Oxygen sensor tests ( Stock Narrow band type):         

Off vehicle.
Remove front oxygen sensor, Oxy, 0   or Lambda or B1S1. (bank 1 Sensor 1 or bank 2 Sensor1.)
To test any sensor off car, you need to know what brand of sensor  and part number, to know what wire colors it uses.
If it's still the stock sensor, hit the home button above and see the colors of all wires. Stock car. (Stock means , as car left the Factory , lock box stock)
This test only finds CATASTROPHIC sensor failures and never biased, offset or poisoned sensors, (commonly caused by putting crap fuel additives in the tank, just don't)

Testing O2 sensors on the workbench.

Tools , any  DMM  volt  meter and a propane torch.
Use a high impedence DC voltmeter   (any  meter, but  not analog needle meters, as some old ones, are very low impedance)


First test  the heater wire (if present) using the meters resistance ohms scale,  if low ohms it's good, if infinity or over about 50 ohms its bad. If bad , end all testing.
Spec. heater ohms is 12. (FSM) (I = E/R so I  (current) is near 1 amp on car,  a tad more running)
I apply 12vdc to the heater wires, and my camp on, ammeter reads about 1amp,  and the sensor gets real hot. do not touch it now. Never touch it with the heater on.

Clamp the sensor in a vice, or use  vice-grip to hold it, it to something burn poof.  ( use a VISE)
Clamp your negative voltmeter lead to the case, and the positive to the Sensor CELL + output wire.  If 4 wire sensor connect the meter minus to CELL minus wire)
Set the meter to 2vdc range or let it autorange on DC volts.
The volts now  is 0v.  (power up the heater now,  if the voltage jumps to over 1v, the sensor has a short from heater to CELL)
Power off the heater, let it cool.  (  I want to test only the CELL now, using external heat.)
Use a propane torch set to high and the inner blue flame tip to heat the fluted or perforated area of the sensor.
The torch gets it hot (wakes it up)  but you can play with the flame once hot, to block oxygen path to the sensor,,takes practice on a new sensor.
The torch flame can be very low in oxygen, that blue flame is a clue to perfect combustion.
So if you jog the flame to one side fast ,oxy rich  air hits it and you get up to 1v. out. (practice this)

You should see a DC voltage rise of at least 0.6 within 20 seconds.  or even as high as 0.9v.
If not, most likely cause  is open circuit internally  or fouled   It's bad, who cares why? (sure stop using nasty additives in your fuel, use Chevron Techron, it's the only safe brand (no axe to grind)
Or just burn Chevron fuel  and never ever use additives.  (snake oil is just that)
If OK so far, remove from flame. You should see a VOLTAGE drop to under 0.1 volt within 4 seconds.
If not, then it is  likely silicone fouled. (yah , wrong engine sealants or again,  snake oil killed) 
I saw one set of  02 that had a purple tips, and was from snake oil. (no idea who's)  but it killed all 4 sensors.

 If still OK, heat for two full minutes and watch for drops in voltage. Sometimes, the internal connections will open up under heat. http://www.scottykilmer.com/
 If the sensor is OK at this point, and will switch from high to low quickly as you move the flame, the sensor is good.  (  think , it might be good, nobody can really test sensors fully on any bench)

Many bad slow and biased sensors pass this test.
To me its just a waste of my time and fuel.
 When replacing a sensors, don't miss the opportunity to use the test above on the replacement.  (practice makes perfect and 10x on a good one)
This will calibrate your evaluation skills and save your money in the future.


v2  (all red neck , backwood, or max shade tree,  testing , nothing really serious but can work in a pinch or stuck)

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