O2 (Air/Fuel Ratio) Sensor Replacement, Bank 1 - 5VZ-FE, w/ Manual Transmission

About a month ago I pulled into the QT in Rock Hill, SC because gas was an insanely cheap $1.67/gallon. I filled up the tank and before I could pull out of the parking lot my CEL lit up bright and orange. I'm not sure if that was just a strange coincidence or not but it meant a detour to the parts store for a free code reading was in order. The truck registered a P0031 code which is the Oxygen (A/F) Sensor Heater Control Circuit Low (Bank 1 Sensor 1).

I looked through the site and didn't see a tutorial specific to the 5FZ-FE w/ manual transmission so I figured it's about time I did my part and add a little more information to TW so here we go.*

*Please note, I am not a Toyota Certified Technician, I'm not a mechanic period. This is a fairly simple procedure if you know how to turn a wrench. That said, if you decide to follow a "how-to" on the internet you're responsible for the outcome.

Step 1. Locate your 02 sensor

Before you read any further, this is for the first gen 3.4L engine with a manual transmission. If that's not what you're driving this isn't the thread for you. There will be slight differences mainly in location of components and part #'s between this setup and others. Your sensor will be located between your catalytic converter and downpipe at a 40 degree angle pointing towards your driver side. I chose the Denso part #

$170 234-9003 Air Fuel Ratio Sensor

234-9003 because the consensus on TW is that OEM parts are the way to go. I got mine on AutoAnything.com for around $20 less than the local parts store with free shipping.



Step 2. Loosen the nuts

The two nuts holding this on have been subjected to years of abuse, mud and heat so you have to loosen them. I sprayed mine with PB Blaster once a day for three days prior to working on it while waiting for the part to come in. It should go without saying but, you will be spraying chemicals above your face into filth. Be smart, wear some sort of eye protection.



Step 3. Into the cab

The electrical connection for the 3.4L w/ manual transmission is above the transmission, impossible to reach from underneath. To disconnect you have to come at it from above. Remove your manual transmission and 4WD transfer case shifter knobs.



Step 4. Remove the Console

The plastic cover around the shifter boots is held in place by four Phillips head screws. Remove these screws and carefully pull the console towards the dash and up. Once off, clean the decade's worth of coffee and dirt off it. Don't eat the french fry you find underneath.



Step 5. Remove the Shifter Boots

Beneath the plastic console and boot covers are the rubber shifter boots and four more Phillips head screws. Remove the screws and pull the boot plate out.



Step 6. Electrical Connection

The electrical connection that your 02 sensor, bank 1 is plugged into is held in place with a clip and pointing towards the engine. It can be found by reaching into the opening on the end nearest the dash. It is impossible, for me anyway, to disconnect without removing it from the clip.*

*I've seen online where people say you should disconnect the battery before unplugging the O2 sensor and others say you don't. I disconnected the battery before going any further. At worst, I have to reset my stations and the clock I can't see behind the steering wheel.



Step 7. Release from Clip

Using a small flat head screwdriver, push the clip in on the right side of the electrical connection. Carefully jiggle it out. I found that using my phone's camera to see what I'm doing and the flashlight on it were helpful. As you've no doubt figured out by now, space is tight.



Step 8. Disconnect from the Exhaust

Get back under the truck. The two nuts you've been spraying with PB Blaster are now ready to be removed. The bolt closest to you is a breeze. The one closer to the transmission is kind of a pain. If you put the socket at the angle I have in the picture it is possible, albeit slow. If you have tools that work better please put in the comments what you used.



Step 9. Fish the 02 Sensor up into the Cab

Pull the O2 sensor off the two bolts, make sure to remove the gasket and get back in the cab. Grab the end with the electrical connection and pull the sensor up into the cab.



Step 10. Disconnect the O2 Sensor

Now that the sensor is no longer clipped to the transmission and the part is pulled into the cab the electrical connection is at an angle where it's possible to disconnect without donking up your hand or the connection. Using your flat head screw driver again, push the clip out and carefully disconnect the sensor from the connection.



Steps 11 - Beer.

The hard part is over. Now you need to plug your new O2 sensor into the connection, put the sensor back through the hole, stick the electrical connection back to the clip on the transmission (if you didn't get pissed off and just snap it off) crawl underneath and put the new gasket and sensor back into the exhaust location over the two bolts. Use the original nuts and tighten it back. Connect your battery. Start up the truck and check you CEL. Mine cut off immediately. Put the shifter boots back on attaching with the four screws, put the console back on attaching with the four screws, test drive, park it, remove keys, shut door, open fridge, consume beer.

 

Great write up! Though, I was under the impression that Toyota called that sensor the Air/Fuel sensor, and not an O2 sensor?

 

Informative write-up, good pix, and nicely written !

 

Thanks McMash. It's 6 of 1, half a dozen of the other. The correct term for the bank 1 sensor in front of the catalytic convertor is the air/fuel sensor but when you go to the parts store to pick it up or even search the part # online a lot of places are calling it an oxygen sensor. I'm going to edit the title regardless.

Here's a better explanation I found:

The ECM uses an oxygen sensor to ensure the air/fuel ratio is correct for the catalytic converter. Based on the oxygen sensor signal, the ECM will adjust the amount of fuel injected into the intake air stream.

There are different types of oxygen sensors, but two of the more common types are:

• the narrow range oxygen sensor, the oldest style, simply called the oxygen sensor.

• wide range oxygen sensor, the newest style, called the air/fuel ratio (A/F) sensor.

Also used on very limited models in the early 90s, was the Titania oxygen sensor.

OBD II vehicles require two oxygen sensors: one before and one after the catalytic converter. The oxygen sensor, or air/fuel ratio sensor, before the catalytic converter is used by the ECM to adjust the air/fuel ratio. This sensor in OBD II terms is referred to as sensor 1. On V-type engines one sensor will be referred to as Bank I Sensor 1 and the other as Bank 2 Sensor 1. The oxygen sensor after the catalytic converter is used by the ECM primarily to determine catalytic converter efficiency. This sensor is refer-red to as sensor 2. With two catalytic converters, one sensor will be Bank 1 Sensor 2 and the other as Bank 2 Sensor 2.

 

'preciate it skeezix!

 

Very interesting, thank you! When it comes to OBD2 stuff, I am lost. I didn't realize they were the same part. Toyota had different part numbers for them, and the front one was CONSIDERABLY more expensive, for whatever reason.

 

No you're right they are different parts and the bank 1 sensor is more expensive. Just some people people still call them both O2 sensors.

 

Marking - my truck threw a P1135 CEL.

 

Just replaced my O2 sensor with the help of this thread, it was very helpful. Probably cut my time in half! Step 11 was my favorite though!

 

I'm glad it was helpful!

 

I just did this last month on my 2.4. The only problem I had was removing the nuts off the bolts. They were rusted completely round and I was forced to file them down so I could get a wrench around them. I installed the sensor and then covered the bolts with after anti sieze prior to putting the nuts back on. I didnt have to pull the shifter cover as the 2.4 has a larger cable. I used OEM denso sensor as well.

http://densoautoparts.com/find-my-part/vehicle-selection

 

Awesome write up! I used Denso sensor which looked a lot different from the unmarked POS aftermarket one the PO put in it.

Also I used this pivot attachment for the bolt closest to the transmission and worked great Also found a nice ball of stuff

 

Ooh that pivot attachment would’ve been nice. I’ll have to get one of those. Thanks for adding that for future reference!

 

After much internet research and YouTube videos, I had given up on finding the connector even after accessing from inside the cab. One last check before calling a mechanic led me to this posting which was exactly my Taco model. Instructions and photos were right on, and I finished the replacement in 30 minutes, easy-peas. The hardest step for me was getting the darn clip removed, but after that, a breeze, CEL cleared and running smooth now. Thanks for saving me several $$.

 

That’s great man, glad it helped!

 

Hey hey ! Finally I came across the right thread here.... I have a 2003 Tacoma 6cyl manual transmission and I had been scratching my head why I couldn't see the electrical connection for this thing and why I felt
it running to / on top of the transmission. Yes, this explains it all ! Can anyone confirm again the Denso part number - Densso

$170 234-9003 Air Fuel Ratio Sensor

234-9003 - This is specific for manual transmisisons? I called the dealer to try and verify, and they said that part number comes up on their end but didn't necessarily say for manual transmissions. I think it's the right one though ? Seems to be as the cabling looks/ feels longer than the pics I see for folks doing this with automatic transmissions where the electrical connection is all down below, a bit easier to tend with. Thanks in advance!!

 

Best Denso part look up and to purchase identical replacements
https://densoautoparts.com/find-my-part.aspx

 

ok well here is a fun one... so I have an 03 Tacoma 6 cyl, TRD, manual transmisson and while I was changing out the upstream O2 sensor (this thread was great), when removing the shift knobs (because I am dumb and didn't even think about it) I severed the wire inside the knob that is for the on the fly 4wd button trigger. How you even get this knob off without severing this wire is beyond me. And now I have this severed connection and the 4wd wont engage because, well, the severed wire. Fun. I am digging into this now to see how it gets fixed but if anyone has any insight, I am all ears. It looks like there is a plug connection downstream from this but how you would even get at without removing the knob seems odd too ?

 

Anybody if this would be the same for an Automatic?

 

Crap. I'm about to do exactly what you did. Did you find an answer to pulling your knob off safely?