I have a 85 380SE and need to reset the oxygen sense light. It didn't have a bulb in it when I bought it so I put one in and now need to reset it. Or is something maybe broken and that's why the bulb was removed? Thanks.

The reason there was no bulb was because it was removed during the first 30,000 mile service per shop manual. Federal law at the time required that the owner be signaled and the oxygen sensor be replaced at 30,000 miles. Once this was done the workshop manual instructs the mechanic to remove the bulb. So just take it back out unless you have become attached to the glow or are looking for a conversation starter when you have passengers.

Peter

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Auto Zentral Ltd.

Thanks for the info. So how do you know when to replace the oxy sensor? Jim

The oxy sensor funtion should be checked during the regular service, when you bring your car in for service. The mechanic will check to see if it is sweeping at mid scale.

Peter

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Auto Zentral Ltd.

Does the CE light on the later kjet cars serve the exact same purpose as the O2 idiot light on the earlier cars? I know there is one fuse (for backuplights, ACC and maybe something else) that will turn the light on if it blows.

Thanks.

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

When you ask about the CE on later cars, I'm assuming you are asking about the 90 300SE you have listed. As I tried to point out the O2 light on the earlier cars was just a signal tripped by the odometer and had no fuction as an indicator of a problem. The CE on your 300 is turned on by the computer that is tucked away by the passengers right foot. What turns this light on depends on whether your car is a Calif. car or a 49 states car. Since you live in Maryland, I'm assuming you have a 49 state car in which case the light is only turned on by a malfunction of the O2 sensor. If you have a Calif. car, any # of problems in the engine compartment will set a code in the computer and turn the light on. Many of these codes will put the car into limp mode. The only way you will know if a 49 state car is in limp mode is during cold starts. The car will start and die several times and run real bad for awhile during warmup.


Peter

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Auto Zentral Ltd.

Ahh, I should have read your post more carefully. The function of the light is clear to me now.

Is limp mode the same as fixed op. mode?

Thanks for sharing your knowledge.

Mike

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'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

Mike,

You are absolutely correct. FOM is the acronym for fixed operating mode. Thanks for the appreciation of sharing knowledge. I spend alot of time helping people people here and most of the time no one ever bothers to make one more little post to say thanks. Once their problem is solved they could care less until they have another problem. Quite frankly that is the reason many professionals don't bother to help.

I am very familiar with your car. I can even tell you how to pull codes from your MAS control unit without using a Mercedes breakout box should the need arise. Glad to help. Just ask.

Peter

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Auto Zentral Ltd.

You own a 300SEL if I recall correctly? How do you like yours? Is the fault detecting capability of a CA car valuable in your opinion?




I think the "core" mercedesshop crowd is appreciative to the professionals, but yes, I have noticed that often advice goes unanswered/thanked. Perhaps the nature of the internet as everyone is 'just a screename'?

Again, thats for sharing.

Mike

__________________
'90 300SE 298k
-300K and it gets put into retirement.
'80 300D 255k Purchased new by family in 1980.

Had a:
1973 220 (gas)
1980 300SD
1992 400E

Mike,

You are correct. I presently have two of them. I have an 88 300SEL and a 90 300SEL. One MB is the same as the next to me after having worked on and owned so many over the years. These 300s seem like pretty nice cars and fairly snappy in performance considering the weight. I can't tell you about the Calif version, because oddly enough both of mine are 49 state cars. A Calif. car would make trouble code extraction easy, because you just push a little button and count the blinks. I kept getting two codes on the 90. TN signal incorrect and oxygen sensor shorted. After carefully checking the system using the official MB diagnostic manuals, I had to replace the MAS unit and the main computer to clear the codes. There was nothing wrong with the system but the faulty units were keeping the system in FOM.

Peter

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Auto Zentral Ltd.

Hey Peter,

Thanks for triggering that thought in my brain! My M103 *is* a Kalifornia model. I didn't think about reprocussions in the electronics. It did seem strange that even the engine temp sensor was different....
I've got to spend some more time in the MB cd and figure out the systems. It runs well, and starts probably in the top 20%- but barely made emissions this last year. Need to check EGR system to make sure it's functioning.
With it being summer, now replacing all the a/c servos in the dash and the leaky shrader valve seem all the more important priorities.


Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Michael,

What part barely passed? If you run your mixture too lean, hydrocarbons will go up. Also If the EGR tube is plugged, you will fail NOX. If you run anything less than premium gas in that model NOX will increase. EGR has to function on these cars. THe air pump is no help, because it only comes on at odd times like for 120 seconds at 40*c.

Peter

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Auto Zentral Ltd.

Peter,

It was just a few ppm less than the limit in NOX. So, I was thinking a stuck EGR valve. Maybe I should just check the line first.
I always use premium gas. The car had 70,000 miles on it last November and started horribly despite a recent tune-up. Mark Langston in Denver adjusted the airflow plate when it was in for a roadside waterpump, radiator, t-stat housing, and a/c charging.

I've been lazy on diagnosis- but hey I put the 500E euro lights in the car and can see at night!

Is there any special diagnosis skills beyond standard KE needed for a california emissified car? I think you mentioned code-reading was easier??

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E

Michael,

You say Kalifornia just like our new governor. Quite frankly I voted for aunold, because he is a breath of fresh air from politics as usual from a bunch of ATTORNEYS. He came to this country with nothing but a dream and made it work. Californians are pulling for him. We are going to have to make sacrifices, but we feel that he has the power to make opponents listen or pay the price. We feel that our new governer's position is that if you don't want to work with me, the voters will decide at the next election.

I'm sorry what was the question?

I'm not sure that your car even has EGR. You need to supply me with particulars about your car. The blinking light diadnostic didn't start until 89, so I believe that your car is going to have to be read with an on/off ratio tester at the round plug on the left fender well. The 89 Calif. standards were adopted by the Feds as OBD1. In 94 GM led the way for OBDII which oficially started in 96.

Peter

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Auto Zentral Ltd.

Hey,

Nothing serious was meant by the Kalifornia remark. I do think that in some respects, the other states follow California for better and worse. I've always found my diesel ownership to be politically incorrect in the USA.

Thanks, sounds like the 86' is probably more like the other 49 state stuff I'm use to.


Thanks again!

Michael

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Michael McGuire
83 300d
01 vw A4 TDI
66 Chevy Corsa
68 GMC V6 w/oD
86 300E