1996 320 E Mercedes

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I have been trying to solve problems with my check engine light this entire summer. I have a 1996 E 320 with 150,000 miles on it. I bought the car new in '96. Lately, I have had a terrible time trying
to determine the cause of my check engine light coming on. I use a private car shop to do my repairs. He assured me that he could fix the car with no problem. He has replaced the knock sensor, the battery, the upper and lower control arm bushings the air mass sensor, and the rear oxygen sensor. The last time I took the car in, the owner of the shop decided to take my car to the local dealership to have them run test (says he didn't have to right equipment to do so.) He used their diagnosis to do the last couple of repairs. Overall this summer I have spent over $3000.00 on this car. The light has just come on again. He now tells me that the model E 320 that I have had a lot of kinks in it because it was the first year this particular model was made and that it is difficult to repair all the sensors. It's not him it's the car. Is anyone aware of special problems with the E 320? Any advice for me?
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My advice would be to forget it IF the vehicle is running ok . If not you'll have to take it to the dealer and let them figure it out . The control arm bushing certainly have nothing to do with the light appearing . I'm assume you had a different problem when the shop did that repair . When you have a 10 year old German car with miles on it , you're not going to live happily ever after. -Dana

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I don't know about "ever after" but we have 5 old benzes, 2 of my old guys have over 300,000 miles each and we're quite happy with them.
cp
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Hi Dana,
The car runs fine. It's just that I live in Ga and the car will not pass emission testing if it has the check engine light on. They will automatically fail the car. The dealership is my next step but I may just wait closer to the time that it's due for emissions testing. Thanks for your reply. Ballerinagul
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None of the issues you mention are unusual for a car with 150k miles. Power train trouble codes can be retrieved via most generic low cost code readers. Manufacurer specific codes however require the exotic code readers that the dealers have or the independent MB shops that made that capital investment. I really don't buy the "your car is new and has kinks in it rationale". It is usually used by mechanics that really don't understand the systems they are trying to fix. A lot of these guys are parts replacers that will keep replacing parts untill it is fixed or you run out of money. I would suggest you look around for another independent MB shop that has the equipment and trained employees to really fix the problem. My 2 cents Peter

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Thanks for your reply Peter, Should I look for shops that have exotic code readers? By chance would they have to be registered somewhere or do I just ask using that terminology?
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Thanks for your reply Peter, Should I look for shops that have exotic code readers? By chance would they have to be registered somewhere or do I just ask using that terminology?
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The check engine light indicates a fault and faults generate diagnostic codes. Our responses are total guesses unless you provide us the diagnostic code that's been generated by the check engine light.
Upper and lower control arm bushings are wear items that have absolutely nothing to do with the engine's check engine light so please stick to the subject and something might actually be accomplished.
I own a '97 E320 and would like to help you.
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Thank you for your response. I apologize for my ignorance about what is an engine light item and what is not. I'm looking at the latest work order that was a diagnostic test done by the dealership for my mechanic to use in repairing the car. It states that A 150383 short test. found in hfm -sfi- self adpt'n limit knock sensor 2 signal open circuit. nec. to perform hfmsfi individicual componetnt function test. nec. to perform fuel hyd. press test. found engine needs wiring harness, airmass me. ter, knock sensors. My mechanic in turnreplaced the engine harness, air mass sensor and rear oxygen sensor. To my knowledge, he did not take the car back over to the shop for an after-check. I don't know if that is necessary or not and I noticed that he only replaced the rear knock sensor and not the front one. The dignosis indicated knock sensors. Any help would be appreciated. And again, excuse my ignorance.
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I reread your original message. This 3.2L engine has been produced since about 1992. Yes, the 210 model CAR was new in '96 but not its engine or transmission. Your mechanic is mistaken to blame the car, IMHO, instead of himself for this mess.
Your choice is: 1. Learn much more about engines and codes than you ever wanted to know, or 2. Take it to a shop that has the M-B code reader and get their ESTIMATE to fix it, and 3. Relegate your mechanic to routine tasks like oil changes for that's his level of competence, IMHO.
I want to think about it a bit and will write again.
Tom
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You asked if there was anything "known" about this engine. I live in California and my '97 E320 gets a more through SMOG check than most other cars because this engine fails the test more frequently. I don't know why, there are lots of these cars here; it must be so statistically.
Let's start at the beginning.
Engine runs well but check engine light is ON. This started earlier this summer.
Does the dash board display show a message? Like "Check engine electronics"? If not, what? Was the engine last tuned up - new spark plugs etc. within the last 25K miles?
These parts have been replaced already: engine wiring harness ($ ouch), rear O2 sensor, rear knock sensor, and air mass meter.
Dealer suggests fuel pressure be checked and some individual components be checked.
There's not much else left to replace. Front knock sensor (I believe there is one), crank position sensor (I say that as an item, not necessarily as a candidate). This engine is also known to clog its EGR (exhaust gas recirculation) pipe; that could be a possibility.
I suggest you take it to a M-B dealer for diagnosis and a repair estimate. This will cost about $100. Don't whine, instead, say you're thinking of buying a new M-B in six or twelve months but in the meantime need to get this one fixed.
I too had a "Check Engine" incident, at 38K miles. My code reader reported PO170 "fuel trim". I asked others (here) what that meant - in English. Various possibilities were mentioned, too many to attack all. Paid M-B dealer $70 for diagnosis and repair estimate to learn: Air Mass Sensor: $500 - $600 estimate. Removed it, cleaned it and erased code, no "check engine" message so far, but it's still early days. Will replace it if message reoccurs; part costs $270 on internet.
You car's problem isn't solved but I hope this suggestion helps resolve it.
Tom
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Thanks for your suggestion. I will be taking my car to the dealership next week. To answer your question, the dashboard displays check engine electronics. New spark plugs have been put in 7k ago. The air mass sensor was replaced but the diagnostic referred to an air mass meter. Do you know if these are one in the same?
In looking at your list of what is left to replace, I can even narrow it down further .. the egr pipe was replaced in 3/05. The front knock sensor hasn't been replaced since 1999 so it is also a possibility.
I'm shocked that some of the parts can be removed and cleaned and still function as opposed to being replaced.(One of the things they never tell you)
I will keep you posted .
ballerinagul
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My fault: air mass meter and air mass sensor are the same - it measures the air inhaled by engine so correct fuel amount can be metered into the engine.
Well, I'll soon see if an air mass meter can be successfully cleaned. My car may still be in its code cycle.
I don't drive it much, 38K miles in 10 years. I have time to toy with things like an air mass meter.
I'm curious about your car's problem and would appreciate knowing the outcome.
Tom
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I have a 96 E 320 and I am having the same issue. Doesn't affect the car's performance as well. I have had the Mass Air Flow sensor replaced but continue to get an error that the codes are calling a adaptation error similar to your description. The next suggestion I am getting from my mechanic is to look at the wiring harness. Generally once he has pulled the codes and reset the car is fine for a few days/weeks. I also live in Georgia and got my emission checked a day after having it reset and it was fine.
I'm very interested in your outcome and look forward to seeing it posted if you find a resolution.
RW

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With many code check systems that you can purchase @ walmart, or have done @ you local AutoZone, resetting the check engine light is a small matter. Then take it in for inspection.
Collin
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That won't work. The engine's computer runs a cycle of diagonistic tests, X numbers of starts, so many warm-ups some miles at freeway speed before it illuminates the check engine light.
The code reader shows if one or more of these diagnostics is incomplete - exactly to prevent someone from erasing the codes just prior to an emissions inspection.
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Self adaption errors are caused when the air mass sensor and the Oxygen sensor don't agree. The air mass sensor measures the amount of air going into the engine. The ECU then injects the exact quantity of fuel the give the perfect fuel/air ratio.The oxygen sensor measures the exhaust gasses to see if the correct air/fuel ratio was achieved. If it wasn't, it can adapt its fuel mapping to allow for wear in the injection system. When the ECU can no longer compensate, it logs a fault and puts the light on. The Air mass sensor is a very common cause of this problem but you've changed this already. Other areas to check would be O2 sensor (replace), fuel injectors (can be checked at a Bosch centre) or air leaks after the air mass sensor.

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I have a 96 e230 with 160,000 miles on. I had a problem earlier this year with the coolant level light coming on. The level of coolant was ok and after running many test I ended up taking it to the dealer to get it checked. It tuned out that there was a fault on my window washer fluid sensor. ( yes .. the water bottle for washing the windows! ) This was very frustrating as the washer bottle light did not come one and the water bottle was full. Anyway, spent 20 on a new sensor for the window washer bottle and this fixed the problem. I don't think if would have ever spotted this with taking to the dealer.
I'm still amazed how the water level sensor in the water bottle could have caused the engine coolant light to come on. still .. the joys of electronic systems in cars!

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The two sensors are wires together in series and each sensor has a different resistance when switching. The instrument cluster uses a logic gate to translate the resistance in the wire as to which sensor has switched. If a sensor fails, the cluster gets confused and puts on the most important warning light. Simple.

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Yes, simple but a terrible design.
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