Check engine light - Mercedes Forum - Mercedes Benz Enthusiast Forums
Mercedes Benz Forums

Go Back   Mercedes Forum - Mercedes Benz Enthusiast Forums > Mercedes Benz Models > Mercedes E Class

LinkBack Thread Tools Search this Thread
Old 08-28-2006, 12:06 AM
Join Date: Aug 2006
Posts: 7
Default Check engine light

I have a 2000 E320. Ever since I went into service at the dealer, the check engine light came on. This was close to 6 months ago. I didn't really do anything about it since it seemed like everythin was fine. But now, the car is using more and more gas. It says that im gettin around 14.5 gallons to the mile???? Something is seriously wrong. I think it's the oxygen sensor. Would anybody know the location of it? Mercedes is too expensive for me :P... naw I'm serious.... help?
Reply With Quote
Old 08-28-2006, 03:07 AM
Senior Member
Join Date: Dec 2004
Posts: 2,409
Default RE: Check engine light

14.5 gallons to the mile!!! I think NOT.

Your car is fitted with OBD diagbostics. Get the engine computer scanned by any reputavle garage and the code will give you a clue as to what is wrong.
It could be the O2 sensors but it could also be a whole load of other things and not the O2.

Post the code (e.g. P0173) and we will tell you what it might be.

Reply With Quote
Old 08-28-2006, 05:38 PM
Join Date: Aug 2006
Posts: 7
Default RE: Check engine light

When I was driving my car to the gym today, at first it started at 8 gallons to the mile and after awhile it went up to around 15 gallons to the mile. I don't have anything to read the codes in my car. I went to ask Pepboys and they said it's $20 to pull the code and $80 to go in depth. Thats alot of money just for the code. I'm wondering if there is a smaller reader on eBay or something that I could buy that does the same thing. My friend has one for his BMW, would it work on my Mercedes? But do you know the location of the oxygen sensor so I can double check if it's faulty? Thanks ALOT!
Reply With Quote
Old 08-28-2006, 10:22 PM
Join Date: Mar 2006
Posts: 11
Default RE: Check engine light

Yes his obd2 reader would work on your car as well. Why are you thinking its the o2 sensor? Look for it on the exhaust its there.... but check to see if its faulty? You will need an o'scope and check and see if its working properly, a dvom wont read it well enough. good luck

-04 R6- 97 cobra -95 exploder-
Reply With Quote
Old 08-28-2006, 11:10 PM
Join Date: Aug 2006
Posts: 7
Default RE: Check engine light

o0o.. well the people at Pepboys said it's most likely the 02 sensor. Would it be possible to buy and new 02 sensor and replace mine in order to see if that's the problem? Is there any OBD2 reader that you would recommend?
Reply With Quote
Old 08-29-2006, 02:00 AM
Join Date: Apr 2006
Posts: 436
Default RE: Check engine light

You can DIY that sensor yourself. (my little two cents.)
Jorge Martinez
Anaheim Ca
1995 e320 SE Brilliant Silver Stock
1992 300e OG White Stock
Reply With Quote
Old 08-29-2006, 04:29 AM
Senior Member
Join Date: Dec 2004
Posts: 2,409
Default RE: Check engine light

Gallons to the mile. I think you mean Miles to the gallon UNLESS this strange readout is part of your problem.

Changing the O2 sensor is quite straightforward. However your car has 4. 2 per side. So which one? Changing them all without any good cause will be expensive and may not resolve your problem. You also need a lift to fit them plus you will no doubt have to remove some of the protective undertray from the car to gain access. They are located just forward of the two cats. One near the manifold. The other just forward of the gearbox.

Best way forward is to determine what the codes are.

$20 is a typical charge for scanning. Here in the UK it is £25 at an MB garage so I have my own scanner. Seems a lot to read a code but it still takes time and equipment to be able to do this.

Scanners cost a few pounds to a few thousand pounds so you need to decide what you want and why. Basic scanners only tell you part of the problem....just the basic code. Better ones also tell you flash memory information + real time readouts of the various sensors. i.e. you be able to check the output from the O2 sensor. Then there is the question whether you want a handheld, a Palm or a laptop readout etc.... I use and recommend a DynoScan system which is software which i have loaded to my Palm PDA. It does everything you could wish for on the engine trans and only cost about $150. However $20 is less!

Suggest you use your friends scanner....assuming it is OBDII compliant. Check pliug type (Trapezoidal in shape). This will give you some confidence that it is OBD compliabt. The socket is by the hood pull inside the car. It has a cover that hinges down so you need to look upwards carefully to locate it.

Since your car is a 2000 V6 I suspect you may have a P0170 to P0174. If so you have a MAF problem but it could also be so many other things.

Unfortunately ALL modern cars are fitted with MIL / CEL (Check Engine) lights. This light is to ensure the car meets emmissions legislation. If it is ON then something is not correct and needs to be attended to. the scanner is able to clear the light and sometimes it doesn't come on again for a considerable period. this doesn't mean that there was nothing wrong. Just that the conditions that caused it to come on haven't been experienced a second time. However on other occasions the light it comes on again immediately.

I hope this helps.

If you are hoping that you can correct this problem for minimum dollars you need a scanner.


Reply With Quote
Old 08-29-2006, 04:06 PM
Join Date: Jul 2006
Posts: 4
Default RE: Check engine light

I just did this on my 2000 E430. I once owned a 2001 E320 and the engine is similarly situated.
>A good code reader costs about $80 to $100. If you have a friend that has one and will lend it to you, use it. Code readers are universal for any modern car. The readers will come with a book that help you interpret the codes.
>The code reader plugs in right under the dash on the drivers side. There is a little door that flips open. Read the instructions for the reader... its pretty simple.... most are: 1) plug in, 2) turn the key on but don't start the car, 3) read the codes / page through the codes.
>If its O2 / Oxygen Sensor / the codes will point to Bank 1 or Bank 2 / Sensor 1 or Sensor 2.
>Bank 1 is the bank on which cylinder 1 lives. If you look at the head, you will see the cylinders numbered. On my E430, cylinder one (and thus bank 1) is on the right / passenger side.
>Sensor 1 on both banks is before the catalytic converter. Sensor 2 is behind the converter.
>If you have a check engine light for one sensor it is a best practice to replace all of them - or at least in pairs of front at the same time or rear at the same time.
>The rear / # 2 sensors are extremely easy to get to. I replaced both in about 10 minutes. I pulled the car up on ramps and these are easy to find. Its a unit with a wire - its screwed into either exhaust pipe. The wire is blue with a plug on the end. Just unscrew the old sensor and screw in the new one. I used a wrench - even though I bought an O2 sensor socket, the wrench was easier. I checked torque using a claw foot and I torqued them to 30 ft. lbs.
>The place to buy the sensors is They supply the real-deal, Bosch sensors that are OE at 1/2 the price of buying them from your MBZ dealer. I paid about $85 each for two rear sensors. Shipping was free and they delivered super fast. Be careful to buy the proper sensors for each bank and front or rear.
>My front sensors were not causing a fault. They looked hard to get to so I (stupidly) did not buy front sensors from AutohausAZ and did not intend on replacing them. However, I replaced my spark plugs. When I had all the coils off and all the boots removed, the front oxygen sensors on both sides were staring at me right through the gap between the firewall and the rear corners of the engine. >They are easy to see... screwed into the exhaust, blue wire running from them and plugged in near the top of the engine.
>With the front Oxygen sensors staring at me - and not wanting to go through dis-assembling the coils and spark plug boots again for at least another 5 years - I went to my local Benz dealer and bought the front sensors. These were list of $188 each. I got a little break at $160 each... about twice what I would have paid at AutohausAZ. However, it was worth it to me to get it done and not wait 3 days to have them delivered.
>To remove the front sensors I used a 7/8" claw foot on the end of a long socket extension. I had the claw foot, a 3" extension, a U-joint, then a 9" extension and maybe another 3". Both sides, it was very easy to maneuver the claw foot into place around the hex on the sensor. A quick twist loosened it. Both sides, I was able to reach it with my hand and back it out the rest of the way. (remember... all the coils, wires and spark plug boots were removed.)
>The new sensors have anti-seize already on the threads. I started the sensor by hand and then tightened it lightly with the ratchet. I switched to the torque wrench and torqued them each to about 30 ft. lbs.
>Voila! Done. I'm glad I did this while I had the space. Getting to the front sensors with the spark plug boots in the way would be a hassle - but probably not impossible. I'm glad I won't have to find out.
>The spark plug job is another story. It was a lot of work - but worth it. Plugs are under $8 from AutohausAZ vs. $~15 from dealers. And its a labor intensive job that I know by doing it myself its done properly.
Reply With Quote
Old 08-29-2006, 07:01 PM
Join Date: Aug 2006
Posts: 7
Default RE: Check engine light

so i guess i should scan the computer before i start replacing parts on the mercedes. Would it be possible to read the code in dept that i get off of my friend's OBD 2 scanner? I'm just wondering if it's better to go to Pepboys or some kind of store and have them run the codes instead. Also about the spark plugs, could that be the problem? So when the check engine light shows up, it's most like a problem with the emissions system? Thanks alot!
Reply With Quote
Old 08-30-2006, 04:40 AM
Senior Member
Join Date: Dec 2004
Posts: 2,409
Default RE: Check engine light

Yes it could be the plugs but there are 12 on your car at approx $10+ each plus they are time consuming to fit. A garage will likely charge 1 hour labour ($100? = $200 total!) although it is an easy DIY job if you have a good toolbox. (limited access)

Your car has good diagnostics onboard.

Ideally you want to not only get the codes but also the conditions that were prevailing when the fault occurred. Revs, speed, temp, manifold pressure etc.
In addition you can access additional data and something called STFT and LTFT (Short and Long Term Fuel Trim) is very helpful in understanding what is wrong. If the translated code is "Intermittent Misfire" it doesn't help very much. It could still be anything. The additional info all helps.

The scanner can also "reses" the light to OFF. Knowing whether the light comes back ON when you start or drive around the block (and if so what the conditions were when it came on for the second time) all helps. Sometimes just resetThe light only comes on when a set of conditions are not met.

Most low cost scanners can't provide the full data set. Dependent upon what code shows up the full data set is best. Check if the garage can provide you with a full code and data readout. If cost is an issue get the data using your friends scanner and lets see what that says to get started.

Once you have the codes give us as much info as possible like vehicle mileage, how long you have owned the car, service date and mileage etc.
Reply With Quote

2001, 300, 300e, 320, check, clk, e320, engine, light, mercedes, pepboys, plugs, reader, replaced, spark

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Check Engine Light check Engine Electronics nolen01 Mercedes E Class 2 05-07-2015 05:58 PM
My ETS light, BAS light, Breakpad light, break light and check engine lights are on Kikoap Mercedes M Class 3 07-30-2012 02:50 PM
My ETS light, BAS light, Break light, break light and check engine lights are on Kikoap General Tech 0 03-27-2012 10:37 PM
check engine, check electronics light solarant Mercedes E Class 4 12-27-2007 11:34 AM
94 E420 - Check Engine Light on, How to check? Mercedes E Class 1 09-28-2007 01:41 AM

Featured Sponsors
Vendor Directory
Our Sponsors
Monroe, WA 98272
All times are GMT -5. The time now is 09:07 AM.