I just finish checking my mother's 740 gl/135k and the dreaded check engine light saids code 212 oxygen sensor. I would like to know if a can replace it with a cheap sensor that would require splicing up the wires. Would this work? I also would like to know of a cheap source for this sensor. I am also open for ideas or suquestions. Thanks for any help in advance.

HF

Last week, I found prices ranging from around $200.00 (IPD, Dealer) to $112.00 (Autozone). All for precisely the same Bosch part on my 240. No splicing weirdness - it was the original part. Its likely the same situation for your 700. Figure out the Bosch number and go from there.

Try IPS at 1-800-897-7278. The universal three wire sensor is cheap but will require splicing. The two dark wires are just for the O2 sensor heater, not critical connections. The white wire is the O2 sensor output. It runs just under on volt output. Solder this connection for better long term reliabilty of the electrical splice, but crimp fittings on the other two black wires are fine.

Just a comment:

"The white wire is the O2 sensor output. It runs under one volt output. Solder this connection for better long term reliability of the electrical splice, but crimp fittings on the other two black wires are fine."

Actually, when crimped with a proper crimp tool and weather-sealed correctly a crimped connection is more reliable that a soldered one. I know this smacks in the face of convertional logic, but here are the two primary reasons:

1. Under exterme temperature conditions, a soldered connection will come unsoldered. I realize this is an unlikely scenario, but the O2 sensor is in close proximity to the exhaust manifold. And I guarantee that the manifold gets hot enough to melt solder.

2. The process of soldering wires together actually causes the wires to work-harden. After a period of time of sustaining random vibrations, it will break. again, I realize that this period of time may be quite a while, but it will happen.

Remember, commercial airliner wiring is always done by crimping. And it isn't because the mechanics don't know how to solder!

But the key here is to use a PROPER crimp tool, and appropriate crimps. Don't grab a couple spade terminals and mash them with a pair of pliers. And also remember to weather-proof the splice with some kinda goo that will withstand reasonablly high temperatures (again, reference the exhaust manifold).

Thanks for the lecture. I am well aware of the merits of pressure connectors. I should have stated my case a little better. All I ever make at work (over 20 years in the electrical industry) are mechanical crimp fittings. Soldered connections will not conduct power very well for very long. No tool is used for crimping unless it is UL listed for the crimp fitting being used in the business I am in. I am also quite familiar with aircraft avionics. The highest start of the art, for electrical fittings on aircraft is a fitting which is crimped, and then soldered to keep moisture and possible corrosion out of the fitting. Beechcraft Aircraft use crimped and soldered electrical fittings. Beechcraft is considered by many to be the best manufactured small aircraft. I don't bother with the soldering on avionics. The low voltage output of the O2 sensor is susceptable to losses at the electrical fittings. Crimping is my preference, but for locations with all the moisture that can splash into an engine compartment, the crimped fitting for the O2 sensor needs to be soldered or sealed against moisture, as you stated. As far as crimped electrical fittings are considered I have encountered a bad fitting on the alternator field connection of a Cessna 172. The factory fitting was intact, appeared good, and would check for continuity with my Fluke meter. However the fitting would not conduct enough current to operate the alternator. Replacing the crimp fitting restored the alternator to operation. I have also had the identical experience on a car. Would you car to explain the work hardening? If you heat copper to cherry red and air cool it, it becomes hardened. I don't think soldering reaches that temperature to harden the copper. If the copper wire breaks off near a solder joint, it is probably because the solder has made the joint ridgid, and the flexing of the wire occurs where the solder ends. The copper will stress and crack there. Yes, if you make the splice with solder, it needs to be in a location that does not flex.

No, thank YOU for the lecture.

You're right, my semantics were wrong when I said that soldering work-hardened the wires. Clearly what I was referring to was the flexing of the wires at the point where they are soldered.

I'm not sure I agree with your statement, "The highest state of the art, for electrical fittings on aircraft is a fitting which is crimped, and then soldered to keep moisture and possible corrosion out of the fitting." Even IDG feeder wires on aircraft such as a B767-200 or -300 aren't soldered. In fact, Boeing allows for three splices on one of these wires (keep in mind it is delivering up to 90KVA at 115VAC).

I certainly DO agree with your comment, "The low voltage output of the O2 sensor susceptable to losses at the electrical fittings." I realize the implied message is to use as few "connections" as possible (a "connection" being any mechanical discontinuity in a wire, compensated for by crimp, solder, or terminals).

BTW, what aspect of electrical industry are you in?

Hi I tried a splice job on a 86 240 and it didn't work. The car wouldn't pass smog. Maybe I got a bad O2 sensor. My Volvo mechanic said that the splice sometimes causes problems with the resistance reading the comp makes. Replaced the sensor with a factory one and the car ran better then before and passed smog. Also got better fuel economy.

Humberto..

There is nothing special about the volvo o2 sensor. You can just go to your local autozone, pepboys etc.. and get the cheapest 3 wire bosch they have.

check the faq as well, there may be some part numbers and prices..

Brendan

'90 745t m46

Humberto,

I don't know how much the factory Volvo O2 sensor would be but I just put in a single wire (unheated) O2 sensor in my 1984 Pontiac Firebird. It was $29.95 with tax and came with the correct connector. The three wire sensor for a 1994 Volvo 940 Turbo can be ordered from Advantage Auto Parts for $192. I'm sure yours would be comparable if it is a three wire.

I haven't checked about the factory Volvo part but hopefully they haven't decided to use a "special" sensor at a "special" price.

Greg

I did this recently for my 1991 940 Turbo, and NAPA wanted $160. Dealer wanted over $200 (whadda ya expect???). Found a local import place (BAP-Geon) in Richmond, VA that sold me a Bosch three-wire job for $120 (same part #, no splicing, straight R & R).

Look around, and chances are you can save a few bucks (like $40 to $60+).