- Project Time: 3-4 hours
- Tab: $30
- Talent
- Tools: Plastic garbage bag, set of Torx sockets, metric wrench set, metric socket set and ratchet, electric drill, .375-inch drill bit, 1/2-inch conduit punch, 3/4-inch conduit punch, file, primer, WD-40, oven, soldering iron, solder,
- Parts Required: Water drain hoses (2), valve cover gasket
- Performance Gain: An engine that will start and will run properly
- Complementary Modification: Replace the DME (if it couldn't be repaired)
The Bosch Motronic Engine Management system is what controls the ignition, timing and emissions controls of the later-model 3-series cars.
As such, it can be considered the brain of the car. The ECU (Electronic Control Unit) will cause the engine to run poorly or to stop running altogether if it becomes damaged. In this tech article, we'll talk a little about the DME, how to troubleshoot its problems, prevent damage to the unit, and repair or replace the unit.
Read the Codes
First, if you are having problems with your car, you should check to see if the computer is giving out any fault codes. See the Pelican Technical Articles, Code Reading and OBD-II Diagnostics for more details. If the code readers are having trouble connecting to the unit, then you need to look further.
DME Relay
Many people I have spoken to have had problems with the relay that controls the DME computer itself. It's not uncommon for the main relay to have its contacts become corroded and fail to work 100% of the time. Even if the relay is intermittent, it might show up as the engine running rough, or stalling, or any other number of failures. One of the first steps I would take is to identify this relay (on E36 BMWs, it's relay number two, the white one, next to the fuel pump). Try swapping it out with a known good one if you have one, or swap it with another one on the board (like the one for the fog lamps). Try starting the car. If you see an improvement, then you might have found the problem. Start with the relay - it is the easiest and cheapest item to replace.
Early E36 DME Compartment Flooding Problem
On E36 BMWs manufactured prior to July of 1994, there is a design problem with the car that has caused a lot of problems with the main DME computer. The water relief channels of the car are not beefy enough to withstand a significant influx of water onto the car, or the windshield. While perfectly adequate for anything that nature may throw at the car, the channels are woefully inadequate for a car wash. If too much water is used, or if the water channels are clogged with leaves or debris, the water will overflow and leak into the compartment where the DME is stored (see the Pelican Technical Article on DME Chip Replacements for the location of the DME in the engine compartment). I have heard stories of owners who have opened this compartment, only to have a gallon of water or more come flowing out. Needless to say, having the main computer for the car submerged in water is not a good thing.
How exactly does the water get into the box? The DME compartment is located right next to the intake plenum cowl for the heating and air conditioning system. This cowl is open to the enviroment, and thus will get rain water deposited into it. There are drains at the bottom designed to drain this rainwater. However, if the volume of water is too great, or the channels become clogged with leaves or other debris, this plenum will overflow directly into the DME compartment. If enough water fills this chamber, it may also leak into the passenger side foot well, although this often goes unnoticed, as the water will leak under the passenger floor mat.
BMW has issued a Service Bulletin and a relatively inexpensive fix for the problem. The fix is to install a third drain and use an improved style of drainage hose. The BMW factory bulletin that describes this repair is 41 03 93 (3914), and is dated July 1994. Begin by removing the plastic screen covering the plenum, the portion of the plenum that covers the firewall, and move the wiring harness out of the way on the left side of the engine compartment. Then remove the cylinder head valve cover - you will need to do this to gain clearance for working (see the Pelican Technical Article on Valve Cover Gasket Replacement). Cover the top of the engine with a drop cloth or plastic garbage bag to prevent anything from falling in.
Now, pull back the insulation that is located against the rear firewall. Remove and throw away the right side plenum drain hose at this time (Figure 1). Behind the firewall material, there is a circular area pre-stamped in the firewall just above and to the right of the original drain location. You will be drilling out this hole and installing the new drain hose in this hole. BMW specifically recommends against using a hole saw here - the metal shavings are too likely to contaminate either the engine or the plenum area. Instead, start with a .375" pilot hole and use a 1/2" conduit punch. Then, use a 3/4" conduit punch and enlarge the hole to 28.2mm (1.11"). File off the edges, paint with a small bit of primer, and then reinstall the firewall insulation. Drill a corresponding hole in the installation, and install your two new drain hoses (part number 51-73-8-144-152), slightly angled 30 degrees towards the center of the car. That's the BMW fix described for this problem. Figure 2 shows the area where you need to drill (yellow arrow), and also points to the oil drain hose (green arrow) that should be pulled out and replaced (behind the cylinder head, which in this photo is covered by plastic).
If you are not fortunate enough to have read this article before your DME got toasted, you may still have a chance to revive it. Open the DME compartment and remove the DME unit (see the Pelican Technical Article on Chip Upgrades for more details). If your DME is covered and soaked with water, then you may be able to save it. Take the unit apart and expose the two circuit boards (Figure 3). Although I have not used it myself, I have had several Pelican Parts customers tell me that spraying the board with WD-40 helps to dispel any water, dries the board, and sometimes works. The board is already soaked in water at this point, what could it hurt? Take the DME boards and place them in an oven set at about 100 degrees, and let it sit for a few hours. This should help evaporate any remaining water that may have made it into the unit. Reassemble the unit, and plug it back into your car to see if the problem still exists. If it does, then you will probably have to replace the unit with another one (see this topic later in this article).
Cracked Solder Joints
Some DMEs stop working for reasons that don't seem obvious (like being submerged in water). If you borrow a DME computer from a friend and your car works perfectly, then you have indeed isolated the problem to the DME circuit board. It is possible to sometimes inspect and repair these units. The most common failure associated with old electronics units are cracked solder joints. Have you ever had a Walkman-type stereo that had a broken head phone plug? If you wiggled the plug one way, you could hear, but if you let go of the plug it would stop working? This is a symptom of a cracked solder joint, and it can occur in your DME as well.
If you take a close look at your board, you may be able to spot a cracked solder joint. Some broken joints are not able to be seen with the naked eye though. You have a good shot at repairing these joints by simply reflowing the solder at large solder connections that seem like they may be attached to components that give off heat. The heat causes the crack to enlarge and then may separate, causing an intermittent failure. The same thing can happen if the DME is rattling or exposed to excess vibration.
To repair a cracked solder joint, simply get out your solder arm and reflow the solder (Figure 4). In a unit that I am repairing, I usually like to reflow the solder on all the joints that are pretty large, and particularly the ones that look like they are attached to heat sinks. These are most likely to experience cracks and failures.
DME Swapping
Finally, if you've tried all of the approaches outlined above, and your DME unit still doesn't work, then you will probably have to replace it. A little known secret is that many of the DME units are exactly the same across different automotive manufacturers. The only thing that is different is the programming chip contained within the unit. If the DME unit is the same version of Motronic, has the same connector on the unit, and has a removable chip, then chances are it can be a good replacement for your failed unit. This means that a $10 DME from a Volkswagen in a junk yard may work in place of the $650 one that a BMW used parts dealer wants to sell you. A few customers have experimented with this by swapping BMW DME computers with the ones used on the Porsche 944 and 911, and they have experienced good results. Some units won't work (it's a matter of trial and error), but many will. The main thing to remember is that you have to have the same software version of Motronic, the connector must be the same, and you must swap the chip from your DME to the new one.
Although I haven't done enough testing to generate a table of replacement units that will work, here's a table that shows most of the models, engines, and DME versions for BMWs:
| Model | Chassis | Engine Type | Year | Bosch Part Number | Motronic Version |
| 318is | E30 | M42/B18 | 90-91 | 0 261 200 175 | Bosch Motronic M1.7 |
| 318i/is | E36 | M42disa/B18 | 92-12/93 | 0 261 200 990 | Bosch Motronic M1.7 |
| 318i/is | E36 | M42disaII/B18 | 1/94-12/94 | 0 261 203 282 | Bosch Motronic M1.7.2 |
| 318i/is/Ti | E36 | M42/B18 DISA2 | 1/95--> | 0 261 203 282 | Bosch Motronic M1.7.2 w/ EWS-II |
| 318i/is/Ti | E36 | M42/B18 DISA2 | 1/95--> | 0 261 203 357 | Bosch Motronic M1.7.2 w/ EWS-II |
| 318i/is/Ti | E36 | M44/B19 | 96--> | 0 261 203 667 | Bosch Motronic M5.2 (OBD-II) |
| Z3 | E36 | 1.8L 8V (M44/B18) | 96--> | Bosch Motronic M1.7.3 | |
| Z3 | E36 | M44/B19 | 96--> | 0 261 203 667 | Bosch Motronic M5.2 (OBD-II) |
| 320i | E30 | M20/B20 (129hp) | 87-91 | 0 261 200 152 | Bosch Motronic M1.1 |
| 320i | E30 | M20/B20 (129hp) | 87-91 | 0 261 200 172 | Bosch Motronic M1.3 |
| 320iS | E30 | S14/B20 (192hp) | 87-89 | 0 261 200 087 | Bosch Motronic ML3.1 |
| 325e/es | E30 | M20/B27 (122hp) | 9/84-12/86 | 0 261 200 027 | Bosch Motronic Basic M1.0 |
| 325e/es | E30 | M20/B27 (127hp) | 1/87-9/87 | 0 261 200 154 | Bosch Motronic M1.1 |
| 325i/ECE | E30 | M20/B25 (171hp) | 85-87 | 0 261 200 081 | Bosch Motronic M1.0 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 153 | Bosch Motronic M1.1 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 173 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 351 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 380 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 382 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 524 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 525 | Bosch Motronic M1.3 |
| 325i/is/iX | E30 | M20/B25 (170hp) | 87-91 | 0 261 200 526 | Bosch Motronic M1.3 |
| M3 | E30 | S14/B23 (195hp) | 86-08/89 | 0 261 200 071 | Bosch Motronic M1.0 Motorsport |
| M3 | E30 | S14/B23 (215hp) | 09/89-90 | 0 261 200 091 | Bosch Motronic M1.0 Motorsport |
| M3 - Evo2 | E30 | S14/B23 (220hp) | 88 | 0 261 200 090 | Bosch Motronic M1.0 Motorsport |
| M3 - Evo3 | E30 | S14/B25 (238hp) | 01/90-05/90 | 0 261 200 092 | Bosch Motronic M1.0 Motorsport |
| 325i/is | E36 | M50/B25 | thru 8/91 | 0 261 200 403 | Bosch Motronic M3.1 |
| 325i/is | E36 | M50/B25 | 9/91-8/92 | 0 261 200 402 | Bosch Motronic M3.1 |
| 325i/is/ic | E36 | M50tu/B25 | 9/92-12/94 | 0 261 200 413 | Bosch Motronic M3.3.1 |
| 325i/is/ic | E36 | M50tu/B25 | 1/95--> | 0 261 200 413 | Bosch Motronic M3.3.1 w/ EWS-II |
| 328i | E36 | M52/B28 | 96--> | Bosch Motronic MS41.1 (OBD-II) | |
| M3 - Euro | E36 | S50/B30 | 93-95 | 0 261 203 075 | Bosch Motronic M3.3 |
| M3 | E36 | S50us/B30 | thru 12/94 | 0 261 203 506 | Bosch Motronic M3.3.1 |
| M3 | E36 | S50us/B30 | 1/95--> | 0 261 200 413 | Bosch Motronic M3.3.1 w/ EWS-II |
| M3 | E36 | S50us/B32 | 96--> | Bosch Motronic MS41.1 (OBD-II) | |
| 520i | E34 | M20/B20 (129hp) | 87-90 | 0 261 200 172 | Bosch Motronic M1.3 |
| 525i | E34 | M20/B25 | 87-90 | 0 261 200 173 | Bosch Motronic M1.3 |
| 525i | E34 | M20/B25 | 87-90 | 0 261 200 524 | Bosch Motronic M1.3 |
| 525i | E34 | M50/B25 | thru 8/91 | 0 261 200 405 | Bosch Motronic M3.1 |
| 525i/iT | E34 | M50/B25 | 9/91-1/92 | 0 261 200 403 | Bosch Motronic M3.1 |
| 525i/iT | E34 | M50/B25 | 2/92-93 | 0 261 200 402 | Bosch Motronic M3.1 |
| 525i/iT | E34 | M50tu/B25 | 93-12/94 | 0 261 200 413 | Bosch Motronic M3.3.1 |
| 525i/iT | E34 | M50tu/B25 | 1/95--> | 0 261 200 413 | Bosch Motronic M3.3.1 w/ EWS-II |
| 528i | E39 | M52/B28 | 96--> | Bosch Motronic MS41.1 (OBD-II) | |
| 533i | E28 | M30/B32 | 84 | 0 261 200 008 | Bosch Motronic M1.0 Basic |
| 528e | E28 | M20/B27 | 9/84-12/86 | 0 261 200 027 | Bosch Motronic M1.0 Basic |
| 528e | E28 | M20/B27 | 01/87-09/87 | 0 261 200 154 | Bosch Motronic M1.1 |
| 535i/is | E28 | M30/B34 | 85-87 | 0 261 200 059 | Bosch Motronic M1.0 Adaptive (24 pin) |
| 535i/is | E28 | M30/B34 | 88 | 0 261 200 059 | Bosch Motronic M1.0 Adaptive (28 pin) |
| 535i/is | E28 | M30/B34 (218hp) | 85-87 | 0 261 200 061 | Bosch Motronic M1.0 |
| 535i | E34 | M30/B35 | 89-92 | 0 261 200 179 | Bosch Motronic M1.3 |
| 530i | E34 | M60/B30 | 3/93-8/94 | 0 261 200 404 | Bosch Motronic M3.3 |
| 530i | E34 | M60/B30 | 9/94-12/94 | 0 261 200 404 | Bosch Motronic M3.3 w/ air pump |
| 530i | E34 | M60/B30 | 1/95-4/94 | 0 261 203 484 | Bosch Motronic M3.3 w/ EWS-II |
| 540i | E34 | M60/B40 | thru 12/94 | 0 261 200 404 | Bosch Motronic M3.3 |
| 540i | E34 | M60/B40 | 1/95--> | 0 261 203 484 | Bosch Motronic M3.3 w/ EWS-II |
| 540i | E39 | M62/B44 | 96--> | 0 261 203 474 | Bosch Motronic M5.2 (OBD-II) |
| M5/M635CSI | E28/E24 | S38/B35 (260hp kat) | 87-88 | 0 261 200 079 | Bosch Motronic M1.0 Motorsport |
| M5/M635CSI | E28/E24 | M88 (286hp) | 84-87 | 0 261 200 055 | Bosch Motronic M1.0 Motorsport |
| M5 | E34 | S38/B36 (315hp) | 91--> | 0 261 200 350 | Bosch Motronic M1.2 |
| 633csi | E24 | M30/B32 | 84 | 0 261 200 008 | Bosch Motronic M1.0 Basic |
| 635csi | E24 | M30/B34 | 85-87 | 0 261 200 059 | Bosch Motronic M1.0 Adaptive |
| 635csi | E24 | M30/B35 | 86-88 | 0 261 200 150 | Bosch Motronic M1.1 |
| 635csi | E24 | M30/B35 | 89 | 0 261 200 179 | Bosch Motronic M1.3 |
| 730i | E32 | M30/B30 | 89-92 | 0 261 200 178 | Bosch Motronic M1.3 |
| 733i | E23 | M30/B32 | 84 | 0 261 200 008 | Bosch Motronic M1.0 Basic |
| 735i | E23 | M30/B35 | 09/80-09/82 | 0 261 200 001 | Bosch Motronic M1.0 Basic |
| 735i | E23 | M30/B34 (218hp) | 84-87 | 0 261 200 011 | Bosch Motronic M1.0 Adaptive |
| 735i | E23 | M30/B34 | 84-87 | 0 261 200 059 | Bosch Motronic M1.0 Adaptive |
| 735i/iL | E32 | M30/B35 | 86-88 | 0 261 200 150 | Bosch Motronic M1.1 |
| 735i/iL | E32 | M30/B35 (211hp) | 89-92 | 0 261 200 179 | Bosch Motronic M1.3 |
| 740i/iL | E32 | M60/B40 | 9/92-4/94 | 0 261 200 404 | Bosch Motronic M3.3 |
| 740i/iL | E38 | M60/B40 | 1/95--> | 0 261 203 484 | Bosch Motronic M3.3 w/ EWS-II |
| 740i/IL | E38 | M62/B44 | 96--> | 0 261 203 474 | Bosch Motronic M5.2 (OBD-II) |
| 745i | E23 | M102/B34 (252hp) | 83--86> | 0 261 200 013 | Bosch Motronic M1.0 |
| 750iL | E32 | M70/B50 | 88-90 | 0 261 200 156 | Bosch Motronic M1.2 |
| 750iL | E32 | M70/B50 | 91--> | 0 261 200 352 | Bosch Motronic M1.7 |
| 750iL | E38 | M73/B54 | 9/94--> | 0 261 203 473 | Bosch Motronic M5.2 (OBD-II) |
| 840i | E31 | M60/B40 | 9/93-12/94 | 0 261 200 404 | Bosch Motronic M3.3 |
| 840i | E31 | M60/B40 | 1/95--> | 0 261 203 484 | Bosch Motronic M3.3 w/ EWS-II |
| 840i | E31 | M62/B44 | 96--> | 0 261 203 474 | Bosch Motronic M5.2 (OBD-II) |
| 850i | E31 | M70/B50 | 91--> | 0 261 200 352 | Bosch Motronic M1.7 |
| 535i/ | E28 | M30/B34 (245hp) | 85-87 | 0 261 200 011 | M1.0 |
| Alpina B7 | E24 | M30 (300hp) | 85-87 | 0 261 200 043 | M1.0 |
| Alpina B7 | E24 | M30 (330hp) | 85-87 | 0 261 200 043 | M1.0 |
| Alpina B7 Turbo Kat. | E24 | M30 (320hp) | 85-87 | 0 261 200 079 | M1.0 |
| Alpina B10 Biturbo | E34 | M30 (360hp) | 89-94 | 0 261 200 079 | M1.1 |
In addition, you may want to check out this list of complete Bosch part numbers which correspond to the version of Motronic inside the unit. This list is very handy to take with you to the junk yard to try to find a DME with a part number on it that matches the one in your car.
Well, there you have it - it's really not too difficult at all. If you would like to see more technical articles like this one, please continue to support Pelican Parts with all your parts needs. If you like what you see here, then please visit our online BMW catalog and help support the collection and creating of new and informative technical articles like this one. Your continued support directly affects the expansion and existence of this site and technical articles like this one. As always, if you have any questions or comments about this helpful article, please drop us a line.
Source: https://www.pelicanparts.com/BMW/techarticles/E36-DME-Repair/E36-DME-Repair.htm
Posted by: stonefieldbeulah496.blogspot.com
