So, I took my MC in last Thursday because the sunroof had a clogged drain and it was dumping water into the passanger side of the car. Anyway, while at the dealer the discovered that my engine cooling fan was always comming on. There was no coolant leak so they replaced the fan.

Well, they still have my car because replacing the fan didn't fix the problem. The dealer now tells me that they are pretty sure that the engine control unit is faulty and they have sent a request to Mini USA so that they can replace it.

I was just wondering if anyone has had any problems with the engine control unit. I did a search on the forum and couldn't find any entries. The dealer has been great plus the car they gave me to drive is a 2007 MCS which has been tons of fun. I'm just bumbed to not have my own car.

 

Two little comments: Did they turn off the AC? The cooling fan comes on when ever the AC is on; The ECU acts on sensor data inputs. Have they located and checked the coolant temp sensor? If the sensor sends a false signal to the ECU indicating an overheat condition the ECU will command the Coolant fan to come on. You drove it there= ECU is working.

 

Mininut - The dealer did check for a coolant leak and also checked the sensor. These were the first things that they did. Like I said they also replaced the fan which also didn't fix the problem. It's cold as hell here in Columbus, OH so no the AC has not been on. The fans low speed is not coming on, only the high speed. This remained the same when a new fan was installed. This is one of the reasons that they feel it's the ECU.

 

I'd still look elsewhere then the ECU. I still think the ECU is getting erroneous data from the sensor. I'd be looking for ground faults and or shorts in the wire from the sensor. There is also the probability that they replaced the fan with a bad unit though improbable. I believe that the fan has a resistor in it that controls the speed of the fan. The fan's default is to the higher speed if the resistor malfunctions.
Don't bet that you don't have the AC on. It's cold there and you have been defogging your cars windows,right. When you hit the defog button you activate your AC. With a bad resistor in the fan control you default to the higher fan speed. Don't get me wrong, I always use the KISS rule and the stuff I suggest is to eliminate the obvious first.

 

I had an Audi die an untimely death becasue water leaked in thru the plenum and killed several of the computers, point being I wonder if the sunroof leak contributed to the problem?

 

Hmmm.... while I know folks are iffy about playing with something as expensive as an ECU module..... seems pretty simple to troubleshoot if you could get your hands on a known good ECU for 5 minutes.... plug it in... fan will either run or it won't.... ECU theory either proven or disproven.

 

I sincerely doubt the DME is at fault, only have had to replace 1 ever, but it's definitely a possibility. I'm sure they know what they are doing, they know the obvious signs, hope they checked the relays, they have been known to go bad. And in order for a DME to be replaced under warranty the dealer must submit a PuMA case and have it authorized, and after that they'll probably have to send it out to have it programmed unless they have the newest programming ISTA-P.

 

This should not be a mystery for the dealer to trouble shoot, wait I take take back since they seem to be using the shotgun approach.

The ECM provides a ground to the coil of an external relay; it,s contacts closes and provides power to the coil of the relay located on the fan shroud.

The relay contacts on the fan shroud then closes and power is delivered to the fan motor.

The first thing they should have done is unplug the external relay; if the fan stops then the ECM is energizing the external relay which causes the fan to run, but instead they choose to replace the fan??????

The engine coolant temp can be monitored with the OBD scan tool; the low speed will come on at 105c and high speed will come on at 112c.

The A/C compressor will not come on if the ambient temp is too low; this is by design.

If the high wattage resistor on the fan shroud opens, you will loose low speed, then high speed will come on when the temp reaches 112c.

The temp gauge will remain in the middle; however when the temp reached 120c (just 8 degrees more) the temp gauge will immediately go to the max temp position and remain there until the temp goes back down; this is by design and is intended to alert the operator before the engine is destroyed!

I hope this repair is at no cost, because they are guessing. Good luck and I hope this helps!

 

Well, the Mini dealer called today. BMW is having them check everything out before they let them replace the ECU. I was told that there's a good chance that I'll get my Mini back today. They were in the process of checking all of the relays and switches when they called.

I guess once they put this ECU in my Mini it will be programed to it and they can not put it in another car. This is the reason that BMW is having them check everything else first. I'll post again the the next day or two to let you know what they did to fix this problem. And yes, this is all covered my by warranty.

 

Given the shotgun attempt they tried initially that seems reasonable. Had this been on my dime and they had replaced the cooling fan with no appreciable change and then claimed that they needed to replace the ECU I'd have gone ballistic. I'm glad they are finally trying to diagnose the problem.

 

I picked up my Mini today and they did end up replacing the ECU or DME (as it is called on my service sheet). They wrote three paragraphs about everything that was checked before the new DME was installed. As soon as it was replaced, the problem was resolved. I'm just happy that when I turn my Mini off that fan isn't blaring on and on for 5 minutes. At first I thought it was normal, that was until I turned it on just to set a couple of setting on the CD player and when I shut the car off the fan stayed on. Anyway, I'm just glad it's fixed. I'm also glad that I have an extended warranty in case something like this happens in the future.