The Lambda Sensor (Oxygen Sensor)
1. What is a Lambda Sensor and What is its Purpose?
The lambda sensor, or oxygen sensor, measures the oxygen content in the exhaust gases. This information is sent to the Powertrain Control Module (PCM) to optimize engine parameters:
- Upstream Sensor: Regulates the air/fuel mixture for efficient combustion.
- Downstream Sensor: Monitors the efficiency of the catalytic converter.
2. What are the Symptoms of a Faulty Lambda Sensor?
A faulty lambda sensor can cause:
- Increased fuel consumption.
- Higher pollutant emissions.
- Illumination of the “Check Engine” light (CEL).
- Reduced engine power and responsiveness.
- Irregular engine operation and unstable idle.
3. How to Check if the Lambda Sensor is Faulty?
- If the CEL is on, use a diagnostic tool to read the error codes.
- Functional sensors behave as follows:
- Upstream Sensor: Produces a fast sine wave (0.1V to 0.9V at idle).
- Downstream Sensor: Displays a stable voltage (around 0.45V) if the catalytic converter is in good condition.
- An oscilloscope or scanner can confirm sensor responsiveness.
Always refer to your vehicle’s specific manual for detailed testing procedures.
4. How to Replace a Lambda Sensor?
Here are the general steps to replace a lambda sensor:
- Disconnect the negative battery cable.
- Unplug the sensor’s electrical connector.
- Remove the sensor using a suitable wrench or special socket.
- Install the new sensor in reverse order.
Before proceeding, consult the instructions specific to your vehicle model.