DME replacement

[ScottyWM]

So y'all may remember that I was having an error code 1286 on my daughter's E36 coupe. http://www.bimmernut.com/forum/showthread.php?t=42533
Well I finally got around to looking at it this weekend, and the error has changed to 1211 - DME self test. This kind of makes sense I guess, seems to be a common problem. Car still seems to run just fine, no change from before the CEL came on. I'm looking for the easiest fix here. I would think that would be to just replace the DME. Although if I get it apart and see obvious solder breaks I could fix them.

http://216.77.188.54/coDataImages/p/Groups/371/371092/folders/282967/2441480DME.JPG

Question 1 - how do I remove it, does it just unplug or what?

Question 2 - I'm pretty sure I can find a good used one. Can I just replace it with another Bosch DME M1.7? Or are they not interchangeable that easily?

After googling a bit, it sounds like I'd have to put my chip on any DME I replaced mine with, a 325 chip wouldn't work on a 4 cylinder DME would it?

[ScottyWM]

Thanks to a free handout from a nice local guy, I now have a replacement ECM to swap out with mine. Here's what I plan to do - tell me if I'm wrong or going to blow up the car.
1) disconnect battery, let sit for 1/2 hour
2) remove existing ECM
3) remove existing chip and put it into new ECM
4) install new ECM
5) connect battery
6) start car and pray

Can it really be this easy?

[Dave M]

Does the DME you've been gifted have the same part number? You may be able to use DMEs from different years, but double check first. I don't have a good source of 4 cylinder DME part numbers and compatability, but they're out there for sure.

Your plan of attacjk is fine. I never wait 1/2 hour t remove my DME, but it might be right thing to do. Also, getting at the chip wasn't as easy as I thought it would be on my first attempt. Have patience and good luck,

Dave

[bubba966]

No need to disconnect the battery to swap DME's.

When you disconnect the electrical connection on the DME you're doing the exact same thing that disconnecting the battery accomplishes, cutting power to the DME.

Being that it's a '93 there's no EWS codes to worry about. If the DME you've got is the same part # as what's in the car there's no need to swap chips. Just swap DME's. If the DME is a different part # I'm not sure what to tell you as I don't hear much about DME compatibility.

[ScottyWM]

I haven't pulled mine yet to see the p/n and RealOEM lists a bunch of different numbers for it. Donor DME is from the same year as mine, but it is out of a 325 and mine's a 318 - both autoboxes. Don't know how much trouble I could be causing trying to use the donor from a 6 cylinder in a 4 cylinder. I thought as long as I swap the chip I might be okay.

[Dave M]

I haven't pulled mine yet to see the p/n and RealOEM lists a bunch of different numbers for it. Donor DME is from the same year as mine, but it is out of a 325 and mine's a 318 - both autoboxes. Don't know how much trouble I could be causing trying to use the donor from a 6 cylinder in a 4 cylinder. I thought as long as I swap the chip I might be okay.

Two things.

1) I asumed when you were talking a bout "chip" you were referring to a 'performance' chip that you wanted to transfer to the new DME. Is this the case?

2) If you've been given a DME from a 325 (M50 engine), it won't do you any good in your four cylinder.

First step is get that part number and start searching for a new/used DME or find out what other part numbers may work.

Dave

[Ferret]

Two things.

1) I asumed when you were talking a bout "chip" you were referring to a 'performance' chip that you wanted to transfer to the new DME. Is this the case?

2) If you've been given a DME from a 325 (M50 engine), it won't do you any good in your four cylinder.

First step is get that part number and start searching for a new/used DME or find out what other part numbers may work.

Dave

Yeah, arent the DMEs different because they've got a different number of outputs?

They wouldnt fit 6 cylender DMEs to 4 cylender cars surely, as there will be a cost difference?

As Dave says, grab the part number off the existing DME and compare :)

[bubba966]

If it was me I'd be looking at electrical diagrams for the two DME's. There's not a whole lot different between the I4 & I6 of that era other than cylinder count (don't quote me on this though as I've not dealt with that I4 yet). It's entirely possible that the DME is the same, but the chip running the DME's are the only difference.


But I'd want to be damn sure that the DME's are identical except for the chips if I was going to swap them.

[bubba966]

That's an M42 in your '93 318, right?

And looking on the EAT site E30 M42's used 175 DME's. Not sure if they used the same DME's for the E36 as they did for the E30. But if so this guy in my local CCA chapter has a 175 DME he's looking to sell for cheap. I've not yet dealt with him personally, but have heard nothing but great things about him on the forum.

http://bmwpugetsound.com/vbb/showthread.php?t=43338

He's also got a good many other DME's as well if the one you have isn't a 175 DME.

[ScottyWM]

Yeah, it's an M42. Hopefully I'll have time this weekend to pull it out and see what DME p/n I have. Bubba, I'll keep you in mind. Does he know that these are 'good' DME's?

[Kibokojoe]

I have always heard to wait a minute or so with the battery wires taken off the battery and linked together. I guess this discharges any capacitors in the circuit. I used this to reset the computer on my sons 735i after we replaced the fuel injectors and repaired the AFM. It was a remarkable change. Went from 10 mpg to 18 in just a few miles.

[myles]

I think you'll be needing a DME from a pre 01/94 M42 engined car (that is USA E36 coupe or sedan). The 6 cyl cars all had DME 3 or later, but you need a 1.7. The DME will also need to be coded to your car if there are significant differences between the builds.

[genphreak]

I knew it. There's just no way a 6 ecu would run a 4. They can be different, therefor they must be different; Da BMW's production motto.

[ScottyWM]

Just to close this thread out, I'll let you know what I ended up doing. The Pelican Parts site has some good info and pictures on replacing the DME. When I got mine out, there was a little bit of moisture in the cavity it sits in (the common failure mode), but considering we'd had some torrential rains, it wasn't that bad. Removed the DME. Verified that the free donor was the wrong p/n even though it looked identical at the connector. Wasn't going to risk trying it, just had to make sure I got the correct p/n off mine so that I could start looking for a replacement.

Since I had it out, I opened it up expecting to see some corrosion or cracked solder joints or something. Saw nothing like that. In fact, it looked like new. Even looked at it under magnification (there's a lot of damn solder joints on that thing!) Only thing I could think of to do was to clean up the connector pins. They seemed to have a little bit of a film on them, and I thought maybe a bad connection was causing the DME self test code. Hit them with a little sand paper, hooked everything back up and Voila! Check engine light was gone. It's been a while now, and it's still gone, no codes with the stomp test.

So it looks like I got lucky. This car has been super reliable mechanically.