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Old 04-06-2002, 11:59 AM   #1
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Question Are the front and rear oxygen sensors the same?

I need to buy a pair of rear 02 sensors today and I was told before that the front and rears were the same. Is this true? I think it may be because every place I go to buy them they only show for the front bank and not the rear. Anyone Know for sure?

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Old 04-06-2002, 12:02 PM   #2
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I believe the are in fact the same sensor and only differ in keying. If you go to oxygensensor.com they also only list one senor for the car. I think the Ford unique part number only calls out the different keying. I'm doing a little research now to see if indeed this is true...
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Old 04-06-2002, 12:50 PM   #3
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I'm fairly sure they're different parts. If there the same part, why would Ford bother with the different part numbers and keying?

When i replaced my rear (downstream) sensor, i saw a chart which said the front (upstream) sensors were O2 sensors for engine calibration and the rear sensors were for emissions monitoring.

What backs this up- i toasted a cat in my Bassani x-pipe (supprise) and got an MIL. I accidently got the wrong part, but i was under the car by the time I figured it out, so i broke the key tabs off and plugged it in. Guess what- no cat AND no MIL. I'm guessing the front sensors are calibrated for a "raw" exhaust stream so when you put a front sensor in the rear without a cat it still shows as in compliance. ?? I donno, but it did work..
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Old 04-07-2002, 01:17 AM   #4
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Quote:
Originally posted by 99SoCaCobra
I'm fairly sure they're different parts. If there the same part, why would Ford bother with the different part numbers and keying?

When i replaced my rear (downstream) sensor, i saw a chart which said the front (upstream) sensors were O2 sensors for engine calibration and the rear sensors were for emissions monitoring.

What backs this up- i toasted a cat in my Bassani x-pipe (supprise) and got an MIL. I accidently got the wrong part, but i was under the car by the time I figured it out, so i broke the key tabs off and plugged it in. Guess what- no cat AND no MIL. I'm guessing the front sensors are calibrated for a "raw" exhaust stream so when you put a front sensor in the rear without a cat it still shows as in compliance. ?? I donno, but it did work..
Since they have a different connector on them with different keying I think from a stocking standpoint Ford has no option but to have different part numbers. They are unique assemblies due to the different connectors. And I think Ford bothers with different part numbers and keying to prevent maintenance errors when working on the exhaust. A particular O2 sensor goes in one of the four locations in the pipe and it has unique keying in the harness to prevent any assembly errors. In fact I work in military electronics and this is mandatory from a maintenance standpoint on electrical assemblies. If two connectors will physically mate together then use unique keying to prevent mislocation of electrical assemblies.

And yes the front O2's are for tuning and the rears are for emissions only, but that doesnt mean they arent set for a lambda of 1.

Again, I'm still looking into it but I still believe the sensors themselves are electrically the same...
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Old 04-07-2002, 10:07 AM   #5
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WELL...

...the rear sensors are O2 monitors and have nothing to do with fuel adj by the ECM. dont mix them up(seen people cutting off the locating tabs to make work, dont do it) aftermarket sells O2 sensors but not the monitors, you have to get them from FoMoCo.
have the monitors in stock and the Bosch/Motorcraft O2's in stock in several wire lenths for you guys with long tubes.
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Old 04-07-2002, 12:19 PM   #6
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Jesus Christ, I give up... Like I said, I'm looking into it. I get asked this quesiton a lot so I want to know also. If they are truly different, then I'll start saying that. But just because Ford calls the rears "O2 monitors" they dont magically transform into something else. I've looked at both sensors on an NGS port monitor. All trouble codes refer to them as oxygen sensors. I'm sure they are oxygen sensors, and narrow band oxygen sensors just like the front (remember then scan tool...). If they differ in ANY way it will be the lambda. And if they differ in THAT way the sensor itself will have a different part number stamped on it PERIOD. If the number is the same, they ARE the same sensor and function in exactly the same manner.
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Old 04-07-2002, 12:31 PM   #7
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I put on my Pro Chamber and had to replace both the front and rear drivers side o2's. I repaced them with Bosh from Auto Zone and the part # is exactly the same 13127. The have it listed in there computer that they ask for driver or passenger rears, but the number is still the same for both. The plugs on our cars are just different colors, but the plugs are the same. I think that is why Ford uses different part #'s because the plugs are different colors. I have no problems with my Bosh sensors and they were only 64.99 each instead of 100.00 at the dealer. Hope this answers your question.

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Old 04-07-2002, 12:42 PM   #8
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they r different.

...check the stamp #"s. O2 use the "basic" part # 9F472 and the monitors use the "basic" part # 9G444. yes they both scan but
they scan for different reasons. so dont mix them. period !
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Old 04-07-2002, 01:21 PM   #9
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And Randy, the numbers you just listed are the Ford part numbers. Not the O2 sensor manufacturer part numbers. 9F472 and 9G444 look exactly like most other Ford numbers. As Orange Peel pointed out the Bosche number is actually different. I'll bet Ford uses Bosche sensors. I dont know if the OEM parts will have the Bosche number on them, but maybe. See if you have that stamp on them.

Also... one more time.... When we we're developing the MIL Eliminators I looked at the front and rear O2's on an NGS. Without cats the signal looked the exact same on the fronts and rears. Which means they were toggling around the same point, the stoichiometric point of 14.7:1 A/F ratio which corresponds to a Lambda of 1.0. If indeed the sensors had different Lambdas, then the rears would have had a different duty cycle on their waveform. They didnt, they looked exactly like the front. Therefore they are the same sensor...

Plus as Orange Peel stated having the same sensor in the front and rear works just fine... And other people have observed this also.

[edit] I went to Bosch's web site and poked around. Here's what I found...



LSF 4
Application
- Gasoline engines (Lambda =1)

Advantages
- Fast light-off (<10s)>
- Wide operating-temperaturerange
- Stable control characteristic
- Improved exhaust gas values
- Low power consumption (7 watt)
- Isolated ground
- Small size
- Service life > 160000km
- Super fast light-off available
(<5 s)>


This is the ONLY sensor they list for engines like ours and it is LAMBDA=1.0 They list another type for gasoline direct injection engines and has a different monitoring scheme, but this is the ONLY narrow band sensor they show for engines like ours... heres the link...

http://www.boschusa.com/AutoOrigEqui...xhaustSensors/

NOW I'm done with this...

Last edited by TriBlkCobra; 04-07-2002 at 02:02 PM.
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Old 04-07-2002, 05:30 PM   #10
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I also did some searching on the Bosch replacment part numbers. The site lists the following replacement "ASSEMBLIES"

OE Type with connector before catalyst: 13127 (note 37)

OE Type with connector after catalyst: 13137 (note 46) and 13129 (note 47)

Note 37: Two required
Note 46: Right Side
Note 47: Left Side

So... they call out the same ASSEMBLY part number for the front O2 sensors. They callout a different ASSEMBLY part number for each side of the rear O2 sensors. Would anyone care to place a money bet on whether the rear O2 sensors use the same LSF 4 sensor as the front O2 sensors and only differ in connector? Anyone? Bueller?

Oh and also, I know that if you swap the rear O2 sensors in the harness it will throw a MIL. Could that be why they have different assembly part numbers with either different color/keying connectors?

[edit] I'm not even going to bother saying I'm done with it And Randy, this is not personal. I just have a different opinion thats all. If one of us can't convince the other then lets just agree to disagree, but there's a lot more important stuff to get bent out of shape over than this stuff

Last edited by TriBlkCobra; 04-07-2002 at 05:41 PM.
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Old 04-07-2002, 06:44 PM   #11
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All O2 sensors WORK the same. They have paladium which reacts with the exhaust. (Only the widebands are different.)
People with mercedes and Jags adapt ford O2s because they're way cheaper. They screw in and work the same.
If you really need to, you can unlock the pins in the connector and use your old one. They have a tiny catch holding them in.
If its true that they pop a code, then there must be something in the wiring like a resistor. All O2s work the same.
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Old 04-07-2002, 06:51 PM   #12
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terryr, I know and I agree. The comment on the MIL was if you swapped the sensors side to side in the pipe. IE hook the drivers side rear O2 into the passengers side harness port. I was trying to point out thats why I believe there are two different Bosch part numbers for the rear O2 sensors, thats all.
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