Oxygen sensors - part numbers (all years) and replacement

[Harbilly]

Does anyone know the part number for a decent oxygen sensor for my 1989 4wd van? It has the one sensor. Before I go to Toyota or the local parts guy and get told the beck-arnley one is $200 or something and nothing else works I thought I would ask!!
Thanks muchly!!!

[timsrv]

Go to www.sparkplugs.com for the best prices on OEM sensors. For pre 88 vans with a single one wire sensor, you would want OEM identical Denso part #234-1056 for about $35.00. For the 88-89 vans with 2 sensors, the OEM identical front 4 wire sensor is Denso #234-4055 and lists for around $70.00. The rear OEM identical sensor is Denso #234-2062 and typically goes for around $100.00. This is a little weird because the front sensor is more complex than the rear (front one has a built in heater). Denso also makes universal O2 sensors that can be used. These are basically the same as the OEM identical sensors except the wire end doesn't match up to your wire harness. For those, you need to cut the wire end off your old sensor and splice it onto the new sensor. Depending on the sensor you need, you may prefer to go this way, as in some cases you will save a lot of money. For the pre 88 vans, you need universal Denso sensor part #234-1057 and they run about $30.00 (not much savings). For the 88-89 2 sensor vans, it would be universal Denso sensor #234-4050 for the front (4 wire) for about $50.00 (big savings) and universal Denso sensor #234-2050 for the back (2 wire) at around $40.00 (huge savings). Tim

[Harbilly]

Thanks Tim.
My Canadian 4wd van has only one sensor. Is that a 4wd thing? A Canadian thing? My rear sensor was removed? Any guesses?

[timsrv]

That's a good question. All of the 88-89 US vans have 2 sensors (one in front of the cat and another behind it). Not sure what they might have done on the Canadian vans. Take a look at the harness connection for the sensor you have to see how many wires it has. If it has only one wire then get the sensor for pre 88 vans. If it has 4 then get the primary (front) sensor for 88-89. Also, if you happen to have the 4 wire sensor then I would suspect somebody removed the rear sensor. Check the pipe behind the cat to see if there's a mounting boss. Also check to see if there's a harness connection for the back sensor (should have a 2 wire plug). Tim

[Harbilly]

Thanks again Tim. The rear pipe isn't factory. I'll dive under tomorrow and look at the wire and post what I find re: front sensor wires!

[timsrv]

The rear pipe isn't factory....................

That could explain a lot. I bet somebody was being lazy and just did away with the rear sensor (rather than fabricate a pipe with a mounting boss). Does it still have a cat?

[Harbilly]

No. It had a cat until it plugged on me last summer and I cut it out on the side of the road and rehung the muffler with bailing wire closer and used tinfoil and wire and clamps to join the cut pipe until the next town where I got a connector pipe and a flange and clamps. I don't recall any mounting spot for a rear sensor anywhere after the cat and I later changed the rest of the pipe and the muffler.
I keep meaning to get a replacement cat but it's, like, 7 on a list of 10 things to do.

[timsrv]

Assuming it originally had 2 sensors on it, it's hard to say how much good it would do to only partially restore the system. The ECU is looking for 2 sensors and adjusts the fuel mix based on the data it sees from them. When a sensor is bad (or not even there) the ECU is blind so it goes back to default settings. Running too lean can damage things so the default settings will intentionally make the van run rich. Running rich means dirty exhaust, poor power, and bad fuel mileage. There's no doubt in my mind that this (and the possibility of a bad TPS) is what caused your cat failure.

I tend to think giving your ECU one "eye" is better than leaving it blind, but ideally it should have 2 sensors and a cat. In addition I would check codes and replace the TPS if that's implicated while doing so. You should also check timing and check and replace any failed VSVs. If it's due for a tune-up, or you're unsure of tune-up history, I would also replace plugs, plug wires, distributor cap, rotor, air filter, fuel filter, etc. I know it's expensive, but there's not substitute for a correctly running van. The 4y performs pretty decent when the emissions system is working correctly. Tim

[Harbilly]

As above:
I agree Tim. You just listed those 6 things on my list!

...and.....

just had a look. Yup, you're the man Tim! The front sensor is a 4 wire and I can see two different two wire plastic plugs near where I would expect to find the harness connection for a rear sensor and nothing is plugged in to them.

So, after my holiday (and driving the van 3600km) I will go see my muffler guy and get a universal cat, new front and rear sensors and a bung to weld on after the cat and 'git r done' in September. Too bad I left this until now as my mileage would improve by 20-25% I bet so that 3600km of summer driving will cost more than it ought to!! ie: I will burn 300-350 litres of gas instead of 225+

I would assume the new rear oxygen sensor will have a plug to fit the end hanging out of the harness so I will be easily able to figure out which of the hanging ends to plug in to as they are of different designs? (one is the same colour plastic as the front sensor connector, and shrouded a bit, one is white and quite open) or am I going to have to did deeper to figure out where to get a part or a connector.

I guess I better go haunt wreckers, unless someone has a pic of the rear connector, where it plugs in and which wire is which (does that matter?)
:cnfsd::dizzy:

[Harbilly]

Tim: just ordered both sensors from the website you listed. Cheaper than anyone up here or ebay. I talked to the wife and she said 'get the ones with ends' so we spent the extra money :cry: since we are missing the harness for the rear. Next time we will get the cheaper splice ins.
We have a rotating mail strike up here but IF the parts arrive within two weeks I'll get them in before I head north.
Getting a universal cat is easy!:)

[timsrv]

Sounds like a good plan. You might also check your EGR parts very carefully because these parts are extremely stressed during a cat failure (excessive temps and pressures occur when the cat gets plugged up). Usually the EGR modulator vacuum diaphragm gets blown. Tim

PS: You picked a good time to purchase OE identical sensors. With the sale they have right now the OE identical front sensor is actually cheaper than the universal one. You could have saved a little on the rear, but since you didn't have the plug anyhow you made the right choice. It will be easy to match up the connectors using the connector on the new rear sensor. Tim

[Harbilly]

Thanks Tim.
I had the intake off a couple years ago and checked out the egr then. Nice and easy with all that jazz off (was changing the injectors). I'm sure I won't enjoy going after the egr now.
I paid:
1 - Denso OE identical O2 sensor
Stock Number: 234-2062
Part Number: 234-2062
Unit Price: $96.80
Extended Price: $96.80

1 - Denso OE identical O2 sensor
Stock Number: 234-4055
Part Number: 234-4055
Unit Price: $48.49
Extended Price: $48.49

Still a bucket of money but, hey, what can a fellow do?? Nothing.:cry:

[timsrv]

Before I found that site I was purchasing these from Toyota and was paying almost double. The only difference between these and Toyota is the box. So unless you really really care about getting the little red box that says Toyota all over it then this is the way to go. Tim

PS: The EGR modulator sits on top of the engine and is pretty easy to check. If that's okay then chances are the EGR valve is okay too. Tim

[Burntboot]

HB - My van was similarly modified. I only realized when I got the OE rear pipe, O2 bolts into the pipe just aft of the cat rear connection. I too went a/m on the O2's and cat as OE were stupid expensive.
Big improvement in fuel mileage is the pay off.

[Harbilly]

I could use the big improvement in mileage! Good to know! Thx:thmbup:

[eddieleephd]

Hey guys I did search but found nothing.
Where is the plug for the rear o2 sensor???
Usually I would just follow the wire from the old one. If it were on the van I would!

Unfortunately there is nothing behind the cat but an axle!!
So where does that plug sit?
Does it attach to anything like the transmission? That is where it is on the Tacoma "on top of the trans."
is it clipped to anything where do I look?

[Burntboot]

Ed - on the underside of the floor of the van at the back, closer to centre I think, there should be the male end of the connector, mounted in a bracket. IIRC there were 2 choices on mine, but the O2 only fit in one of them, tie up the wires so they don't get tangled up with the driveshaft.
BB

[timsrv]

The wires to that sensor should be black and black/red.

[eddieleephd]

Thanks guys,
I took the van to get a new muffler today and will get the sensor soon.
I just hope the plug is still there, no idea how the muffler came off.
The van is new to me so we'll see!

[foreverly]

Go to www.sparkplugs.com (http://www.sparkplugs.com) for the best prices on OEM sensors. For pre 88 vans with a single one wire sensor, you would want OEM identical Denso part #234-1051 for about $35.00. For the 88-89 vans with 2 sensors, the OEM identical front 4 wire sensor is Denso #234-4055 and lists for around $70.00. The rear OEM identical sensor is Denso #234-2062 and typically goes for around $100.00. This is a little weird because the front sensor is more complex than the rear (front one has a built in heater). Denso also makes universal O2 sensors that can be used. These are basically the same as the OEM identical sensors except the wire end doesn't match up to your wire harness. For those, you need to cut the wire end off your old sensor and splice it onto the new sensor. Depending on the sensor you need, you may prefer to go this way, as in some cases you will save a lot of money. For the pre 88 vans, you need universal Denso sensor part #234-1057 and they run about $30.00 (not much savings). For the 88-89 2 sensor vans, it would be universal Denso sensor #234-4050 for the front (4 wire) for about $50.00 (big savings) and universal Denso sensor #234-2050 for the back (2 wire) at around $40.00 (huge savings). Tim

sparkplugs.com is directing me towards #234-1056 for my 87 Dx which it says is an OE Identical sensor.

Should I go with 234-1051 or 234-1056? Perhaps the 1056 is an updated 1051?

[timsrv]

Go with 234-1056. I double checked and cross referenced and it appears that Denso changed that part number.

FWIW, I looked up the Toyota part number to be 89465-29195, then cross referenced it on Denso's website. I checked the old part number of 234-1051 but according to Denso that part number doesn't exist anymore. When I type that number into www.sparkplugs.com's cross reference system it still comes up as a valid part number, so if they still have those I'm pretty sure they would work too. Tim

PS: to avoid future confusion I changed my original post to reflect the current part number.

[Harbilly]

I never reported back:
Both sensors are in. A new cat is in. All went well.
I have yet to check the egr. We just welded on a mount for the rear sensor and plugged it in.

[mahleek87]

Just ordered #234-4055 for my 89 van and the grand total was only $44.93. I guess its not $70 anymore. Yay for savings! :dance2:

[timsrv]

Yeah, this is an old thread. Even older than the date here suggests (as I copy/pasted it from one of my posts over at TVP). As these things get older sometimes parts like this go down Yeah! :dance2: Of course this is off-set more & more as things become NLA & dealer parts (whatever they have left) continue to go up.

[fuquan]

Does anybody know if these sensors come with gaskets? :cnfsd:

[timsrv]

Typically not, but this is a common gasket that can be found at almost any auto parts store.

[AD2101]

Just a quick update for anyone looking to replace their O2 sensors. I recently placed an order through Amazon for Denso upstream and downstream sensors. I did OEM replacement for the upstream (Denso 234-4055) and universal replacement for the downstream (Denso 234-2050). The reason behind mix and matching OEM w/ universal was because Amazon gave me a screaming deal on the pair, $51.00 prime shipping for both, did I mention that they're (supposed to be) DENSO?!?!?!?Anyways, get the package and tear them open, the OEM upstream replacement is as advertised (albeit it the sensor itself looked slightly different) and goes right in no problem. After hours of drinking and fighting with removing the nuts for the downstream sensor, which were horribly rusted and rounded, I open up the Denso downstream sensor box, and there's a Bosch sensor in there! Feeling like I just got slapped with a trout, I immediately pull up Amazon and see the following line on their product information page:


Note: Denso partners with other manufacturers to supply the parts your car was originally built with. This product is in a Denso package, however the part may have been manufactured by an independent Denso supplier.

So, unless I really got shafted by someone at the Amazon warehouse, apparently Denso is selling other manufacturer's sensors as their own. The Bosch sensor came in a Denso box and all the numbers on the box matched up with my order. I'm sort of left in quandary because I'm honestly not sure the hassle of returning the Bosch sensor is worth it, especially since it is brand new and AFAIK, will still work. I know some people do not like to put Bosch parts on their Toyotas but I'm not sure why.

I'm not sure if this is an Amazon only thing but I wanted to put it out there so other TVT guys are aware. The Bosch sensor appears to be high quality and I really only looked into it because the sensor is distinctly different looking from the Denso ones. Reading the size 1 font etched onto the sensors was the only other giveaway.

[timsrv]

Yeah, I'm a little hesitant towards Bosch, but I don't actually have good reason to be (at least not on their o2 sensors). I got an o2 sensor code on my 86 & fuel economy went in the toilet so I swapped it out with a new Bosch universal sensor. 2 weeks later I got the same code again (not to mention I continued getting crappy gas mileage). This time I put in a Denso, but as a precaution I also ran a new wire from the sensor up to the ECU. No more codes and fuel economy instantly improved (about 40%). I know when troubleshooting you're only supposed to change one thing at a time, but I was impatient and wanted the problem gone.

So anyway, the question is "did the Denso sensor solve the problem or was it the new wire?". I guess I'll never know, but since then I've been prejudiced against the Bosch sensors. Tim

[ratatouille]

Just ordered and received o2 sensors off sparkplugs.com , for my 88 LE 4wd. Wanted to double check I ordered correctly? As the new sensors are a little smaller than the old ones pulled out. Actually I'm only comparing the upstream sensor at the moment as the rear downstream sensor nuts are rusted and rounded and i'm stuck trying to get them off.. ug.

Ordered:
Denso 234-4055 (4 wire) 41.93 & Denso 234-2062 (2-wire) $83.70.

They shipped from a Monarch Products, Inc. out of Menifee,CA. They came with the gaskets needed & they included a package of latex gloves as a "free gift".

[timsrv]

Denso sensors are smaller than Bosch, so perhaps that's what's in there now? As long as the studs line up with the holes you should be good. Tim

[ratatouille]

Going bonkers. Cursing and hacking I finally got the rusted stripped nut off the rear o2 sensor bolt.. took some work but the sensor finally came out. Go to slip the new one in and it doesn't fit. The one upstream fit fine... I'm about to just cut the rear tail pipe off I've had it :anger:...do i even need the downstream o2 sensor? ha.....

perhaps the downstream sensor mount is not original? Not sure what to do.. Maybe drill out the hole in the mount to fit new sensor? hmmmm

27242723

[AD2101]

the new sensors are a little smaller than the old ones pulled out.

That was my experience with the upstream sensor as well when comparing it to the (I assume original) one that came off of the van. I just chalked it up to minor improvements made in the past 26+ years. My new upstream is working fine and throwing no codes so I wouldn't worry about the minor changes.


Going bonkers. Cursing and hacking I finally got the rusted stripped nut off the rear o2 sensor bolt.. took some work but the sensor finally came out. Go to slip the new one in and it doesn't fit.

That sounds like me last month with the cursing and hacking :anger:. That is strange that the new sensor doesn't fit, maybe there is residual gasket material/junk on the edges of the hole that is blocking installation of the new one? I don't imagine that's the case though (worth a shot). I don't see how drilling out the hole would hurt but getting a drill to it might be hard with all the angles and where it's located.

[ratatouille]

Yeah at first I thought it might be gunked up.. but its not. It definitely does not fit. It is a little tight to get a drill in there to try and drill out the hole. Kinda stumped at this point. I may need to find a different sensor that will fit.

Upon closer inspection of the old removed ones, they are marked as Toyota sensors. Which makes me think the rear mounting is original and not modified...

[ratatouille]

Was able to drill out hole a little larger to fit the sensor. How important is it to a have a good seal between exhaust mount, gasket and sensor flange? After tightened down it looks like there is a little bit of gap between. I was afraid to tighten too much for risk of breaking the already abused mounting bolt...

[AD2101]

Was able to drill out hole a little larger to fit the sensor. How important is it to a have a good seal between exhaust mount, gasket and sensor flange? After tightened down it looks like there is a little bit of gap between. I was afraid to tighten too much for risk of breaking the already abused mounting bolt...

I would imagine that its fairly important. If there is not a good seal between all parts the van will likely sound a little worse, as its essentially an exhaust leak. Outside air getting into the area might mess with the voltage that the downstream sensor reads as well. It obviously doesn't need to be torqued down, but hopefully you can get enough on the bolts so that it makes a nice tight seal.

[ratatouille]

Thx, that was my thought. Seems to be running fine with no more code, even w/o as good of a seal as I would really like. Guess it be on my list to eventually revisit and possibly weld new mount.

[TVCamper]

I'm going through a similar saga with the nuts on oxygen sensors being rusted and rounded. The downstream sensor is definitely the worst, but both are bad enough that a socket won't fit on them and there is just not room there to get most of my tools in! What ended up working for you guys? Any tips or tricks. I don't know if all vans have these splash guard things on them but they make the whole situation pretty tight.

I (maybe stupidly) tried to cut into one of the nuts on the downstream sensor because I thought it might be rusted enough to just break open easily. It hasn't yet though. May not be using the right tool (Dremel) and can't really get to the nut from another angle with this.

Ready to go crazy so any help would be much appreciated!

649564966494

The last picture isn't an oxygen sensor obviously but something I saw while down there above the oil pan and was wondering what it was if anybody knows.

[AD2101]

I ended up cutting out that shield as I couldn't get any access either. I figured a new shield would be easy enough to fab with some scrap metal if need be, but am not running any kind of shield as I live in the southwest and it rarely rains. I suppose the shield would also block rocks and other debris, but :?:

Once I cut out the shield I had plenty of access but the nuts were all rusted to hell. It still took a few more hours of PBlaster, yelling, cursing, and a pair of vice grips before I could get the bolts free.

As for that last picture, I believe that's the rear transmission mount (see below)

6514

Thanks for pointing this out, I went out to look at mine after looking at this thread and the whole bottom half of the mount has eroded away to nothing, like I could stick my finger in it and slide it around the whole bottom half of the mount, which I'm pretty sure isn't right or safe. I'll be tackling this imminently once I finish my current project (rebuilding the drums :pissed:).

[Gambit]

Just a heads up that I also had to bore out the rear O2 sensor hole of my '88 4wd to allow the new sensor to fit (Denso #234-2062. ​Wasn't a huge deal, but it didn't plug right in.

[timsrv]

Just a heads up that I also had to bore out the rear O2 sensor hole of my '88 4wd to allow the new sensor to fit (Denso #234-2062. ​Wasn't a huge deal, but it didn't plug right in.

For anybody else doing this, Toyota used 2 different rear sensors in 1988, but now both are obsolete and cross-over to a single part number (Toyota #89465-29336). That part number is supplied to Toyota by Denso (Denso #234-2062), so if you're after OE (in my opinion the best), and don't want to pay extra for the little red box that says "Toyota" on it, then this is the one you want. It is specifically for 88 - 89 vans and will work in the rear sensor location only. And yes, on some vans you will likely need to bore out the hole a bit (I know it's a PITA). It's possible some aftermarket sensors will fit without the mod, but I couldn't say which ones and/or the quality you could expect. Tim

[rowemjr]

I never reported back:
Both sensors are in. A new cat is in. All went well.
I have yet to check the egr. We just welded on a mount for the rear sensor and plugged it in.

Is the rear mount just a universal bung modified to fit or is there actually one available that works without any modifications?

[cpginkpt]

88 4WD

replacing my catalytic and looking at Rock auto. Bosal with included O2 sensor <> Walker + add a sensor.

Any reason to go with one or the other? Also what's the deal with the O2 sensor pricing/"features" assuming I go with the Walker - why are some sensors $23 and other $70++?

Thanks.

[Burntboot]

Pre 88 vans didn't have the rear sensor, Walker makes jigsaw puzzle exhaust, so ordering the correct over axle portion (with or w/o o2) is how they got around one system fitting all years.

Bosal 2 made complete rear sections (->87MY,88MY->)
But probably not an issue as I believe the Bosal stuff is long gone, the Walker may also be in the same boat.

Rock Auto pricing can be confusing because in a lot of cases they are dealing with odd lots and cast-offs and inventory liquidations.... because of that, pricing isn't always the deciding factor (on quality) over there.

I have had really good luck with NTK and Denso sensors
On the other hand, I will never install another Bosch o2

[Burntboot]

And if for some reason you have actually found a real live Bosal exhaust, that is the way to go.

The fewer the connections, the fewer the leaks and the Bosal unit aligns nicely on the hangers.

[cpginkpt]

Thanks for the tips, so I am going Rock Auto with the Bosal Cat since they say they have it in stock...

...BUT the NTK lists both an upstream and downstream sensor.

My current setup only has 1 sensor (?) so which should i get (or both?)

[Burntboot]

Your van has 2 Oxy sensors
One up at the manifold, the other just behind the cat.
In terms of up vs down, the one after the cat is "downstream"

[cpginkpt]

awesome. Thank you!

[Flecker]

Pre 88 vans didn't have the rear sensor

I have had really good luck with NTK and Denso sensors
On the other hand, I will never install another Bosch o2


I will second the Denso O2 sensor. Direct fit and quality product... for O2 sensors I only ever used the Toyota/ Denso application and has always worked flawlessly.

Question On the later vans with two O2 sensors... are they run in tandum, or does the ECU get two signals to it?

[cpginkpt]

Interestingly the Bosal cat actually says “w/O2 sensor” in description.

Guess I need to clarify that with Rock before I order the Denso O2...hmmm

[JDM VANMAN]

Here’s the downstream sensor out of a 4WD auto-



http://i.imgur.com/rgEhojt.jpg
http://i.imgur.com/k1FiOkF.jpg
http://i.imgur.com/RP2hvVJ.jpg


JDM

[Burntboot]

Flec - Question On the later vans with two O2 sensors... are they run in tandum, or does the ECU get two signals to it?

Code 27 - sub-oxygen sensor signal, open or shorted

[HI_Beach_Van]

My July 1989 van is showing the 21 code. the PDF from another thread ( https://www.toyotavantech.com/forum/content.php?195-Diagnostic-Codes-for-Toyota-Vanwagons-all-years ) shows it as either the Upstream or the downstream. How do I determine which sensor needs replacing?..I would prefer not to have to change them both out unless it is necesary.


https://youtu.be/BPizY-OJslU

Thanks for the help!

[llamavan]

The upstream sensor by far gets the most abuse (heat, carbon), so replace that first, clear the code and drive.

Gwen

[iq_artwork]

Hello everyone,

I ran my codes today and I got the code #5 (oxygen sensor signal). So I'm planing to replace it in my van.
I have heard and read some vans have 2 sensors and some ones one senor. I'm guessing my old generation '84 van has one sensor.

https://www.youtube.com/watch?v=8UNkX1RSUDo

I found via this website, Tim shared here this denso sensor. Is this the right part?

https://www.sparkplugs.com/product.aspx?zpid=17828

Thank you!

[timsrv]

Yes, that one should do the job.

[iq_artwork]

Thank you Tim for your reply! I have ordered the sensor and it's on the way.

Today I checked under my Van and I noticed my 02 sensor is broken and looks like always was broken. But I have never had a check light on and off when i was driving.

A month ago, I cleaned my Throttle Body, replaced and adjusted a new TPS, replaced all my vacuum hoses and my mechanic replaced the fuel injectors.
I noticed the van is ruining way better, faster and smoother.

So I was wondering if all these changes have to do with it?

10485
10486

[timsrv]

Every little bit helps. The van ECU has a "default" mode that it goes into when it can't see data from sensors. Because running too lean can damage the engine, the default mode makes it run rich. Rich running engines get poor fuel economy, run dirty and do not perform well. If left to run rich too long, other bad things happen like plugged up cat converters and fowled spark plugs. By repairing/replacing you are giving the ECU back the basic tools it needs to do it's job correctly. I suspect you will notice a MAJOR improvement in power and fuel economy when you get a good o2 sensor in there. Tim

[iq_artwork]

Amazing! Thanks again Tim! :thmbup:

[LGW]

I have a 1991 Townace (YR30 5013276) 3y engine. The original oxygen sensor number is #89465-19066. Does anyone know a comparable sensor I can use?