Good Evening,

My check engine light has been on for quite sometime.. I was hoping maybe somebody on the forum can give me a few pointers on what to look for. Even though the light is on, the car is running better then new it has a ton of power and seems to drive normally.

All parts below where replaced. Some more than one time:
All four oxygen sensors (one was coding - failed - and was replaced a second time)
PCM (first replacement - reprogrammed twice, due to car would shake intermittently stopping at the stop light. Then replaced again due to check engine light)
both catalytic converters
Flow Valve

Other Parts:
pcv valve

Any ideas would be greatly appreciated!

 

You need to find out what the code is that's causing it to be on.

 

I'll have to bring it over to the dealer and have them give me the code

Thanks for the quick reply!

 

If you live near a Autozone they will read it for free.

 

An inexpensive code reader from Harbor Freight would be an invaluable tool to have.

 

Thank you both for your comments I will get back to you soon.

 

Ever get the code?

 

Yes.. I purchased the Bluedriver code reader and drove around with it for about a week. The two codes it prompted are:
P2096 - Post Catalyst Fuel Trim System Too Lean Bank 1
P2099 - Post Catalyst Fuel Trim System Too Rich Bank 2

In addition, BlueDriver had the ability to collected live sensor data which I sent myself each day.. After compiling the information I noticed some deviations under "Distance Traveled while MIL "Engine Light" Is Activated(miles)" and "Engine Coolant Temperature" The rows of information that had deviations I highlighted in yellow, the actual issue I changed the text color to red. See attached PDF.

As of last week the dealer advised to change out the engine harness. Instead of cutting wires and creating more problems.

The car itself is running better then new. Since they changed out the cats it has a ton more power!! But, as somebody who like to make sure the car is in perfect running order I would like to find out what is keeping the Engine Light on.

I appreciate all your help. thank you again!

 

Weird readings for 10-15 seconds? Do you see this on your temp gauge? Did the stealership recommend to change the sensor?

 

Wow, I love that display readout!
1st thing I would do is look at the coolant sensor itself, wiggle the wire, unplug it, clean contacts, that sort of thing. I can't even guess how much a harness would cost to replace.

 

I do not see any issues on the gauge cluster, the temp sensor is not giving errors so they are not replacing it. The other issue I noticed is the miles the engine light has been on it will count normally.. 300, 301, 302 then jump to 20,000 maybe 50,000 then go to 303, 304, 305, etc..

lastly, I question the Bluetooth connection between the Bluedrive and iPhone not sure if the information sent somehow gets corrupted due to the wireless connection which could also be a factor.

 

I am waiting for the dealer to get back to me. I will look for the connection make sure it's tight and clean.

Thank you

 

As for the real codes, try monitoring O2 readouts live via OBD2, if issue persists.

 

I forgot to mention there is about 200 pages of data i went through. The six pages I uploaded are a snap shot on when the issues occurred. I kept a few entries before and after to show normal readings.

 

The O2 sensors have all been replaced one has been replaced twice. I think it has to be another issue causing the failure..

 

Typical trouble shooting advice from a dealer - If you keep going to a dealer, this kind of asinine advice is all you are going to get.

It is apparent that you are willing and able to deal with this yourself, why bother with going to someone who knows next to NOTHING about your car?

MORE foolish advice. The sensor can produce inaccurate readings, BUT provided they are within the defined range, there will be no code.

And it works both ways - my car was throwing O2 sensor codes as well as misfire codes. I changed all plugs and plug wires, but not the O2 sensors - this stopped ALL codes. My misfire codes were due to real misfires and my O2 sensors were reporting out of range oxygen levels NOT because they were defective, but because they DID see REAL oxygen levels that were too high because the misfires meant there was too much oxygen in the exhaust.

A DTC code for any item does NOT automatically mean that item is defective, it may be that it is reporting abnormal readings because that is precisely what is happening.

I think you'd be no worse off chasing this yourself (maybe with some help from us) than running back to the damn dealer. If you need experienced, professional help, take the car to some local shop that is KNOWN for Mercedes experience. Anyone who has chased similar issues in an SLK320 or one of it's cousins will likely already suspect what is going on, as he has seen it before.

 

One other thought:

if the ECU sees intermittent low coolant temperatures (whether by wiring or sensor issues), won't it go into "Warm Up" mode? And in "Warm Up" mode, the expected O2 levels are higher.

He!!, there's an electric pump to push it through!

IDK-just asking...

 

Good one, Max.

 

Thank you for your knowledge and advice. I am somewhat comfortable under the hood, I just need to know where to look and the process to check/fix/change. If you know where I should start - I'm all ears.

Some additional history My crossfire has roughly 53k lightly driven miles on it, I baby it by changing the oil every 5k and also dump a bottle of injector cleaner in the tank.

Thank you again for your response

 

That sound reasonable, do you know where the sensor is located?? I can see if there are any wiring issues.

Thank you for your reply..