DME and aux fan error
 

Hi everyone,

My E53 seems to be hungry for new parts again. LOL. Been having issues with the aux fan not working even after repaired. Turns out that the DME is sending "some" signal but not the right signal to activate the fan. Saw the scope and it's definitely not a square wave...so, I have a choice to make.

1. Send out the DME for a repair/rebuild...though the fan circuit is all that is out at this time
2. Indy suggested we put in an electric aux fan and a relay that will kick it on when the AC is activated.

Is there any downside to having a fan run anytime the AC is on? I'm not an AC specialist. I'm not against fixing the DME but I must admit that I find it attractive to replace the PWM fan with a simpler solution.

Pros/Cons appreciated so I can make an educated decision to stay stock or to make a change to my vehicle operation.

Depends on your driving. A daily driver will eventually burn up the fan. Above 30 MPH, most condenser fans turn off. A trinary switch would work. I've installed trinary switches on A/C high pressure lines. Unfortunately, our E53s don't have a shrader valve port. A trinary switch would simply screw on.

Does anyone know how the pressure switch works? You could grab a relay signal from there.

You just helped me make up my mind. I'll pull out my DME and send it out for a repair and simply reinstall it. Found a DME repair service for $275...so I think I have my answer. Hadn't thought about this long enough to realize that living in the desert, the AC would be on almost all the time. That would likely burn up a fan and create more issues in the long term.

DME repair here I come. Heck, had the ABS unit rebuilt so maybe the DME was just not feeling the love. LOL. :rofl:

LOL, good info helps make decisions. Who is rebuilding your DME? I may need rebuild my GM3. So far, I keep hitting dead ends on no sleep mode. Sending out the GM3 may solve my issues.

I'll probably use these folks: https://www.g7computers.com

I used a firm in SoCal to do my ABS rebuild last year but they don't do ECU/DMEs.

So you already checked the connectors on DME so there is no corrosion on pins? Very rare that PWM circuits fail on any BMW engine ECU.

Is there a reason your indy did not just plug the new fan in to test it before ripping out the old one and putting in the new one?

I literally did that last night, when finally getting around to fixing this issue on my x5 (where we live, an aux fan is not as critical as it is in most places this time of year, so I've been putting it off for a long time).

There are many ways to actively get the ECU to turn the fan on, but for me it was easiest to command the active test using my foxwell. It spun it up gradually and then held it at full speed for a while before letting it back down. Prior to buying the new fan, I tested the system thoroughly to make sure the signal was being sent, but the fan was not doing its job. There is another thread on here where I provide a ship ton of info on that.

Of course, the foxwell commands go through the ECU, so if you really do have a problem with the ECU or the wiring, failure will not be conclusive.

BTW, that fan (I got a TYC - about $150 at RockAuto.com, highly rated) is incredibly powerful. I would similarly be concerned about having it set on full speed all the time the AC is on. I joked with my kids after opening the box that I was going to install a propeller on the front of the x so it would go faster, and now realize that's not completely joking.

So if your indy could have done that test but does not have a good reason why he did not, I'd factor that into any further consideration of his advice.

Good luck.

+1 on this

I also recently replaced my aux fan on my ‘05 X5 3.0…

I tried to activate my old on with INPA…NO LUCK..

I also bought the TYC fan on Amazon.. tested it before install and it fired right up.

If the DME is really at fault, it's likely the result of some testing/jumpering by someone not knowing what they are doing.

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I have only seen cases where the DME had corrosion from coolant leaking down the wiring from the tstat connector making it's way to the DME and causing a fan activation issue. I have also seen on a higher mileage e39 540i the vanos solenoid allowing oil to leak through them, down the wiring into the DME connections as well. There would be obvious signs of an issue when physically checking the DME connectors...

No signs of any issues at the DME. Corrosion free. Its important to remember where I live though. Like EODguy I'm in the desert and our temps here along with the low humidity can cause electronics to fail.

The wire is good between the DME and the fan as it gets variable voltage and a signal. The signal is supposed to be a square wave but a scope shows that is not the case with this DME. The DME also is unable to see the fan acknowledgement at startup (as the fan doesn't get a correct signal...it doesn't turn on...and so the voltage generation is not seen by the DME) and sets a code for Fan Activation error.

I've grown accustomed to electronics failure in vehicles. If you recall, I had an ABS unit fail that actually caused my car to go into Trans Failsafe with a code for a bad transmission speed sensor. Turns out the ABS unit and the Trans Control Unit had a disagreement on the speed of the vehicle and the E53 assumed it was a trans issue and not ABS. Sent out the ABS for a rebuild and all the gremlins were gone again. I'm going to hazard a guess that once I have this DME rebuilt that the brand new fan will indeed work. If not, then I'm at a loss and will look at it again. :)

You are probably correct but It might be worth trying to get a spare DME, EWS and key just to see if the spare DME will activate the fan. You may be able to just plug in the spare used DME and see if it will activate the aux fan. The full pkg is really only required if you plan to start the vehicle. I have a few spare 4.4 mE7.2 DMEs which should be sufficient to use as a test...

Let me make sure I have this idea right...get another DME/EWS pairing and a key that's stored in the EWS. Install the DME and EWS...and then also change the lock cylinder so the key turns....and then check the fan activation?

Couldn't I just code another DME to my VIN and synch it to my existing EWS using my Foxwell and get the same result or am I missing something?

DMEs are a 1 time write so that can't be done without specialized tools and alot of me7.2 knowledge to erase the ISN so you cant pair a used one as the EWS will never accept it due to the mismatching ISN. However, for testing purposes I think you can just plug in the used DME turn the ingition on (DO NOT attempt to crank it which may unpair the original EWS and original DME which can be repaired easily since it has your original matching ISN as long as you have some kind of software that can pair them back up) and see if the foxwell will activate the aux fan.

Here is a good example on e38 bimmerforums: see post #36
I think he is also in Florida

https://www.bimmerforums.com/forum/s...-on&styleid=50

For fan activation purposes any same type DME will do the job.

A used DME can be cloned for your VIN and EWS info. Some modules like diesel DDE4 there is only one 8 leg chip (ST Microelectronics) (same type as on instrument cluster) which contains this data and can be swapped from original ECU.

I've got the DME and EWS packaged up. I also purchased a used and matching DME so they can clone it for me as well (and I can put it on a shelf).

I've never found a way in Foxwell to activate the fan ...but I do have INPA so I can get around it.

There are a few ways that *should* activate the fan. I looked into that when confirming my fan was dead. The following thread has a bunch of off topic stuff, but if you can sort through that, there is good info in there:

https://xoutpost.com/bmw-sav-forums/...-fan-woes.html

I know it is often a treasure hunt to find the Foxwell features you know should exist. Here is the sequence that runs the fan active test on my 2001 3.0i using my Foxwell NT520 Pro:

You start by going into the BMW diagnostics and do the automatic VIN ID (that no longer works on my car) or manually tell it what model you have.

When you run the actual test by hitting the F3 button to "activate" it will do nothing for a second or two, then gradually ramp up the speed over about 10 seconds, holding it there for a few seconds before spinning it down. Very impressive I have to say.

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EDIT - also, I never ever got any codes related to the dead fan. BTW, finally and completely confirmed dead when the replacement fan worked perfectly. As far as I can tell, that Foxwell test sends commands through the ECU to the fan, and you are supposed to watch to see what happens. There is no success or failure signal that comes back.

Cool! I was looking for fan activation on my NT520 Pro. My fan works. I installed an aftermarket brushless fan. I'm still looking into why it does not start up at A/C demand. Once the engine is warm, the fan kicks on. It ramps up on heat demand.

ok...so, I just got another Foxwell scanner (530)...and I'm hunting for this exact menu. Can you give me the tree? I've gone into Diagnosis, DME...but no active test menu. It gives me ECU info, Read Codes, and Clear Codes ...

If post #18 above does not answer it for you, then I don't know. Good luck.