Oxygen Sensor Question

[aa1a]

I have a 99 4runner, 4wd, 3.4l, 5 speed, California model. It has 245K miles and still going strong. But it guzzles fuel. Maybe the 45 mpg in the Prius has me spoiled. Anyway, I've cleaned the MAF and I want to replace the front O2 sensor. I am looking for one online. I can't find one that is for 4wd, California and manual transmission. Can anyone help me with a part number. Also, the sensor is easy to reach but the connector is tucked way up between the tranny and the body. It looks like it may only be accessible from the top through the shift boot. Has anyone replaced one of these and could offer advice.
Thanks,
Jim

 

[TheDurk]

I have a 99 4runner, 4wd, 3.4l, 5 speed, California model. It has 245K miles and still going strong. But it guzzles fuel. Maybe the 45 mpg in the Prius has me spoiled. Anyway, I've cleaned the MAF and I want to replace the front O2 sensor. I am looking for one online. I can't find one that is for 4wd, California and manual transmission. Can anyone help me with a part number. Also, the sensor is easy to reach but the connector is tucked way up between the tranny and the body. It looks like it may only be accessible from the top through the shift boot. Has anyone replaced one of these and could offer advice.
Thanks,
Jim

As you can see by my sig, I have the same truck, also a Cali. The sensor in the front is a wideband air/fuel sensor Denso 234-9003. In recent years, Amazon has had the best price. This is the identical OE sensor without the red box:

Amazon.com: Denso 234-9003 Air Fuel Ratio Sensor: Automotive

The swap is easy, if you unbolt the sensor FIRST! Then you can pass the sensor up where the connector is and let everything fall down the other side. The connector will then hang down where you can get to it easily. To install, just reverse, plug in the connector, and pass the sensor back over the top. It took me an hour to figure this out--I have never seen it in any of the DIY write-ups. They are all written for different trucks and want you to undo the connector first.

If you need new nuts (I did), they are part no. 90179-08059 at the dealer or any good stainless M8-1.25 nut you can find.

 

[aa1a]

Thank you Dirk for the info. You saved me a lot of pain. I'll get some stainless nuts too. Did you do the rear sensor also? I understand the front one affects the fuel mileage. I had a check engine light a while ago but cleaning the MAF fixed that. The dealer replaced one sensor at 100k miles but I'm not sure which one.
Jim

 

[TheDurk]

Thank you Dirk for the info. You saved me a lot of pain. I'll get some stainless nuts too. Did you do the rear sensor also? I understand the front one affects the fuel mileage. I had a check engine light a while ago but cleaning the MAF fixed that. The dealer replaced one sensor at 100k miles but I'm not sure which one.
Jim

No, but eventually I was getting a P0420 (maybe 15k after the front one died) so it got done on its own. That solved the p0420. It was a Denso 234-4153. No reason to do the rear unless you are getting a code. All they do is set codes; they have no effect on how the engine runs. Even at 145k and no codes, your front one is due for a swap--you may well see an improvement in mpg. They can degrade without throwing codes after as little as 80k.

 

[4x4mike]

I have the same truck and did a little write up as the result of trouble code P0125.

Here is my write up on Ultimate Yota, with some pictures and part number.
http://www.ultimateyota.com/showthread.php?9623-Trouble-Code-P0125

I got the code without the decrease in fuel mileage. I was about to leave on a trip, didn't want to travel with the code so I went to the dealer for the part. From what I've read and heard you want to go with a factory part as it will last longer.

My 5 speed transmission made the replacement of the sensor of PITA. I ended up having to go through the top of the transmission tunnel and I believe I had to break the clip that held part of the wire. I was quite sore from the wrestling I had to do while holding an inspection mirror, flashlight and seal pick.

TheDurk posted that the sensor will fall with the sensor, not on my truck. It will do that now because I broke the clip which makes me believe his has been changed before. The clip is held on with a bracket that is held in place with a bolt on top of the transmission. That was hard to access plus the plug for the sensor had a kung fu grip and would not release.

It's been some time but my mileage was only super good for less than 1000 miles. It's back to about where it was, as in it didn't make a huge difference.

 

[TheDurk]

I have the same truck and did a little write up as the result of trouble code P0125.

Here is my write up on Ultimate Yota, with some pictures and part number.
http://www.ultimateyota.com/showthread.php?9623-Trouble-Code-P0125

I got the code without the decrease in fuel mileage. I was about to leave on a trip, didn't want to travel with the code so I went to the dealer for the part. From what I've read and heard you want to go with a factory part as it will last longer.

My 5 speed transmission made the replacement of the sensor of PITA. I ended up having to go through the top of the transmission tunnel and I believe I had to break the clip that held part of the wire. I was quite sore from the wrestling I had to do while holding an inspection mirror, flashlight and seal pick.

TheDurk posted that the sensor will fall with the sensor, not on my truck. It will do that now because I broke the clip which makes me believe his has been changed before. The clip is held on with a bracket that is held in place with a bolt on top of the transmission. That was hard to access plus the plug for the sensor had a kung fu grip and would not release.

It's been some time but my mileage was only super good for less than 1000 miles. It's back to about where it was, as in it didn't make a huge difference.

I am original owner. The A/F was original. The clutch had been replaced previously at a transmission shop, so it is possible that it was de-attached at that time when they dropped the tranny. If so, they did me a favor.

Wow, you paid $267 for that sensor? $113 at Amazon for the exact same thing. There is no "it will last longer" about it. It's just a red cardboard box. Denso made the OE sensor and the one from the factory is the same one they sell.

 

[4x4mike]

I am original owner. The A/F was original. The clutch had been replaced previously at a transmission shop, so it is possible that it was de-attached at that time when they dropped the tranny. If so, they did me a favor.

Wow, you paid $267 for that sensor? $113 at Amazon for the exact same thing. There is no "it will last longer" about it. It's just a red cardboard box. Denso made the OE sensor and the one from the factory is the same one they sell.

If it were my truck, yes that would have been a favor.

I paid $267 because I was already behind in prepping to leave town with a newborn. I was leaving on a near 900 mile trip with the family and didn't have the time to wait or want to hassle with vehicle problems. At the time the cost wasn't something that was going to keep me from making the repair.

The lasting longer part is in regards to OEM which is Denso. A brand to avoid is Bosch, for example.

 

[02SE]

The connector for the front O2 sensor on my '97 V6, 5speed, was also attached to the top of trans. I found it easiest to access it through the shifter hole in the body, after removing the interior trim. It would help to have small hands (which I don't) to access the connector. So I got creative with tools instead.

Durk, if yours would just fall down to where it was accessible after passing the sensor over the top of the trans, then I'm guessing the transmission shop either broke the clip, or just didn't reattach it.

I thought about leaving mine unattached to the top of the transmission case, but decided that a little inconvenience every 100K+ miles, was better than having the wires flopping around, potentially fatiguing and breaking the wires, which could lead to a CEL and diagnostic hassles down the road.

For the OP, I also bought my Denso before (bank 1 sensor 1) and after cat (bank 1 sensor 2) O2 sensors from Amazon. Denso is a subsidiary of Toyota, and the Denso O2 sensors are OEM. I paid $109.00 shipped for both, a couple years ago. None of my friends that are still in the auto repair business could touch that price.

In my case the rear sensor set a CEL, and since I needed to have no CEL's to pass our annual emissions test, I replaced it. I decided to replace the front since after testing it, it proved to be a little lazy, but hadn't set a CEL yet. After replacing the front sensor, the MPG noticeably improved.

 

[TheDurk]

The connector for the front O2 sensor on my '97 V6, 5speed, was also attached to the top of trans. I found it easiest to access it through the shifter hole in the body, after removing the interior trim. It would help to have small hands (which I don't) to access the connector. So I got creative with tools instead.

Durk, if yours would just fall down to where it was accessible after passing the sensor over the top of the trans, then I'm guessing the transmission shop either broke the clip, or just didn't reattach it.

I thought about leaving mine unattached to the top of the transmission case, but decided that a little inconvenience every 100K+ miles, was better than having the wires flopping around, potentially fatiguing and breaking the wires, which could lead to a CEL and diagnostic hassles down the road.

For the OP, I also bought my Denso before (bank 1 sensor 1) and after cat (bank 1 sensor 2) O2 sensors from Amazon. Denso is a subsidiary of Toyota, and the Denso O2 sensors are OEM. I paid $109.00 shipped for both, a couple years ago. None of my friends that are still in the auto repair business could touch that price.

In my case the rear sensor set a CEL, and since I needed to have no CEL's to pass our annual emissions test, I replaced it. I decided to replace the front since after testing it, it proved to be a little lazy, but hadn't set a CEL yet. After replacing the front sensor, the MPG noticeably improved.

Yours is a different setup. There were no Cali's in '97 and the front O2 is in a different place with only one cat. On the Cali. it's up on the vertical and the wires are shorter. It doesn't seem to flop at all. But 4x4Mike obviously has the Cali. layout since he uses an A/F. You learn something everyday. Anyway, I'm leaving it the way it is. 90k since the clutch went in, and no problems yet.

 

[02SE]

Yours is a different setup. There were no Cali's in '97 and the front O2 is in a different place with only one cat. On the Cali. it's up on the vertical and the wires are shorter. It doesn't seem to flop at all. But 4x4Mike obviously has the Cali. layout since he uses an A/F. You learn something everyday. Anyway, I'm leaving it the way it is. 90k since the clutch went in, and no problems yet.

Yes, I knew my '97 has a bit different emissions system than your '99, and 4x4mike's later model. I was just thinking if your sensor wires were not held securely in place as designed by Toyota, the wires might be subjected to enough movement, that they could eventually fatigue and break.

Anyway, it sounds like you're probably good if it hasn't caused an issue by now.