Error Free e36 Licence Plate LEDs

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Last year I bought several “Canbus Error Free” license plate LEDS trying to find some that would not actually generate an error on the OBC of my 1998 BMW e36 M3. I’ve since learned that canbus means nothing in this context. I even bought the top dollar, guaranteed error free lights from JLeviSW which are the same as sold by BavAuto. And while those lights worked for a few weeks error-free eventually they too generated an failure message.

I did some research and found a DIY that recommended soldering a 0.47 ohm 10W resistor across the contacts in the OEM light housing to reduce the current across the circuit enough to fool the OBC into thinking that there was a normal, functioning bulb. I’d even read about soldering a bulb somewhere into the circuit which would work but sounds like a kludge at best.

Above: Expensive and supposedly error free e36 license plate LEDS.

BMW e36 M3 Lic Plate Light Fail warning on OBC

What I wanted was a snap-in solution that would not permanently alter any of my wiring or parts. I also wanted it to work with my expensive lights. But no such circuit existed. So I researched, trawling through RealOEM, website and forums to find the parts required to make a true, snap-in error canceling circuit.

This is the result:
BMW e36 License Plate LED Error Canceling Circuit

Above: Home made license plate light failure error canceling circuit.

Parts List


Red and Black 18g Wire
Heat Shrink Tubing
2x BMW 8 Connector, Male 61-13-1-378-149 $2.50 each
2x BMW Pin Conn. Blk, Female 61-13-1-378-106 $1.50 each
2x Circular Contact with Cable, 0.5-1.5mm 61-13-1-376-191 $1.50 each
2x Cable Socket, Round, Female 61-13-1-376-202 $1.50 each
2x 0.47 Ohm 10W Resistors $0.45 each
Optional 6x Heat Sinks
Optional 1x Thermal Adhesive
OR
2x Green 10 Watt 47 Ohm 5% Aluminum Shell Wire Wound Resistor $5.30 each

Total cost if you use the green resistors is $19.30 each. This is not a cheap project.

Note: You will notice that I list two different styles of resistor. The green resistor has a built-in heat sink which I didn’t use but would negate the need for gluing on heat sinks. Remember, this circuit will generate as much heat as a light bulb so consider placement carefully.

Tools


Solder
Soldering Iron
Wire Strippers

Steps


Before you proceed you must read and accept the disclaimer and warning at the top of this article and know that you proceed at your own risk. I am not responsible for anything that happens and I’m not an electronics expert. If you mess this up you could start a fire, electrocute yourself or any number of other calamities. I’m not advising anyone to do this, this is not a DIY project.

Essentially, I’m going to insert the resistor into the license plate light circuit making sure that the resistor is in series with the circuit. This is a little tricky with such a large resistor but possible.

  1. Prepare the wire. Each circuit needs 2x red and 2x black wires. Cut them about 12″ long and shorten them to the correct length later on.
  2. Take two of the black wires and strip 1/2″ off one end of each wire.
  3. Solder both black wires together and around 1 of the resistor terminals. Cover this connection entirely in heat shrink. Failure to do so may result in a short circuit or worse.
  4. Take two of the red wires and strip 1/2″ off one end of each wire.
  5. Solder both red wires together and around the remaining free resistor terminal. Cover this connection entirely in heat shrink.
  6. Both black wires are soldered to one side of the resistor and both red wires soldered to the other.
  7. Trim the wires so that they are all even in length. It may be helpful to heat shrink the bundle together as is illustrated above. Then trim off 1/2″ of insulation from each end.
  8. Now to one red and one black wire solder one female (ring) connector 61-13-1-376-202 to each.
  9. To the remaining red and black wires solder one male (tip) connector 61-13-1-376-191 to each.
  10. Insert the wires into the plug housings. The black (ground) wire should be inserted into the keyed side of the plug housing, that is the side with the extra bit of plastic that sticks out. See the photo below and note the brown (ground) wire in relation to the shape of the plug.

IMG_8253

Now with the car turned off connect the new circuit to the license plate light wiring and see if an error is generated. No error should be generated. Everything goes into the trunk cavity through the holes for the license plate housing.

BMW e36 License Plate LED Error Canceling Circuit

The following page was very useful to my in researching this project: http://www.unofficialbmw.com/all/electrical/all_contact_pins.html

Update:


a month or so after I made ‘version 1’ of this error cancelling circuit the failed light message appeared on the OBC of my M3. Inspection revealed that one of the wires on a resistor had broken off where I had bent it sharply. The resistors I used are clearly meant for circuit board applications and not in the manner that I am used it.

I clipped the expensive plugs off to reuse and soldered in one of the green resistors that I sourced earlier. The result seems more robust and compact.

bmw e36 license plate LED error cancelling circuit

October 31, 2014 cosmetic, e36 m3