Electrical problem with my CLC

[txtinman]

I've got a problem with my '03 CLC that has myself and the folks at Chromeheads.org stumped. I'm hoping someone here might have an Idea for me.

As I was entering the interstate and shifting into 5th gear the right jug quit firing and the tach stopped working. I thought the coil went bad so I replaced it. That did not fix the problem. I tested all coils and plugs on the left side and they work there, but not on the right side. I pulled all fuses and checked them with a meter. They were all good. I haven't found any loose connections or shorted wires.

Any ideas?


Lone Star BMW found a broken ground wire that I missed somehow. It was routed poorly according to the mechanic and they did the repair at no charge to me even though the bike was out of warranty. Kudos to a great bunch of guys at Lone Star BMW. I can finally ride again after a month off. :groovy

[cjack]

I've got a problem with my '03 CLC that has myself and the folks at Chromeheads.org stumped. I'm hoping someone here might have an Idea for me.

As I was entering the interstate and shifting into 5th gear the right jug quit firing and the tach stopped working. I thought the coil went bad so I replaced it. That did not fix the problem. I tested all coils and plugs on the left side and they work there, but not on the right side. I pulled all fuses and checked them with a meter. They were all good. I haven't found any loose connections or shorted wires.

Any ideas?

Either a wiring problem to/from the motronic or the motronic.

[txtinman]

Either a wiring problem to/from the motronic or the motronic.
Is the motronic repairable? I've seen a few for sale at Beemer Bone Yard. I wonder if a used one can be trusted?

[cjack]

Is the motronic repairable? I've seen a few for sale at Beemer Bone Yard. I wonder if a used one can be trusted?

Probably not repairable...maybe if a driver is bad you could identify it and change it out.
But check the wiring from the motronic plug to the coil. Disconnect the plug from the motronic and measure from the coil output pin on the motronic plug to the wire end that is plugged onto the coil but you have now disconnected.
That would be pin #33 to the coil terminal marked K1 on the right side coil. The wire coming from #32 is black/green and the wire color coming from #33 is black/violet.
The right side is #33 I think. I believe that is cyl #2 as marked on the schematic.
The #32 pin is marked to go to cyl #1 and I believe that is the left side.
You can also check for power to the coils, +12 volts should be always available on coil terminals marked 15 with the ign key on. The wires going to terminal 15 on the coils are green.
Be careful not to bend or damage the pins in the motronic plug when checking with the ohm meter.

[txtinman]

Cjack,
If the wire from the motronic to the coil checks good, would that indicate the motronic itself is bad? The drivers you mentioned, is that a software thing?

[cjack]

Cjack,
If the wire from the motronic to the coil checks good, would that indicate the motronic itself is bad? The drivers you mentioned, is that a software thing?

If there is +12 on the other side of the coil, I would say so. The driver would be a semiconductor FET or some such. I have no idea what they use for drivers but would guess a power FET.

Also, I see that pin #32 is also the output for the tach signal input. So that may indicate that the wire to the right coil is from pin #32 since your tach signal is dead and I have the coils mixed up left and right. But, you can check my guess that by measuring both sides...32 to one coil and 33 to the other.
I don't know if the tach signal comes right from the motronic plug or somewhere down the wire from the pin #32.

If you don't find any problems with the wiring to the coils, you might want to look for memory faults on the motronic with the dealer's GT-1 before you replace anything.

[txtinman]

I got a CD in the mail today that has a CLC training manual on it as well as wiring diagrams. One illustration shows the Motronic plug with pin 33 connected to cylinder #2, and pin 35 connected to cylinder #1. A wiring diagram shows pin 32 connedted to #1 cylinder. I checked the bike and found pin 35 connected to the right cylinder. I'm assuming cylinder #1 is the right side. The diagram I have also shows the tach connected to pin 32. I'm not sure how to check that. Anyway, I have continuity to both coils from the motronic plug. Where do you think I should check for proper voltage to the plug?

[cjack]

I got a CD in the mail today that has a CLC training manual on it as well as wiring diagrams. One illustration shows the Motronic plug with pin 33 connected to cylinder #2, and pin 35 connected to cylinder #1. A wiring diagram shows pin 32 connedted to #1 cylinder. I checked the bike and found pin 35 connected to the right cylinder. I'm assuming cylinder #1 is the right side. The diagram I have also shows the tach connected to pin 32. I'm not sure how to check that. Anyway, I have continuity to both coils from the motronic plug. Where do you think I should check for proper voltage to the plug?

Confusing about the pin 35 and pin 32. But check the terminal on the coil marked 15. That is the green wire which is +12 volts when the ign key is turned on.
My diagram (on a new wiring diagram cd from BMW) doesn't have a 35 on the motronic. It's possible that the motronic has pins 32 and 35 tied together internally.

[txtinman]

I checked for power at the coil. I'm getting 11 volts at both right and left coils. I guess my battery is a bit low. You mentiond checking for memory faults at the dealer. If there are faults, is that something that can be fixed without replacing the motronic? I already have a date with the dealer, but if I can fix it myself it would save me a lot of money.

[cjack]

I checked for power at the coil. I'm getting 11 volts at both right and left coils. I guess my battery is a bit low. You mentiond checking for memory faults at the dealer. If there are faults, is that something that can be fixed without replacing the motronic? I already have a date with the dealer, but if I can fix it myself it would save me a lot of money.

Well the faults may tell you what is wrong if it is something we haven't thought of. Or it may tell you the motronic needs to be replaced. There may be a way of reading out the faults without the dealer's computer, but I don't know of it. You may want to look around on the IBMWR site

http://www.ibmwr.org/

and see if there is any help there. At the moment it seems like your motronic is not driving the coil on that side. That may be due to a lack of a signal from the hall sender (I don't know how that functions as to the firing of each coil) or some fault inside the motronic. There were some articles I thought in the IBMWR site or maybe elsewhere describing how to check the hall sender signals. Anyway, start with that site and maybe email some of the authors on related articles. If I get knowlegeable on it depending on what I'm doing the next day or two, I'll repost.

[txtinman]

Thanks Jack. I've been talking with Pokie on Chromeheads.org also. We suspected the hall sensor, but his research shows that the sensor would either fire both coils or none at all. I'll check in with IBMWR as well. Thanks a lot for your help.