Lambda sensors, unlike other types of sensor fitted to an engine, have an optimum performance life cycle, which generally lasts about 45 000 to 60 000 thousand miles. The decrease in performance happens gradually to a point where the sensor will become tired or lazy. The sensor still works but the reaction times are slow. Regular drivers of the vehicle will not notice this change. Testing a Zirconia Lambda sensor off the vehicle is quite easy, all you need is a vice or a similar means of holding the sensor, a propane torch and a high impedance digital multimeter.
First check the general condition of the sensor if there is any sign of damage change the sensor. Now test the heater circuit for continuity, if the heater has failed change the sensor. now connect the voltmeter red probe to the signal wire (generally black) and the black probe to the earth (generally grey) and set voltmeter to .000 volts. Then with a propane torch heat up the tip of the sensor until it is cherry red. The sensor should give off a reading of nearly 1 volt in a few seconds. If it takes longer than 20 seconds to get a reasonable reading change the sensor. In the case of a 1 or 3 wire sensor the body of the sensor is the earth. (For wire colours see chart).
One of the most misdiagnosed reasons for changing a Lambda sensor is when the vehicle fails an MOT on the emission test when the Lambda reading is high. This is not a measurement of the Lambda sensor but a calculation of the burn. High Lambda in this case is too much oxygen in the exhaust system; usually a pinhole in the exhaust after the Lambda sensor. Check if the exhaust is in good condition or has had any part replaced recently, and this will be the most likelly cause, not the Lambda sensor.
Hi,
During the process of changing/looking at new O2 sensors I found this - might help someone else so...
I have not tried this yet - but according to Lucas - should work for all Zirconia sensors.
The document is here:
http://www.lucaselectrical.co.uk/catalogues/LucasLamdaXCB462_Full.pdf
Here is a précis of the test..
Lambda sensors, unlike other types of sensor fitted to an engine, have an optimum performance life cycle, which generally lasts about 45 000 to 60 000 thousand miles. The decrease in performance happens gradually to a point where the sensor will become tired or lazy. The sensor still works but the reaction times are slow. Regular drivers of the vehicle will not notice this change. Testing a Zirconia Lambda sensor off the vehicle is quite easy, all you need is a vice or a similar means of holding the sensor, a propane torch and a high impedance digital multimeter.
First check the general condition of the sensor if there is any sign of damage change the sensor. Now test the heater circuit for continuity, if the heater has failed change the sensor. now connect the voltmeter red probe to the signal wire (generally black) and the black probe to the earth (generally grey) and set voltmeter to .000 volts. Then with a propane torch heat up the tip of the sensor until it is cherry red. The sensor should give off a reading of nearly 1 volt in a few seconds. If it takes longer than 20 seconds to get a reasonable reading change the sensor. In the case of a 1 or 3 wire sensor the body of the sensor is the earth. (For wire colours see chart).
One of the most misdiagnosed reasons for changing a Lambda sensor is when the vehicle fails an MOT on the emission test when the Lambda reading is high. This is not a measurement of the Lambda sensor but a calculation of the burn. High Lambda in this case is too much oxygen in the exhaust system; usually a pinhole in the exhaust after the Lambda sensor. Check if the exhaust is in good condition or has had any part replaced recently, and this will be the most likelly cause, not the Lambda sensor.