Trying to track down a lean running condition so in the process of upgrading some obvious problem areas I just replaced the engine harness in my 84 242 with 2.0 LH.

I didn't notice it before but my car has a 3 wire O2 sensor and the harness has a 2-pole connector to accommodate the heater.

I have a single wire Bosch 11032 O2 sensor from another car I owned with LH II. (also 84)

Both types are listed by suppliers for this car. Why? Is one better than the other? One more trouble?

"Both types are listed by suppliers for this car. Why?"

In 1984, a late production change added the heated oxygen sensor and harness to power it. I believe the model year is sometimes referred to as 1984.7 -- something like that. It is an improvement both to function and longevity, so take advantage and replace the sensor with the same type, the three-wire sort.

All replacement harnesses for the LH2.0 harness include this improvement.
--
Art Benstein near Baltimore

"Freedom is not worth having if it does not include the freedom to make mistakes."
-Mahatma Gandhi

These guys are a good source for O2 sensors, including the OE plug-n-play Bosch unit for your LH system:

www.stockwiseauto.com

--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

Would you know the part number for the correct 3 wire Bosch part?

Not interested in aftermarket.

The only three wire Bosch I saw for a 240 is P/N 13597.

https://www.stockwiseauto.com/bosch-13957-oxygen-sensor?Year=1985&Make=Volvo&Model=244

That supplier says it fits 1985-up. No three wire sensor listed for 1984. But from what Art is saying, the three wire wasn't incorporated until late 1984, so it's possible there just aren't many, if any, 1984's using that configuration.

Looks like they run the pre-heat wires through a separate plug. Does yours look like the picture?
--
Current rides: 2005 Volvo S80 2.5T, 2003 Volvo V70 2.4NA, 1973 Volvo 1800ES (getting ever closer to road worthiness)

That is the one. Volvo part number is 1346738 unless it has been superseded. It would be for LH2.0 with heated sensor and all LH2.2 Volvos.

Some vendors depict the single wire sensor where they list this part but it really is the three wire heated sensor as shown in the picture to which you have provided the link.


--
'80 DL 2 door, '89 DL Wagon, '15 XC70 T6

Thank you all. Can't open the link but the part number provides visual verification.
-Dan

Having a frustrating time with this one. Car has a very recent AMM which statically tests good. (also engine "hunts" when running with the AMM disconnected like it should) Although it tests good with an ohmmeter I can't get a reading from the pink test wire with a dwell meter.

I put in a new engine harness from Dave Barton. The original was badly frayed and very poorly patched together. No vacuum leaks, starts right up with active relays even though I haven't checked fuel pressure.
Fairly smooth running except you can't accelerate without hesitation and popping.

Got a used ECU from a friend of mine that didn't work. (wouldn't fire the relays) Just received a remanufactured ECU (510) from Programa with which the car won't start. That got me really worried until I saw that the blade connector for pin # 25 is broken off. (ground for TPS, O2 and ground ring)

Just sent them an email about it and asking how quickly they can get me another.

Hi,

The heater built into the sensor is for quicker signal making, since the sensor has to warmup.
The quicker signal makes the fuel management system go closed loop quicker by a half minute or so than one with no heater.
You ask? One is not better than the other just one has a "cheap to make" ceramic encased coil of ni-chrome wire. If it cost more than five bucks I would be surprised.

As far as I know the heater was not required until LH 2.2 or about 1985-86.
Even then there is no need for it except for above and since do not have a check engine light it will not need it for smog.
The heater is not monitored until the LH 2.4 or 3.0, if even then? I'm guessing, if a light/code comes on for that sensor it is probably more for a no signal reason than the heater.
I doubt the ECU program even has a set time limit to see that signal but might need it, after the computer knows the engine is up to operating temperature, from the ECT sensor.

I just save my money and use a single wire universal.
You can get heated sensors for less money if you splice in another brand like from Ford.
They had to provide their customers with a more afFORDable ones as some of their cars went crazy and used up to ten sensors on one vehicle.
Maybe not all were O2 sensors but a bunch before and after the converters per side.
I think(?), it was the Crown Victoria and maybe the Navigator, that are no longer made, used that many.

Maybe many other wiser posters, can correct my statements, as most of what I said is an opinion from my own experiences.

Phil

Well, I got a replacement remanufactured ECU from Programa. The car ran sightly better but still would not accept fuel with throttle and would pop/cough on acceleration indicating a lean condition.

Today I finally checked the obvious, the O2 sensor. The "heater" checked OK on the ohmmeter but the sensor itself had a fixed voltage reading when running. Not fluctuating as it should. No change when inducing a vacuum leak like opening the oil filler cap either.

It was stuck in the condition of response to a too rich mixture and so the ECU was maintaining the lean condition.

I plugged in the used single wire 11032 unit I had sitting on the shelf and instantly the car ran as it should. Fluctuating voltage and now I had to turn down the idle, always a good sign that a car is running better.

Tons of smooth power delivery. (for a Volvo 240)

Will order another O2 sensor and will take advantage of this later LH2.0 build and get the 3 wire version.

Don't throw away old parts known to be good!!!