My check engine light has been on, and I just found the fault codes (thanks to the help of many of you on this site), and it is most likely that I need to change the sensor(s). To my understanding there is an upstream and downstream sensor.

My car runs well, no hesitations, no startup issues, and no noticable loss of gas mileage. Do I need to change both sensors, or should I just do it anyway (ie. is one more likely to be the culprit)?

I am inclined, with 98k on the car, to just replace them both, is this a smart move?

Finally, I have been looking for sensors and noticed that I can get universal sensors for up to less than 2/3 the price of OEM. The universals require splicing, etc... Should I go with OEM fits, or will the universals do the same job? Also, I noticed brands like Bosch have both universal and OEM, which makes me wonder if the only difference is the "exact fitting" vs. splicing fits. So, if I get a universal, will it do the same job as the OEM, as long as it's installed correctly?

Thank you.

Again, you are using info for a 210 E320 w/OBD2 instead of a 124 chassis E320.
Your car is a 124.032 w/OBD1 and it does not have downstream sensors..it has one 4 wire sensor.
And looking at your codes . I would check the 12v to the sensors heater and the heaters coil before doing anything b/c that is what your codes indicate.

You have a 1995 E320-124 chassis. Here is what you have:

http://catalog.peachparts.com/ShopByVehicle.epc?q=1995-Mb-E--3--0--Sedan-Fuel--Injection&yearid=1995%40%401995&makeid=MB%40%40MB%40%40X&modelid=E%2D320%2D001%40%40E+320+Sedan&catid=C%40%40Fuel+Injection&subcatid=C5010@@Oxygen+Sensor&mode=PA

Here is the sensors for a 1996 E320. That is a different chassis , even tho it is still a E320. Notice it is not a 124 chassis, but a 210.
Always mention your chassis when asking questions on E320 [ or year] b/c they are very different in many ways. Like 02 sesnsors.

http://catalog.peachparts.com/ShopByVehicle.epc?q=1996-Mb-E--3--0--Sedan-Fuel--Injection&yearid=1996%40%401996&makeid=MB%40%40MB%40%40X&modelid=E%2D320%2D002%40%40E+320+Sedan

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A Dalton

Not sure what Arthur thinks but Doc once wrote that Bosch universals are fine for OBDI cars. You just have to check the price of both and see if it's worth it to you. It's located on the top of the exhaust pipe pretty much right underneath the console with the wiring going into the passenger footwell / 22 mm open end wrench.

Mr. Dalton, I have read a lot of you on this site already, so I'm a little intimidated to ask you, "are you sure?"

I have a 1995 e320 Sedan. My understanding is that it is a 124, and the codes I used are from another Thread, saying #2 is the Heated Oxygen Sensor, #4 Air Injection System faulty hot film mass air flow sensor with hot wire, and #26 Upshift Delay Faulty.

This was read off a 16-code box (indicates 124?) with the reset and little light, by pins 2 and 4 (if I recall correctly) right by my battery, as you told me in an earlier response. I cycled this 3 times to be sure my reading was correct, and each time it was 2, 4, then 26.

So, when I look up the part on-line and calling parts stores, both indicate that there is an upstream and downstream sensor? Some even said, front and back.

I am a genius when it comes to computers, but a complete moron when it comes to this stuff, I think I know how you feel, so I appreciate your patience with me.

>

No..I am just guessing........

Have you read any of my tutorials and postings on 124.032/124 chassis HFM/SFI Engine Maagement Sytem Dagnostics ??????

Are you aware of the inter-ralationship of an O2 sesnsor code 2 and a code 4 AIR system code on a 124.032 chassis ????
A very common diagnostic combo, I may add...............

Your code 26 is upshift delay and another common HFM/SFI code.

Let me assure you I am SURE ...........

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A Dalton

I remember once when Arthur made a mistake, so theoretically it could happen again.

The jury is still out on Uni sensors....but the Bosch replacement seem to be OK.
.........here is the rub with the UNI sensors when used on the 124.032 HFM/SFI sytems [ The posters chassis , by the way]..

When one gets an 02 sensor code COUPLED with an AIR code on this system, [ the posters condition, by the way] , it indicates that the 02 sensor is no longer capable of attaining the extra lean [ low voltage ] readings required by the ECU self test for the AIR sustem. The AIR system uses the 02 signal to monitor the working of the AIR system. The ECU sends a self test signal to the AIR system when the cars coolant temp is up and it then looks at the 02 sig to see if the exhaust goes extra LEAN. If the report does not come back as such, then the DM [ led/sw N59 module ] brings on a code to notify the driver by popping the CE lamp and an AIR code #4. . So, is the AIR sustem not coming On and operating as it should ??? ..OR ..is the 02 not detetcting the extra lean condition cause by the AIR system activation..???
Now , if the other code is 2 , then we have a suspect 02 sensor heater circuit, which will not only pop an 02 code, but it will be coupled with an AIR code , even tho there is nothing wrong with the AIR system.
So. those who know these sysytems start their diagnosis with the LONE 02 sensor of this system by checking both the heater circuit of the sensor and the V readings of the sensor.

The problem w/uni sensors is many are not capable of the extra low readings required to monitor the AIR system and some will still bring On an AIR code right our of the box.

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A Dalton

For sure ..

But I am confident in my understandings of the mentioned chassis and how many sensors a 1995 E320 /124.032 HFM/SFI chassis has .................

..and I went to the extra trouble to post and list all that info/site /part # search/etc. for those who doubt it.
Go back and reread post # 2, where I direct all to the sensor info for BOTH the posters 124 chassis and the included 210 chassis dual sensor page.... just so we are perfectly clear on the differences of the two chassis 02 sensor/s arrangement. OBD1 [ 124/E320] used one 02 b/c they did not monitor after the CAT. That is main function of the second downstream sensor of OBD2 systems . [ 210/E320]

If one doubts a posters answer, just go to the Archieves... The info is all in there for confirmation and comparison ..some correct , some not. ... and the parts are available at the top of the page
My informational explaination of the common mistake made by newbies on the two chassis has been explained. The E320 has always created confusion on many postings [ as we all know] , so that is the main point of both this and my other response to his other posting. 124 and 210 are NOT the same car. They are just both E320 designations.
Anyone posting for E320 info here will be far ahead to mention which one they have if they want a correct response.
When we commonly respond to such a post with "year/model" , it is not a smart-ass response ..it is a mandatory question before we can give out any correct info b/c we know the differences...unless we just assume/guess which chassis..which I have learned not to do..........if there were not as many differences in the two chassis, it would not be of importance to the diagnostics...but there is a difference. So , a simple year or chassis would and will do just fine.............
Done.

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A Dalton

You may want to check the sensor plug and connections before changing that sensor.

Under the passengers rug is the 02 Sensor connector plugs.. [ 2 of them...a single wire and a 3 wire..side by side...total of 4 wires]
This is a 4 wire/single sensor [ two wires for the sensor output to the ECU , and two 12v supply wires for the sensors heater circuit.]
One plug has 3 wires .. This is Connector G3/2x1 on the wiring schematic for your chassis. [ which shows single sensor only] ...the terminal numbers on that plug are 1/2/3... with 1 and 2 being the heater circuit, and # 3 being the ground for the 02 signal. Then there is a single plug [ green wire ]..that is the 02 Sig wire for the sig to the ECU.
[ anyone following this with Factory CD, this is engine wiring schematic 07-2.00/1-93/95 HFM/SFI W/104. Page 1....note single sensor G3/2]
You want to check that both these connectors are fully plugged in and the wires are not worn from passenger traffic, etc. If all looks good there , here is the heater circuit test procedure:
I would unplug the 3 wire connector and check across the 1 and 2 wires going to the 02 [ tru the floor] with an ohm meter...that will tell you if the heater is faulty/open on the 02 sensor ...that is a highly probable b/c of the code and a bad heater would also pop an AIR code b/c the sensor does not retain enough heat w/o the heater circuit to attain the max lean reading the ECU is looking for with the AIR activation self test. Heater amp draw spec is 1.2-2.2 amps. That equates to approx. 6-10 ohms.
If this is something you are not comfortable with, print it and give it to your mechanic, [ in the event he is not familiar w/this system].
If the heater ohms out as OK/Good, then you can turn the key ON and see if you have 12v at the feed side of the connector [ same 1 and 2 ] going to the heater in the 02 sensor. * Polarity Note --- terminal 1 is +pos.12v and 2 is -neg. 12v. That is the complete heater circuit test for 02.
If no ohms or incorrect ohms on heater, change the 02 .
An actual 02 sensor closed loop sig test for ECU can be gotten from the green/single wire connector. He will know that.

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A Dalton

Mr. Dalton is the expert here but I'll share my experience.

1995 E320, 104992 motor:
I spliced in a universal type O2 sensor. (Bosch part number 15718) Installed about a year ago, no CEL issues. Before using this sensor, I had a discussion with a tech rep from Bosch. He said that there was no difference in the O2 sensing function of the OEM part vs the universal, but that there are sometimes differences in the heating element current draw. He said that on newer cars the difference in heating current draw between an OEM and universal could sometimes trip a CEL. For what its worth, the MB sensor that I replaced was made by Bosch but had an MB part number. MB part number was 000 540 3817. There were also a bunch of Bosch numbers--I wish now that I had tried to cross reference these with the Bosch rep..... The Bosch numbers were LSH 6 12 V 0 258 003 314/315 470241

J. M. van Swaay

Gunth...
That reminds me of the line in " My Cousin, Vinnie "

He ask the witness ...........
"....are you sure ?????? " ...

...and she says..... " yeah, I'm sure !!! "

"Would you care to explain ??? " ..... "watch this, your Honor "....

Funny flick...and a good job done by Herman Munster/Fred Gwynne...

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A Dalton

I am really impressed at the speed of the response and all the information all of you have provided here. This is really great!

Um, I noticed something after I did all the resetting and code checking, when I first started my car, it seemed a little rough on idle, and it was also ticking. Is stopped the car right away, lifted the hood, checked the oil, then started up again. It didn't do anything like that before I discovered how to read the codes today. But, since then, the car has started up with all the pep that I only know of it. Did the resets have some temporary effect that caused it to auto or self-adjust back to normal from the reset? It's running normal every since the rest of the day now.

I acquired the car at about 80k, so wouldn't it just be a good idea for me to change the O2 sensor either way?

If you think that would make you feel better , go ahead.
But your first post mentions your concern of cost.
So, I would at least check the connector under the rug .. I am probably the last guy on this Forum that would recommend changing a part w/o testing it first...I have seen too many " Well, that didn't work, but I guess I needed it anyway" threads.
But there are those who will tell you to just change it....cuz they just wear out... or the code says so....don't make the mistake of what the codes mean...an 02 code does not mean you need an 02 sensor any more than an AIR code means you need an Air Pump...the codes are finding faults in the system that the part is only part of..it could be as simple as a broken wire under the rug. I also explained to you on your other post about the other codes using a homemade tool . If you go get the codes from pin #8 , then you will have a better diagnosis b/c those codes are more 02 specific.
Personally, I never change a part until I test it, specially something that is as simple to test as an 02 sensor.
You have a heater code and I told you how to address it. I tried to keep my answer as DIYer as possible , while still being technically correct
.. you ask a tech question and I have to give you a tech answer.
Will a new 02 solve the problem. ???? ..maybe ...your call. I do realise that it is sometimes a hard thing for an owner to come to a reasoned diagnosis w/o the tools and know-how, so a part change can look like a good alternative, but it is a crap shoot. [ called Shot Gun diagnostics in the trade]
I would test it first , or have your guy test it now that you have gotten the codes.
On your shift delay code 26..that is a simple and common one and I have tutorials on that in the Archieves...or one of the guys here will explain it.

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A Dalton

I have to add: If you change parts, without first knowing if they're bad, you're introducing an additional variable into your diagnostic (old vs new). In pure diagnostic routines, this is exactly the opposite of what you want to do, you want to isolate the symptoms with the least number of variables. Test first, replace later. Typically more economical also.

Second, in the diesel forum where I usually dwell, we all put our cars' year and model in our sig lines. This helps readers to understand what cars we have direct experience in, and also helps readers to see what year/model we might be discussing without having to scan back to the OP each time (especially in long threads). Just a suggestion which probably belongs in a different thread, ...

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Gone to the dark side

- Jeff

Thanks for that info, you can see that my car info is there now!