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?)

[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 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.

[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

[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 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?