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Discussion Starter · #1 ·
Hey Guys,

I recently acquired a 2001 slk230 with 105k miles on it as I've stated in the intro post I made.

I have been doing a little bit of maintenance on it, to include changing the fan control module which was faulty and some other smaller things, everything was going smooth as butter until yesterday when I went to reconnect the negative battery terminal after I've disconnected it, like I always do if I am messing with anything electrical, but this time it was to see if I could clear the CEL after replacing my O2 sensor.

So some background first. I have previously disconnected my negative battery terminal to change out the fan control module which fixed my fan not working, obviously doing that required me to enter my radio code which I have and has worked successfully.

Today however I disconnected my negative battery terminal to do some work and when connected it back up to take the car on the test drive two weird things happened.

#1 the cooling fan doesn't engage anymore, however the low coolant light doesn't turn on like it did with the previous faulty unit and when I turn on the AC the fan does turn on but weakly.

Does that mean my module is going out again?

#2 This time around when I enter my radio code the radio doesn't accept it anymore when I know the same code has worked previously without any issues not even two weeks ago? Now, the previous code that I have entered was one that was written down for me by the previous owner, this one is off a little silver card I found in the car, and I can't for the life of me find the one the previous owner has written down for me. I have ordered a set of radio removal tools just to compare the serial numbers I have my my silver card to the one on the radio and eliminate that issue.

My question is, do these cars have some type of a fail safe fuse or something that when disconnecting and reconnecting the negative terminal can make it blow and therefor causing said problems? And also lets say that my fan control module is going bad again, has anyone just bypassed the stock one and created their own circuit with a custom thermal switch? I am asking cause spending $150 bucks every 2 months on this module could get a little costly at the end of the year hehe.

I have been doing quite a bit of searching on the forums, but haven't really come up with a solution to my issue, any insight would be greatly appreciated.

Thank you,
Mike
 

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Discussion Starter · #3 ·
As far as radio code, you can call MB and with registration/proof of ownership and the radio serial number, they will give you the radio code

or you can try a site like this:

Can't find your factory car stereo radio code? We can help!
Cool thanks for the heads up, I guess the first thing I'm going to do is check if the serial numbers match with my radio code card as well. I guess my real concern would be what if I do have the proper radio code and my radio is still being difficult, is the radio code stored in the ECU or the Radio it self?

I'm just curious if I could be experiences the above mentioned symptoms from just unhooking and hooking the negative battery terminal, I've been reading some horror stories of people partially burning out the PCM/ECU by just replacing the battery, just not sure if that is a possibility on these cars.
 

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I know you already disconnected the battery, but if you try one more time, leave disconnected for a minimum of 30 mins

then reconnect, try radio code and reset clock
 

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Discussion Starter · #7 ·
I actually came across the 30 minute idea right after I posted here. I have the battery disconnected as I am writing this and will report with results.

Thanks.
Well, I had the battery disconnected for about an hour from both the + and - terminal.

Once I re-hooked it back up I have had no luck, the radio was still in wait mode from me putting in the wrong code from previous tries, but it only took 3 or 4 mins to reset this time.

I guess at this point I'm just going to wait for my radio removal tools to arrive and confirm that I have the code fro the right serial#.

What worries me is that I'm almost 99.99% certain I have used that same code previously with no issues but you never know.

I guess I'll post back in here as thing start to unravel them selves.

Thanks for the input and guidance thus far.
 

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Sorry you are back to square 1. Did you mention how old the battery is?
 

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Discussion Starter · #9 ·
The battery is less then 2 years old and I don't have any starting issues or anything with the car.

The car starts right up and drives great, just my radio seems to be wanting to do its own thing and the radiator fan doesn't want t work hehe.

Does anyone know if the fan control module was bad would the fan still turn on with the AC on and should I get the coolant low light on on the dash as well?

I am thinking though, if I confirm that I have the right code for the radio and it's still not working, I'm almost certain it has to be some weird electrical issue, it just seems to coincidental that the radio and the new fan control box would both start giving me issues right after a negative battery terminal disconnect, but you never know, I've seen these cars do weirder things hehe.
 

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members will jump in. some will say to check for 'grounds' that might be 'shorting'
 

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It sounds like the previous owner replaced the radio... you're on the right track to obtain the serial number and double-check the code.

What exactly is "fan control module"? (picture?)

The "radiator fan always on" is the classic symptom of a failed K40. If that's what you replaced, you're probably just seeing normal behavior now.
 

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Discussion Starter · #13 ·
It sounds like the previous owner replaced the radio... you're on the right track to obtain the serial number and double-check the code.

What exactly is "fan control module"? (picture?)

The "radiator fan always on" is the classic symptom of a failed K40. If that's what you replaced, you're probably just seeing normal behavior now.
So the previous owner of this car has been my father, he purchased it brand new back in 2001 and was the only owner other than me now.

I'm not sure for 100% but he actually might have had it changed, I know for a fact that I did use a radio code last month provided by him but I don't remember now if it was the same one as on the "Radio Code Card" I found in the manual of the car and I can't ask him cause unfortunately he is no longer alive. But as soon as the tools come I will double check it. :).

As for the fan control module, here is a picture of one, its under the hood on the drivers side in front of the strut tower and it actually renders your fan useless not that it makes it run all the time. Only difference about this one going out is that this time the coolant light hasn't come on and when I turn on the AC the fan weakly turns on. Hopefully I start a much better and new job on Monday, if that is the case I will just buy a brand new one instead of a refurbished unit off of ebay.

As for the leaky cam angle sensor, yes my actually does leak a bit so thanks for the heads up. :) I already took the plug off and cleaned it up, but I will have to call Mercedes and see what they are willing to do for me, worst case scenario I'll just replace it myself no big deal. Also it doesn't look like the oil has gotten anywhere near the ECU but I did find some oil in the O2 sensor plug which I have already cleaned up. I still had to replace the O2 sensor because some idiot that replaced it previously never installed the plug properly and left the wiring all on the exhaust manifold, thankfully only the side of the sensor harness got burned up.

 

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As for the leaky cam angle sensor, yes my actually does leak a bit so thanks for the heads up. :) I already took the plug off and cleaned it up, but I will have to call Mercedes and see what they are willing to do for me, worst case scenario I'll just replace it myself no big deal. Also it doesn't look like the oil has gotten anywhere near the ECU but I did find some oil in the O2 sensor plug which I have already cleaned up. I still had to replace the O2 sensor because some idiot that replaced it previously never installed the plug properly and left the wiring all on the exhaust manifold, thankfully only the side of the sensor harness got burned up.
They did not replace mine, but did put in a new harness to stop the oil from traveling. Have it done sooner than later. It will kill your new o2 sensor.
 

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Discussion Starter · #15 ·
Quick question someone help me out here. So Mercedes Stealershop won't replace the leaking Cam angle Sensor/Solenoid without having to charge me a crazy amount hehe.

Anyways I just want to get it straight. Do I need to order the Cam angle Solenoid or the Cam Angle Solenoid?

For some reason I can't find a clear answer.

Thanks.
 

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Discussion Starter · #16 ·
Quick question someone help me out here. So Mercedes Stealershop won't replace the leaking Cam angle Sensor/Solenoid without having to charge me a crazy amount hehe.

Anyways I just want to get it straight. Do I need to order the Cam angle Solenoid or the Cam Angle Solenoid?

For some reason I can't find a clear answer.

Thanks.
Sorry, I meant to ask if I need the Cam Angle Solenoid or the Cam Angle Sensor? If someone could post a part number that would be awesome.

Thank you,
Mike
 

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Quick question someone help me out here. So Mercedes Stealershop won't replace the leaking Cam angle Sensor/Solenoid without having to charge me a crazy amount hehe.

Anyways I just want to get it straight. Do I need to order the Cam angle Solenoid or the Cam Angle Solenoid?

For some reason I can't find a clear answer.

Thanks.
The $tealership should put the wiring harness like I said though. I think you need the camshaft adjuster magnet.
 

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this is all I found. I don't have your vin number

 

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Discussion Starter · #19 ·
So just to give some closure to this thread in case anyone else searches for something similar. The other night I did find another 'Radio Code Card' with the proper code and that works now as well.

As for the radiator, I am almost certain that the 'Fan Control Module/Resistor' went bad again since I am sure ti was a refurbished unit. I ended up ordering which I hope is a new unit from Autohaus, hopefully this one will last me for another 100k miles like the other one.

Now I just have to do some research if its the actual cam angle sensor I need to stop the leak or the Adjuster magnet that goes over it.

Thanks.
Mike
 

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Discussion Starter · #20 ·
Hey guys quick update.

So a friend of mine told me that if a company like Mercedes has a recall on any part of a car, by law they have to change it if the car is 20 years or newer.

So I called a different Mercedes service center here in Chicago made an appointment with them and showed up.

Once I drove in the bay the staff people were super cool, the service guy that helped took my vin number typed into their system and what do you know not only did the Camshaft Solenoid recall come up but even my tail lights.

So at this point free of charge I am getting a new Solenoid, Harness, Ecu, O2 sensor and Tail Lights.

Makes me almost want to buy a new Mercedes because of this type of quality service and support.
 
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