Oxygen Sensor Air/Fuel Sensor Heater Resistance

I'm showing the difference in resistance between two air/fuel sensors that can fit the same vehicle. One will set a check engine light, but the other will not. Same method applies to regular oxygen sensors.

[@RomanAutomotive]

When I was saying about the sensor being open, and there being not resistance, that is incorrect. If heater circuit is open, the meter will read out of limits, not 0 resistance.

[@frankvasquez1387]

Roman, thanks for the good information! Something to really watch out for! Good Job!

[@seekers28]

My car is having a lean issue,both upstream sensor bank 1 and 2 is new but i still got a code 25,both bank too lean with scanner,and its reading 0.00mV at live data stream..any idea whats happening?seems like the ecu is ignoring the new o2 sensor

[@mckoylach1622]

Does this procedure applied to the 2010 pilot sensor also? I have two codes,P0135 and P0155 . Thanks

[@greddyt05]

Quick question for you. Do you know if it's possible too install an ohm resistor into the harness for the sensor by the catalytic converter so that you can leave the sensor unplugged and not show a code? As a way of tricking the computer.

[@RomanAutomotive]

I would think that is a possibility. The downstream sensor usually should stay sturdy

[@rodzodrizzle1386]

If you put a resistor on what about the fuel trims

[@shawnthaxton9182]

Just tested my 2 black wires on my 07 camry have nothing reading(OL) sensor looks to been replaced at one time. looks newer thinking it has failed have p0031

[@scooter12368]

do all cars have fuses for 02 sensor. got a 0053 code so i unplugged upstream sensor and car chevy aveo 2011 and it ran well. concluding bad o2 sensor. i did get 12 volts through the harness bought another sensor, no harness with it. i wired the new one. same problem, car runs well after warm up engine dies. i unplug new sensor and it starts running well again. can you give me a direction to follow. i have volt meter and test light only. fuse box inside doesn't indicate any fuse for 02 sensor. haynes, chilton has no manual for that car. i did change plugs 4 weeks earlier, no codes at time and car running well. just did a maintenance thing. thanks

[@billvillanueva6729]

i tried to test the resistance of my downstream 02 sensor and i got about 14ohms, what is the normal resistance of downstream o2 sensor? I have a p0420 code always showing everytime at an idle.

[@adamrozman]

Hi! Did you figure out if it was the o2 sensor?

[@adanarceo4636]

So the normal homs for pretty much every o2 sensor should be between 2.5 to 4.0 homs. Thanks in advance sir. 👍

[@charlesdavis4396]

Your using a Harbor freight $3.00 multimeter. Is using s Fluke meter the same??

[@roltyd22]

Is 1.4 considered bad?

[@laprepper]

Having this same issue. The manufacturer said that some times different generation of sensors cause issues with the ECU?

[@laprepper]

I'm presently on the 3rd sensor on B2S1 and the second sensor on B1S1, both upstream (my car only has 3). None of them are Denso, all of them are Kwiksen (except the lower rear, or 3rd one)

[@thegfxmech5475]

The weirdest thing is going on with my 09 Tacoma. P0031 says it's sensor 1 bank 1 which is the upstream sensor. However when doing a resistance check on the before the cat sensor I get a 2.4ish ohms(3.5 limit) I checked the after cat sensor just out of curiosity and that is way off with 14.5ohms. Why would the code scan give me the wrong sensor??

[@snipsey2]

Jo G Hey did you ever get this figured out? Running into the same problem with my ‘05 Taco. I’m getting P0430 code which is Bank 2, it just doesn’t say which sensor. Testing the before cat sensor I get 2 ohms, and the after cat sensor reads at 13-14ohms. I was thinking my before cat sensor was bad. Was was the issue with yours?

[@paulmonk7820]

@@snipsey2 I think there should be three sensors, two upstream (bank 1 and bank 2), and 1 downstream. The resistance readings you got seem to be OK for b1s1(air-fuel ratio) and b1s2(oxygen). The sensor for bank 2 is also AFR, and is located in the exhaust between the other two. Also, the problem could be with the wiring for the heater circuit, or a blown fuse. Not sure if both AFR sensors run off the same fuse.

[@howtodoitdude1662]

I believe you need to isolate the sensor from the car. You tested two sensors in two different locations.

[@AutumnsAdventure15]

Harbor freight free meter for the win

[@padams8485]

Jerry Smith, Oh yeah Harbor Freight, nice. My Earthquake XT 1/2 inch impact works great too. . Never had a bolt it couldn't break lose with ease.

[@danditiello4846]

ty

[@gabrielchukwuka1493]

pls what should be the resistance on a 2000 Camry air fuel ratio sensor?

[@leonvetti6724]

1. 5 to 1.8 not more than 2. if your AF shows 00 that means no resistance exactly like any wire. And if the meter reads more than 2 Ohns, it is Open, the current is not passing and you need to change the sensor, but before that check the integrity of the harness which is connected to the ECM.

[@certaindeed]

That;'s why it's good to use the factory OEM manufacturer parts, unless you are very very very familiar with different replacement specs etc. In order to test this correctly you would have to power them up as well to temperature and measure the current and use R=V/I to determine the true operating characteristics, as those can be a couple of ohms different between brands. Otherwise you can spend way more money in labor messing around with this stuff. On your own is fine, on the customer clock never.

[@laprepper]

you mean "back probe"?

[@MrYosmitty]

a genius like you using a harbor freight multimeter. that shows mechanics don't make enough money. haha

[@certaindeed]

+terminal velocity He's good, though.

[@seekers28]

Fuse? Heater circuit have fuse?

[@alexwolf8019]

Yes, if you look in your manual you should see the fuse location. Its normally in the engine compartment fuse block.

[@mr.iforgot3062]

I urinated on the sensor than hit it with a ball peen hammer. It didn't fix the sensor at all. I decided to cut the wires and solder 1/2" copper tubing to make it perform better but that didn't work either. Must be a faulty unit.

[@vangoventures6513]

jesus man, invest in a real DVM...lol