, and diagnosing oxygen sensor issues mainly relies on monitoring its signal changes. Simply put, the oxygen sensor located in the exhaust pipe detects oxygen levels and sends feedback to the engine computer to adjust the air-fuel mixture. If it fails, the signal becomes sluggish or stops changing - for instance, the voltage might get stuck at 0.1V or 0.9V. When the engine computer detects this abnormality, it stores a trouble code like P0130 and illuminates the Check Engine light as a warning. In practice, you can easily identify this by reading the codes with a scan tool. I remember my old Ford had this issue once - fuel consumption skyrocketed and the exhaust smelled terrible. Upon inspection, I found the sensor wiring was corroded. If left unrepaired, it not only pollutes the environment but also makes the engine work harder with visible smoke - definitely not cost-effective. My advice? Get it tested at a repair shop immediately before the problem escalates.
