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Discussion Starter #1
Hello All ! I am new member here although have been reading for a while. But this is my first post seeking help. So here is the dilemma:

I've been driving this 2006 RAV4 for a few years now. Recently shot me with a bunch of error codes. Check Engine, VSC and 4WD all three together. Stayed on for 50/60 miles then went off. A few months later the same symptom again. I went to the mechanic shop but before I get there the lights went off. Came back again after a few months later. This time I had the mechanic check OBDII and told me I needed a O2 sensor for B1S2 (as far I remember) which is the downstream O2 sensor after Catalytic Converter. I looked up and found the part number would be 234-4622. I am okay with that far.

I don't have much knowledge about cars but I didn't want to jump into spending before understanding the issue. And so I looked up further and found the location of the sensor would be under the driver side removing the carpet will reveal the jack where the sensor connector would be hooked up and then the wire goes thru the floor down underneath and then the sensor is screwed into the pipe after the CC. I followed the instruction but instead of the sensor jack I found something that to me looks like the connector where the sensor is supposed to be hooked up with. Yes, the pictures of part # 234-4266 looks very much like connects to this thing here I posted some pictures I took from my car. This thing also has four wires connected to it just like the real O2 sensor should have. Well, not only that, there is also a hole in the floor blocked with plastic grommet (i circled in red) that looks like the hole thru where the sensor wire should go under the car floor !

Does it mean my car did not have the O2 sensor ? I have been driving this car without the O2 sensor for years and now it is telling me that my O2 sensor is bad ?? I am really shocked and surprised. What am I missing here ? Please enlighten me..
 

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You need to tell us if you have 4 or 6 cylinders
this is for v6


For 4cylinders. This is for 2010 but it might be the same on 2006

 

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Re: The first video

You need to tell us if you have 4 or 6 cylinders
this is for v6

RAV4 Replace Bank1 Sensor2 (B1 S2) Oxygen Sensor Toyota 2007 V6 - YouTube

For 4cylinders. This is for 2010 but it might be the same on 2006

Locating RAV4 2010 Oxygen Sensor Bank 1 Sensor 2 - YouTube
I just came back home and stumbled upon the first video from your post. That video matches exactly with my scenario except for the O2 sensor. The hole in the so called firewall in the video where the sensor connector came out from is the hole in my picture I circled in red. And the location of the connector in the video is exactly what I suspected to be the connector. So now that I am confirming 100% that I do not/did not have any sensor at B1S2.

Now, where do I go from there? Since it is a V4, I was expecting 2 sensors for B1S1 and B1S2. But in my case there is no B1S2. Is there a possibility that I might have B1S1 and B2S1 ? Or do I only have a B1S1 and that one is bad ? Do I go ahead and remove the heat shield to check if there is a B1S1 at all ?

Apart from my current problem, I guess not having a B1S2 is not giving any data back to ECU from after the CC, in that case do I need to be concerned about my overall efficiency ? Is it practical to attempt to add a sensor for B1S2 even though it was not there in original design, since the four wire connector is there which, I believe, is already connected to the ECU ?

Thanks in advance!
 

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Now, where do I go from there? Since it is a V4, I was expecting 2 sensors for B1S1 and B1S2.
The engine is an I4 not a V4 and I believe it only has or should have those two sensors since there is no B2.

If the car does indeed not have an post cat sensor then someone must have removed it. The grommet in the feed-thru hole kinda confirms that. Altho unexplained why it's missing it will not affect the engines efficiency since the AFR is set by the pre-cat sensor in the exhaust manifold. The second sensor continuously checks the CC's efficiency for emissions purposes.
What surprises me is that the CE light isn't on all the time. (the VSC and 4WD lights are what we call panic and run to the dealer lights with your CC, credit card in this case.)

I'm currently working on a 2003 Honda Civic where the CE stays on due to a no-heater failure in B1S2. With a new sensor I determined there is no 12V getting to the sensor and a wiring test back to the ECM checks good. That leaves one conclusion - bad ECM. I purchased a used ECM but the car won't start with it due to the immobilizer. The current status is waiting for the owner to have time off of work to drive to the dealer on the old ECM, then I'll install the replacement and have Honda program it to the original chipped key.

Makes me wonder what code your missing sensor is triggering.
 

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Discussion Starter #7
Thanks Dr. Dyno! So you think there was a sensor but someone removed it. If that is true, does it say I can just put a sensor in there regardless of the reason I it might have been removed? Does bad sensor usually trigger error code infrequently and goes by itself after a few days and again come back later on like me ? Since I don't have any light on right now (it was until last wednesday), do you think if I scan now, I can get the correct code? Or should I wait until the next time lights come on?
 

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My Thoughts.....

First off it is unlikely that your RAV was built differently than any other RAV. But lets try to confirm your theory.

The colors of the wires going into the connector for the B1S2 sensor should be Black, Red, Brown, and Black. Can you confirm these are the colors you see?

The image that you provided appears to show male spade connectors, and the images of the Denso PN 234-4266 also seem to show male connectors (at least that's what it looks like on the best photos I can locate). As far as I know electrical connectors still only mate up with the opposite sex.

And finally, rather than making your assumption that the sensor is missing strictly from the interior of your RAV4, why not have a look under the vehicle and see if it has a sensor screwed into the pipe.



 

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Good point Rick L. As far I remember all the Denso 234-4266 has a male connector, then what is another male connector doing here? Well, here the 4 wires I found are red, yellow, black and white. And I actually creeped underneath but could not find any sensor screwed into the pipe. But I can double check and then I'll post back here.
 

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Thanks Dr. Dyno! So you think there was a sensor but someone removed it. If that is true, does it say I can just put a sensor in there regardless of the reason I it might have been removed? Does bad sensor usually trigger error code infrequently and goes by itself after a few days and again come back later on like me ? Since I don't have any light on right now (it was until last wednesday), do you think if I scan now, I can get the correct code? Or should I wait until the next time lights come on?
As Rick says the first thing to check is has the sensor been simply disconnected or did some purposely remove it and plug the hole?

With the Civic disconnecting the sensor gave the CE light within a few seconds of starting the engine. Toyotas could be different so the light is coming on intermittently but once set the code should remain. Either way a look at the sensor or where it's supposed to be is needed.
 

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And I actually crept underneath but could not find any sensor screwed into the pipe. But I can double check and then I'll post back here.
If no sensor there should be an O2-delete plug in its place. Otherwise you'd have a major exhaust leak. It's installed with an Allen wrench.
 

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Thanks Dr. Dyno! So you think there was a sensor but someone removed it. If that is true, does it say I can just put a sensor in there regardless of the reason I it might have been removed? Does bad sensor usually trigger error code infrequently and goes by itself after a few days and again come back later on like me ? Since I don't have any light on right now (it was until last wednesday), do you think if I scan now, I can get the correct code? Or should I wait until the next time lights come on?
simple test is a CEL bulb check, basically are you getting the CEL "ON" when you insert key in ignition and turn to "ON" (not start or crank engine) then when you start the car the light should go out, which is a standard test for all state emission checking of indicator, maybe someone remove the the CEL bulb? it's probably easier to replace the O2 sensor then take apart cluster panel or someone who has knowledge to disconnect at a harness under dash the wire for the CEL indicator? let us know if you get a CEL bulb "ON" check.
 

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Discussion Starter #14
If its a 4cyl go under the passenger door and follow the exhaust pipe up to the front of the car, its near the front wheel and cross member and you will find it.

"ITS NOT ON THE DRIVERS SIDE"
Okay, so here is the game changer. I went underneath again and I actually found a sensor into the pipe, under the passenger side, with four wires, probably black, black, grey, and green hooked up to a connector somewhere under the engine. Unlike what the video shows, the wires did not go inside of the car thru a hole. So apparently I was misguided by the video and was looking at the driver side only, thanks that you mentioned to look at passenger side. So now the question is how do I know what I found here is S2 or S1 ?
 

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Okay, so here is the game changer. I went underneath again and I actually found a sensor into the pipe, under the passenger side, with four wires, probably black, black, grey, and green hooked up to a connector somewhere under the engine. Unlike what the video shows, the wires did not go inside of the car thru a hole. So apparently I was misguided by the video and was looking at the driver side only, thanks that you mentioned to look at passenger side. So now the question is how do I know what I found here is S2 or S1 ?


Bank 1 Sensor 2 is near passenger front wheel just like in the video above. If you did what I said above then you got b1s2

Bank 1 sensor 1 is on the manifold in front of engine when looking with the hood open.
 

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simple test is a CEL bulb check, basically are you getting the CEL "ON" when you insert key in ignition and turn to "ON" (not start or crank engine) then when you start the car the light should go out, which is a standard test for all state emission checking of indicator, maybe someone remove the the CEL bulb? it's probably easier to replace the O2 sensor then take apart cluster panel or someone who has knowledge to disconnect at a harness under dash the wire for the CEL indicator? let us know if you get a CEL bulb "ON" check.
As far as the indicator lights all of those including the CEL are behaving normal except for that periodic interval when CEL, VSC and 4WD stayed on even after the engine crank. If you are suspecting a bad indicator light, it does not look like that since these three indicators are acting in this same pattern for a while. For about first 3 years everything was normal, then these three lights started behaving this way for a few days in every couple of months. And they are still repeating this behavior in the same pattern.
 

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Locating RAV4 2010 Oxygen Sensor Bank 1 Sensor 2 - YouTube

Bank 1 Sensor 2 is near passenger front wheel just like in the video above. If you did what I said above then you got b1s2

Bank 1 sensor 1 is on the manifold in front of engine when looking with the hood open.
Yes that looks like it. But I am still curious what was that I found in the driver side at first ? Is that just an unused option for the B2S2 on a 6 cyl car ? (Although the video1 said it was B1S2)

I am still curious about the pattern of my CEL, VSC and 4WD light. Why dont they stay lit for as long as the faulty sensor is there ? And why do they come one every couple of months and stay on for a few days and then go away without me doing anything ?
 

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I am still curious what was that I found in the driver side at first ? Is that just an unused option for the B2S2 on a 6 cyl car ? (Although the video1 said it was B1S2)
Since the connector in your image was the wrong sex to connect to a Denso sensor, it probably has nothing to do with an O2 sensor. It is most likely for an accessory that your RAV is not equipped with. Any number of things require a 4 pin connector other than O2 sensors.

I am still curious about the pattern of my CEL, VSC and 4WD light. Why dont they stay lit for as long as the faulty sensor is there ?
It is normal for the VSC and 4WD lights to come on anytime the ECU detects an problem with the engine management system (which causes the CEL to come on).

It appears that your problem is intermittent. It could be as simple as a loose connector that disconnects when you hit a large pothole. The connector should be inside the vehicle like every other RAV, so follow the wires and see where it connects. The wires shouldn't be any longer than 12-18 inches, so it shouldn't be difficult.

Once you locate the connector, simply pull it apart and then reconnect it. If that doesn't eliminate the problem then replace the sensor. Perhaps every-time you drive through a puddle and get the sensor wet, the problem occurs until it has time to dry out again.
 

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I kind of liked your explanation Rick L. I actually did followed the wires from my O2 sensor and found that it is connected to somewhere underneath the engine, I stated in my previous post, which is NOT even inside the car. So although it is covered by the hood above but open to the environment underneath. So it makes sense that the connector is prone to get the dirt or water from the road or path holes like you guessed. I'll go check the connector the next good day and if turns out that is the case, I can probably try to seal the whole thing with tape or something right? Thank you all again ! You guys are awsome!
 

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I am still curious about the pattern of my CEL, VSC and 4WD light. Why dont they stay lit for as long as the faulty sensor is there ? And why do they come one every couple of months and stay on for a few days and then go away without me doing anything ?

I had the same problem intermittently, "on and "off for 3 yrs, i have the 07 base model(2nd owner) with no 4wd and the "oil-eater issue" ,did not understand the 4wd light "on"?....no 4wd, anyway got the engine rebuilt under the extended warranty at 155K and then still had those 3 indicators "on/off" intermittently, with that i replace both sensors a/f and o2, i figured those sensors are all "clogged" from all that soot along with the alternator(noisy bearing) and now at 190k ......problem went away. don't know your mileage ,but if over 100k, i generally replace O2 sesnors.
 
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