checking o2 sensors with multi meter

[amboldo]

does anyone know how to check a 02 sensor with a multi meter to see if it operational. i'm not sure how to do it, would I use olms ,volts somethind else on the meter? just dont know how to check them. my 97 has two sensors. any help would be greatly appreciated!! Dave A.

[Jim96]

Dave, I don't know if this will help or not. I didn't check mine because my car is a 1990 Geo Metro. I just replaced it. Cost was between $20-30. However this is what the Chiltons manual has to say...

The preferred method for testing this sensor is with the use of an automotive oscilloscope, but any digital multimeter with an internal impedance of 10 megaohms will work just fine. The use of a scan tool that has the ability to monitor the Oxygen sensor's voltge is also helpful. Before the testing can begin , there are a few things that the do it yourselfer should know. Digital Multimeters (DMM) averge the readings that they receive. That simply means that the meter takes the average and displays it. There is usually a bar graph at the bottom of the display screen, this is where the most accurate signal is. This is what all of your findings should be based on. The average is an important reading but means nothing if other factors do not fall into place. Amplitude of the signal needs to be at least 650 millivolts, there should be a switching time from high to low of no more than 100 milivolts or low to high of no more than 125 millivolts, and the number of crosscounts, or the number of times the signal crosses the 450 millivolt mark per second.

1. Bring the vehicle to normal operating temperature.
2. Rev the engine to 2000 rpms and hold the engine speed there.
3. Using a pin, back probe into the Oxygen sensor's signal wire.
4. Attach the device that is to be used for the testing to the pin and a known ground.
5. Be sure to write down all findings for your future reference.
6. Be sure to check for a post catalytic Orgen sensor. These are found on OBD-II compliant vehecles.

Note: The post catalytic Oxygen sensor should not be switching at the same rate as the pre cat. sensor. This sensor is used by the vehicle to monitor the effectiveness of the catalytic converter. If this sensor reaches within 75% of the pre cat sensor, the catalytic converter is bad.

7. Be sure to remove all pins from the sensors. If sensor checks out to be good but problem still present, continue on the next step.

8. In order to perform this next test a scan tool should be used.
9. Disconnect the sensor from the harness.
10. Grab the harness side connector with your fingers.
11. Now with your other hand touch the positive terminal of the batery and look at the scanner. The reading on the scanner should go to the high side of the scale.
12. Now touch the negative terminal of the battery. The reading should go to the low side of the scale.
13. If the readings switch, the PCM side of the circuit is good.
14. Disconnect negative battery cable.
15. Disconnect the electrical connector to the Oxygen sensor.
16. Using suitable tool unscrew the oxygen sensor fro the manifold or pipe.
17. Take care not to damage the tip of the sensor. It is not to come in contract with dirt or fluid and do not attempt to clean the sensor.
18. Installation is reverse of the removal.

Jim

[amboldo]

Thanks very much Jim I'll give it a try!