Author Topic: First auto DIY - help me replace my oxygen sensor  (Read 2645 times)

homestead neohio

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First auto DIY - help me replace my oxygen sensor
« on: January 23, 2016, 11:01:06 AM »
I have a 2000 Toyota Tacoma 4cyl automatic, 97k miles, with a check engine light on.  I had codes read and they said to replace the oxygen sensor.  I didn't realize there were 2 sensors, now I'm trying to figure out which is the problem.  The auto parts guy didn't say which it was when selling me a single sensor.  I physically found both sensors, one on either side of the catalytic converter.  Limited youtube search suggested failed senors will fail a continuity test.  When I tested both upstream and downstream sensors, neither failed continuity. 

Upstream sensor 127 ohm, downstream is 135 ohm.
The new sensor is 9.5 ohm. 

Does this mean that downstream is worse due to higher resistance?  And the upstream is ready to fail since it is so close?

I called the auto parts place and they did not save the code, so I'll have to go back to have it read again if I want to know which sensor the OBD says is bad.

Also, this is not a spark-plug style sensor, it mounts via two studs and a gasket.  The nuts holding the original sensors on are shot, splitting and ready to crumble.  Is there an easy way to know what size these are so I can get some replacements for the install?  When I get them off, they will be in pieces, so I won't be able to bring one with me.

zolotiyeruki

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Re: First auto DIY - help me replace my oxygen sensor
« Reply #1 on: January 23, 2016, 06:53:44 PM »
The bolts will be metric, almost always an even number of millimeters in diameter and a multiple of 5mm in thread length.  That'll be easy to measure and replace.

The OBD code will indeed tell you which sensor it is which needs to be replaced.  Chances are good that the guy at the parts store sold you the correct oxygen sensor (if there's any difference between the two).  Go ahead and pull the upstream O2 sensor and compare its physical size to the new one to see if they match.  If they match, stick the new one in, plug it in, and see if the problem goes away.  Usually you have to drive a certain number of miles and/or stop/start the car a certain number of times before the code will clear.  If that doesn't solve the problem,  you can swap the new O2 sensor into the rear position and put the old front sensor back in.

JLee

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Re: First auto DIY - help me replace my oxygen sensor
« Reply #2 on: January 23, 2016, 09:23:22 PM »
The bolts will be metric, almost always an even number of millimeters in diameter and a multiple of 5mm in thread length.  That'll be easy to measure and replace.

The OBD code will indeed tell you which sensor it is which needs to be replaced.  Chances are good that the guy at the parts store sold you the correct oxygen sensor (if there's any difference between the two).  Go ahead and pull the upstream O2 sensor and compare its physical size to the new one to see if they match.  If they match, stick the new one in, plug it in, and see if the problem goes away.  Usually you have to drive a certain number of miles and/or stop/start the car a certain number of times before the code will clear.  If that doesn't solve the problem,  you can swap the new O2 sensor into the rear position and put the old front sensor back in.

Toyota generally uses 10, 12, 14, 17, and 19mm.  Oxygen sensors are usually 7/8ths, though - 23mm might fit, but I have a couple of standard o2 sensor sockets that have never failed me.

zolotiyeruki

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Re: First auto DIY - help me replace my oxygen sensor
« Reply #3 on: January 24, 2016, 09:18:12 AM »
The bolts will be metric, almost always an even number of millimeters in diameter and a multiple of 5mm in thread length.  That'll be easy to measure and replace.

The OBD code will indeed tell you which sensor it is which needs to be replaced.  Chances are good that the guy at the parts store sold you the correct oxygen sensor (if there's any difference between the two).  Go ahead and pull the upstream O2 sensor and compare its physical size to the new one to see if they match.  If they match, stick the new one in, plug it in, and see if the problem goes away.  Usually you have to drive a certain number of miles and/or stop/start the car a certain number of times before the code will clear.  If that doesn't solve the problem,  you can swap the new O2 sensor into the rear position and put the old front sensor back in.

Toyota generally uses 10, 12, 14, 17, and 19mm.  Oxygen sensors are usually 7/8ths, though - 23mm might fit, but I have a couple of standard o2 sensor sockets that have never failed me.
Right, but OP said that the sensors don't screw in directly like a spark plug, but rather with two metric bolts.

JLee

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Re: First auto DIY - help me replace my oxygen sensor
« Reply #4 on: January 24, 2016, 01:13:25 PM »
The bolts will be metric, almost always an even number of millimeters in diameter and a multiple of 5mm in thread length.  That'll be easy to measure and replace.

The OBD code will indeed tell you which sensor it is which needs to be replaced.  Chances are good that the guy at the parts store sold you the correct oxygen sensor (if there's any difference between the two).  Go ahead and pull the upstream O2 sensor and compare its physical size to the new one to see if they match.  If they match, stick the new one in, plug it in, and see if the problem goes away.  Usually you have to drive a certain number of miles and/or stop/start the car a certain number of times before the code will clear.  If that doesn't solve the problem,  you can swap the new O2 sensor into the rear position and put the old front sensor back in.

Toyota generally uses 10, 12, 14, 17, and 19mm.  Oxygen sensors are usually 7/8ths, though - 23mm might fit, but I have a couple of standard o2 sensor sockets that have never failed me.
Right, but OP said that the sensors don't screw in directly like a spark plug, but rather with two metric bolts.
Hah, missed that completely. Yeah, hopefully they'll even come out - if they're rusty the heads might snap off.

lthenderson

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Re: First auto DIY - help me replace my oxygen sensor
« Reply #5 on: January 25, 2016, 07:42:40 AM »
When I tested both upstream and downstream sensors, neither failed continuity. 

Your computer waits for your exhaust system to warm up before the sensors kick in to regulate the system. If the sensors don't get up to operating temps in that period of time, they will throw a fault but still have continuity. You can get a OBD unit with graphing software and watch your oxygen sensors over time and see what I mean. I have gotten brand new non-OEM sensors before where their warm up curve isn't the same as the OEM sensors and still throw a fault despite being brand new. I always go with the OEM sensors when replacing them for this reason. I usually just replace both of the at the same time though I would guess the upstream sensor is most likely to fail since is sees worse exhaust conditions than the downstream sensor.