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Oxygen Sensors & Cylinder / Location

For whatever reason, websites don't list sensors as B1/2 and S1/2. They list them in terms of cylinder and location. Here is the breakdown:

B1 = Cylinders 1-3
B2 = Cylinders 4-6

S1 = Front
S2 = Rear

I had my B1S2 replaced with Denso Part 234-4015 earlier month. So far so good.

I hope this helps. Cheers!
 

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Discussion Starter #143
No prob! I haven't updated it in awhile, so if anybody wants to collate the new info, I will amend my original post.
 

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does anyone have an engine bay shot of which one is the b1s1 and b1s2 plugs? i just swapped out my b1s1 with denso universal and the same fault came back on again. wtf?
 

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does anyone have an engine bay shot of which one is the b1s1 and b1s2 plugs? i just swapped out my b1s1 with denso universal and the same fault came back on again. wtf?
No but can take one for you.

B1 is front 3 cylinders, S1 is the uppermost sensor.

What code did you have ???
 

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I got the placement of the sensor figured out. But just not sure if the sensor is plugged into the right part of the engine harness. there are two plugs near the front passenger side of the cylinder head. how do i know which one b1s1 plugs into and which b1s2 plugs into? When my sister owned the car, she brought it to a shop to fix this issue and they changed all the o2 sensors and exhaust mani but still coming up with o2 faults. i just swapped out the b1s1 sensor and p0135 popped up again..
 

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I got the placement of the sensor figured out. But just not sure if the sensor is plugged into the right part of the engine harness. there are two plugs near the front passenger side of the cylinder head. how do i know which one b1s1 plugs into and which b1s2 plugs into? When my sister owned the car, she brought it to a shop to fix this issue and they changed all the o2 sensors and exhaust mani but still coming up with o2 faults. i just swapped out the b1s1 sensor and p0135 popped up again..
Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)

So you need to check the resistance and continuity in the sensor, if that is OK then check the voltage (power side) and ground path on the low side of the connection.
search for the proper procedures.

Others that have had this problem have posted threads on here, heater circuit problems seem quite common.
 

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Can someone confirm which plug is suppose to be for b1s1 and b1s2?
Ok on my 2004 the lower one, looks more grey and loose in your pic, goes to B1S1

BTW both mine are the same grey color .....both attached to the bracket on my car.

Its easy to follow this wire to the Sensor.
 

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Hi guys..my car's engine light turned on few days ago...it is P0057 H02S Heated Oxygen...Sensor control circuit low (bank 2 Sensor 2)...does anyone know how to fix it or any DIY or know where i can buy the part?
 

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heater circuit malfunction

I followed your directions which were great by the way, but my problem continues. I did a code read after installing the new b1s2 oxygen sensor made by lexus and the code reads p0141. What I want to know is WHERE is the "heater circuit?" nothing more nothing less, a picture by anyone would be great. I am assuming the heater circuit is the connector attached to the oxygen sensor.

alvaro quinonez
 

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I followed your directions which were great by the way, but my problem continues. I did a code read after installing the new b1s2 oxygen sensor made by lexus and the code reads p0141. What I want to know is WHERE is the "heater circuit?" nothing more nothing less, a picture by anyone would be great. I am assuming the heater circuit is the connector attached to the oxygen sensor.

alvaro quinonez
The heater circuit is a part of the 02 sensor. Inside of an O2 sensor is a sensor signal circuit and a heater circuit. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The two black wires on an OEM Denso sensor are the heater wires and should read about 10-14 ohms @68*F, IIRC.

P0141 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor2)

Replacing the correct sensor should have solved the problem. Check to see if the connection harness is tight(by the air box) and possibly reset/clear the code by pulling the negative off the battery for a few minutes. Other than that, they either replaced the wrong sensor or the new one is bad, which they should replace free of charge.
 

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The heater circuit is a part of the 02 sensor. Inside of an O2 sensor is a sensor signal circuit and a heater circuit. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The two black wires on an OEM Denso sensor are the heater wires and should read about 10-14 ohms @68*F, IIRC.

P0141 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank1, Sensor2)

Replacing the correct sensor should have solved the problem. Check to see if the connection harness is tight(by the air box) and possibly reset/clear the code by pulling the negative off the battery for a few minutes. Other than that, they either replaced the wrong sensor or the new one is bad, which they should replace free of charge.
Jason, so whats does the P0036(same sensor)code refer to?
 

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Jason, so whats does the P0036(same sensor)code refer to?
There are at least 5 related codes just for that sensor's(B1S2) heater circuit. That's because our ECM is that damn sensitive. Normally any of these codes would indicate the heater circuit is open, shorted, or simply malfunctioning. I would check the connections and if they look ok, then I would replace the sensor and clear the code.

P0054-O2 sensor heater resistance B1S2
P0036-O2 sensor heater control circuit B1S2
P0037-O2 sensor heater control circuit low B1S2
P0038-O2 sensor heater control circuit high " "
P0141-02 sensor heater malfunction
 

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There are at least 5 related codes just for that sensor's(B1S2) heater circuit. That's because our ECM is that damn sensitive. Normally any of these codes would indicate the heater circuit is open, shorted, or simply malfunctioning. I would check the connections and if they look ok, then I would replace the sensor and clear the code.

P0054-O2 sensor heater resistance B1S2
P0036-O2 sensor heater control circuit B1S2
P0037-O2 sensor heater control circuit low B1S2
P0038-O2 sensor heater control circuit high " "
P0141-02 sensor heater malfunction
Cool.. THNX!
 

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Hello All,
I have been lurking for about a week and wanted to post on here to make sure I get the right O2 sensor and have the right location. The Code im throwing up is a P0430 Catalyst System Efficency Below Threshold (Bank 2). I have been reading on this forum and using the search function to make sure I have the right location and right sensor but want some reassurance. Is this O2 sensor it is identifying the one under the passenger area that you can plainly see and that some have removed the seat to get to it easier? I want to verify before I start taking one out and changing it. From what I have read this is the right location. I am at Densoproducts and sparkplugs.com and on eBay and want to verify im looking at the right o2 sensor too. Since the dealer wants 190 for this sensor, i'm going to try and change it for cheaper :)
Densoproducts.com shows Front cylinders 4-6, front upper cylinders 1-3 , rear cylinders 1-3 and rear cylinders 4-6. It doesnt mention the one after the cat (downstream I guess) . This is the one im looking at on ebay New Rear Bosch O2 Oxygen Sensor Lexus IS300 2002 2001 Parts Auto Car | eBay
I bought the car a week and a half ago and have unplugged the batt 2 times and cleared the code twice. The same code keeps popping up. I ran seafoam in the tank as well. I test drove the car 3 times and it never came on. I got 91 gas in it (previous was putting 87 in mostly and occasional 91) and about 20 miles later the light came on.
Thanks again to the community for your help
BTW its a 2001 Lexus IS300 with 203k miles. (high miles I know, but I had faith in it, no leaks no burning)
 

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Hello All,
I have been lurking for about a week and wanted to post on here to make sure I get the right O2 sensor and have the right location. The Code im throwing up is a P0430 Catalyst System Efficency Below Threshold (Bank 2). I have been reading on this forum and using the search function to make sure I have the right location and right sensor but want some reassurance. Is this O2 sensor it is identifying the one under the passenger area that you can plainly see and that some have removed the seat to get to it easier? I want to verify before I start taking one out and changing it. From what I have read this is the right location. I am at Densoproducts and sparkplugs.com and on eBay and want to verify im looking at the right o2 sensor too. Since the dealer wants 190 for this sensor, i'm going to try and change it for cheaper :)
Densoproducts.com shows Front cylinders 4-6, front upper cylinders 1-3 , rear cylinders 1-3 and rear cylinders 4-6. It doesnt mention the one after the cat (downstream I guess) . This is the one im looking at on ebay New Rear Bosch O2 Oxygen Sensor Lexus IS300 2002 2001 Parts Auto Car | eBay
I bought the car a week and a half ago and have unplugged the batt 2 times and cleared the code twice. The same code keeps popping up. I ran seafoam in the tank as well. I test drove the car 3 times and it never came on. I got 91 gas in it (previous was putting 87 in mostly and occasional 91) and about 20 miles later the light came on.
Thanks again to the community for your help
BTW its a 2001 Lexus IS300 with 203k miles. (high miles I know, but I had faith in it, no leaks no burning)
Yes, P0430 is bank 2 sensor 2 is a cat efficiency code. It can be caused by a cat going bad, an exhaust leak, or bad o2 sensor. It is easier to check for leaks and replace the O2 sensor, even though the sensor can be tested with a voltmeter to verify it's .2 to .9 volt fluctuation. You don't nessesarily have to remove the front seat. I know some members have moved the seat forward and up all the way and had enough room to pull the old sensor wiring out and fish the new sensors wiring in. It is located at the Y pipe, directly below the seat. If you do remove the seat, make sure to disconnect the battery and wait a few minutes before doing any work, this is to prevent the airbags from deploying when the seat harnesses are disconnected. IMO, I would go with an OEM Denso replacement, but Bosch is fine and that link looks like the correct sensor. This image here shows all the o2 sensor locations and the part numbers to replace them with.

Http://img522.imageshack.us/img522/8813/o2diagram16.jpg
 
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