So my engine fan is still constantly running on high on my crossfire. As soon as I start the engine it kicks in on full blast. I've already replaced the fcm three times, didn't work. I've also replaced the mass airflow sensor and had an ecu reset, and the problem still continues. Car runs fine, just the fan is always on full blast. Only thing I can think of now is the temp sensor but my gauge works fine. Any thoughts ???

 

Is the "Low Coolant" light on? It's on the left end of the dash, to the left of the Temp/Fuel gauges.
It's yellow and looks like a little radiator - and there are SEVERAL things that will make the light come on. Think of it as a "General Cooling System Alarm Light".

Read my post in the other thread (you know the one, the one you posted in earlier today).

If the light IS ON, then the ECM and FCM are not talking to one another - and that will be somewhat easy to fix.
If the light is NOT ON, then it sucks to be you - JUST KIDDING - but if it is NOT on, then one of three things is going on:

• The ECM is off in la-la-land. It is not sending pulses to the FCM so the FCM is running in emergency mode like it is designed to when it does not hear from the ECM every so many fractions of a second. Try shutting off the engine, disconnecting the battery cable - and leaving it off for five minutes. Reconnect and see if the ECM gets it's brains back in order like with the guy in the other thread.
• The ECM has good reason to run the fan at high speed and is doing so, intentionally. The challenge is to find out what that reason is. I will try to help all I can but with your temp needle working, not sure where to go with this.
• Your ECM is bad. I have a very hard time believing this one.

 

I don't have the light and I've already tried disconnecting the battery several times. The light comes on when I disconnect the fcm and turn the car on if that means anything

 

The problem started when I was replacing the mass air flow sensor, and I started the car and drove it before plugging the mass air sensor, when I realized and reconnected it the fan came on high and the car went into limp mode. A friend used a diagnostic computer to get it out of limp mode but the fan never went back to normal

 

I'm afraid this is going to require a trip to the dealership😲 , like he said, it sucks to be you.

 

That proves the connection from the FCM to the ECM is good.

WHY is the ECM telling the fan to run at full speed - damn, this is a head scratcher.

 

In seven years, the only reason I went to a dealer was to get the TPMS programmed.

As for me - I'd never tell him to see a dealer. This is a GOOD one............................................... .....

 

Very few people other than the dealer has the computer and software that can access the inner layers of the ECM that's the only reason I said this is going to require a trip to the Dealership in order to reprogram it. You're right I normally would never recommend anybody go to the dealer but this unfortunately is one of those instances where I'm afraid you will have to.

 

EXACTLY same thing happened to me, forgot to plug in the IAT/MAF after having the Gen 1 NeedsWings CAI off. Fan ran at full speed and got a CEL. Only difference is that when I plugged mine back in and reset the CEL, all was back to normal.
Makes me think :
You either did not get it reconnected properly, or it's not making proper contact, or you cleaning it destroyed it.

 

I was going to agree with post 8, but I think post 9 NAILED it.

 

Absolutely worth taking into consideration and exploring may end up saving you a trip to the dealership

 

Who has EVER had a resolution to an electrical issue at a dealer that did not take WAY too long and cost WAY too much.
I'v seen topics, "After six weeks at dealer, still no start..." and "Two months, still runs rough..."

That is not a solution, it is just another problem. When Tricials' car would not run, she took it to a dealer AND a local MB shop. Weeks went by - the car was fixed by Charlie when he came over with a spare TB. All three of us learned about the car that day - and he had it running fine in an hour!

 

Well sure, why wouldn't Charlie be able to fix it ?
After all, he's German, the car's German, they speak the same language ......
( Maybe I should get a CD of German language lessons ? )

 

No, just drink heavily and daily - THAT is his secret.

 

I wish to go back to this post I just made. A big reason why Charlie was succesful was because he did not troubleshoot the car as 'mechanics' and 'technicians' are trained to do these days - that is, by following the 6th-grade-level advice in the service manual.

Charlie used experience and logic to determine this. We KNEW the ignition system was fine, we KNEW the intake and vacum lines were all ok. Tricia had changed the MAF/IAT sensor herself. (once with an Autozone piece of crap, then with an OEM part). What else could we have here? There was talk of replacing the ECM ($1800) - but for the ECM to be causing this would mean that ONE ROUTINE of the code in the ECM had to be 'defective' while the rest of the code was OBVIOUSLY ok. How do you explain that? Could it be that the transistor on the ECM that drives the TB be leaky? (Sure, but what are the chances of THAT?)

But the "techs" don't think like that, they have NO experience in microcontrollers - and with the divorce from Diamler/Benz, they have no tech support to speak of.

No, dealers are handicapped and it is NOT all their fault (I KNOW I make it sound like it is, but that is not intentional.) Fact is, you are taking a Mercedes Benz SLK320 (with some modded code in the controllers and a different body) to a Chrysler dealer, that CANNOT go well for you. And it very rarely does.

 

What is the CEL? and how do i reset it? i'm still having this issue..its extremely annoying, also how would i know if the ECU is bad ?

 

CEL > Check Engine Light
Read the OBD II diagnostic codes, write them down and tell us what they are, then be sure all of them are cleared.
Did you replace the temperature sensor?
You may have a short in the wiring harness giving the fan electric power.
When replacing electric parts be sure you use OEM/Bosch/Mercedes replacements. The generic brands at retail auto parts stores often fail to preform as required.

 

Why was the MAF sensor replaced in the first place?
Can you put the old one back?
Try to go back to square one when you get into a predicament like this.
Did you replace the sensor once or twice?
Always start your post of with the problem and all the facts not add facts later.

 

I haven't replaced the temperature sensor because my temp gauge inside the car seems to work fine, I don't have a check engine light but I can still get a diagnostic. As for the wiring harness, I'm pretty skeptical that it is that because of the way the problem started. I left the MAS unplugged accidentally while driving the car, then when a plugged it back in, car went into limp mode and wouldn't go over 5MPH. Had a mechanic take it out of limp mode but fan came on after doing so. It has remained on ever since. That was about a year ago

 

That how the problem started, I was going to replace the MAF because i was having a jerking problem. Though after I replaced it i forgot to plug it in before turning the car back on and driving it...I ended up replacing the sensor again because i thought i may have damaged it while replacing it the first time because i dropped it a couple of times