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E36 M3 (1992-1999) {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999


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Old Mon, Sep-04-2017, 04:23:49 PM   #1
LockDots
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Default Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

This DIY has been made in the past but due to Photobucket killing the hosted images I figured I'd upload a new one.

The "Low Beam Failure" on the OBC can caused by many things such as a blown bulb, dirty socket, broken/damaged wiring, etc. The most common cause of this seems to be switching to HID headlights.

First, I'll explain how/why this failure occurs. If you have a CCM (Check Control Module) the headlights are monitored for changes in current. When you turn your headlights on a certain amount of current passes from the battery, to the relay, to the CCM, to the headlights, and finally to ground to return to the battery. What the CCM does is monitor the current being drawn by the headlights (individually). If it senses that too much or too little current is being drawn it assumes that a bulb is out and throws a code on the OBC that we've all come to learn to love.

When an HID system is installed (with or without a relay harness) the OBC is tricked into thinking a bulb is not present or working. Remember: the CCM was designed to monitor the current being drawn from the a Halogen/Incandescent bulb, not an HID ballast and bulb which draw not only different amounts of current but in a different fashion as well. Hence, the Low Beam Failure warning even though the system (which this vehicle was not designed for) may be functioning just fine.


Currently there are two ways to bypass/prevent this failure warning. Software and Hardware.

The software approach is the easiest in terms of labor and reversibility. I won't be going into this method for two reasons.
1 - This writeup is meant to outline how to do it the "hardware way".
2 - You lose the check control function overall. You no longer get warning messages for headlights, tail lights, brake lights, license plate lights, coolant level, and washer fluid level.

If you decide that you want to go with the software method, it can be found here: Disabling The OBC

Since I didn't want to lose all of those monitors I decided to go the hardware route and disable only what I wanted to - the lowbeam check.

The hardware approach is comprised of literally bypassing the CCM by removing the monitored wires from the CCM plug and joining them together (on the harness running to the CCM, not the plug/CCM side). What this does is complete the circuit so power still reaches the lights without the CCM in the path.

Below is a portion of the ETM (Electronics Troubleshooting Manual) which covers the following models: 1997 318is/c, 328i/c, & M3. The only reason I reference this is because I have a 97 M3 and so, it was the manual I have. However this should be true for most if not all E36s with a CCM.



According the schematic, the CCM's input for the Left Low Beam is a Yellow/Gray wire and the output is a Yellow/Green wire. The CCM's input for the Right Low Beam is a Yellow/Red wire and the output is a Yellow/Blue wire. What you do is simply cut the four wires at the CCM's White Connector, then join the Yellow/Gray to Yellow/Green and the Yellow/Red to Yellow/Blue. I suggest leaving some slack on the connector side of the wires should you decided to reverse this in the future.

The following are pictures I took during my process.

First and foremost, disconnect the battery. It doesn't have to be completely disconnected but at the bare minimum disconnect the negative/ground lead.

The module is found underneath the left side in the corner where the firewall meets the kick panel. You'll see the CCM's connectors facing the right side, with a white connector and a black one.



Towards the back of the CCM (facing the rear of the car) there will be a plastic 10mm nut that can be removed with a 10mm socket or by hand. They're really not that tight but getting to them is a little cumbersome if you have large hands.



Once you remove this nut you'll be able to pull it down a bit to release this tab from the mounting post and slide it towards the rear to disengage the other side of the CCM. The other side is slotted so you don't necessarily have to remove the rear nut. The following two pictures are so you can see what you're working with since you're working blind/by feel a bit.

Rear:



Front:



Once free you can pull it to the right side to free it completely. You'll have to wrestle it around a bit around the thick wire harness a bit to free it.



As you can see, there's not much room to work with the wiring here.



Disconnect the module (you remembered to disconnect the battery, right?).

Here's the part that makes this so much easier to do by creating extra slack in the harness. If you look at the two thick harnesses, you'll see the CCM's white connector harness looping through the middle of the two.



Spread the two thicker harnesses apart and feed the CCM's white connector harness through them. This should give you an extra few inches to work with as well as bringing it towards you so you don't have to work underneath the dash or upside down.



This is the harness you'll be working with. Notice that the two inputs and two outputs are grouped together.



Next, cut and join the wires as mentioned previously. The method of how you join them doesn't really matter so long as it's secure. I chose to use crimp caps since the wires were all facing the same direction. I left about 2-3 inches of wire on the CCM-side of the connector in case I ever want to undo this.





Make sure you tape up any wires you're not using and either tape or wire-tie the harness back together to keep it from getting any messier than BMW already left it for us



Install is the reverse of removal . Feed the white connector harness back through the two larger harnesses, connect the CCM to the black and white connectors, slide the front tab into place between, push the rear of the CCM back into place, and screw or push the nut back on.



Now reassemble your dash, connect your battery and give it a shot. The same can be done for any of the other lights that the CCM monitors. You just have to check the ETM to see which wire colors you need.

Hope this helps, and I hope to keep these pictures hosted on Flickr for a long time.

Take care!
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Old Mon, Sep-04-2017, 05:12:18 PM   #2
M_Parallel
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

Since we have old cars, I thought the it just checked for open or closed curcuit. Bulb goes out, filament burned through, open circuit, OBC message.
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Old Mon, Sep-04-2017, 05:34:19 PM   #3
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

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Originally Posted by M_Parallel View Post
Since we have old cars, I thought the it just checked for open or closed curcuit. Bulb goes out, filament burned through, open circuit, OBC message.
I thought this as well until I opened up the OBC. It looks like the circuitry is comparing voltage and/or current to a given/reference source. Also, if the case was simply checking for an open/closed circuit the HID ballasts shouldn't affect that since they're still sourcing current, albeit in a different manner compared to incandescent bulbs.

That being said, the way it sources current could be tricking the CCM into thinking it's an open circuit. I don't know for sure without looking at the code or a true schematic for the CCM.
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Old Mon, Sep-04-2017, 06:11:51 PM   #4
M_Parallel
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

I thought HID gave the error because they have no filament, so always open circuit.
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Old Mon, Sep-04-2017, 06:18:49 PM   #5
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

It's certainly possible, but the only way for electronics (especially in the case of solid state) to know if there's an open circuit or not is to check for moving current or voltage on both ends (input and output) to be present.
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Old Mon, Sep-04-2017, 07:09:50 PM   #6
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

I mentioned why in the post. I don't want to disable the check control entirely.
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Old Mon, Sep-04-2017, 07:13:22 PM   #7
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

Yeah read that wrong.
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Old Mon, Sep-04-2017, 07:26:55 PM   #8
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

Quote:
Originally Posted by LockDots View Post
I mentioned why in the post. I don't want to disable the check control entirely.
Me neither. So I'm happily running old school H7 bulbs. Does the job, no false positives.
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Old Mon, Sep-04-2017, 07:36:11 PM   #9
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

I have a retrofit so I can easily tell when one of my bulbs are out. I also have a relay harness for the ballasts which gives me the low beam failure so this was a perfect fix for me.
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Old Tue, Sep-05-2017, 06:20:46 AM   #10
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Default Re: Bypassing the CCM to avoid "Low Beam Failure" message on OBC.

Quote:
Originally Posted by M_Parallel View Post
Since we have old cars, I thought the it just checked for open or closed curcuit. Bulb goes out, filament burned through, open circuit, OBC message.
That started already with the E32 7 1988-1994 series (in Europe even from around mid 1986), hot and cold checking of bulbs. So even when lights are not switched on and something is wrong with the bulbs or other things, check control warning comes on.
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Discussing Bypassing the CCM to avoid "Low Beam Failure" message on OBC. in the E36 M3 (1992-1999) Forum - {Euro - S50 B32 321hp @ 7400 rpm} {U.S. - S52 B32 240 hp @ 6000 rpm}
Total Produced: 71,212 - Years Produced: 1992 to 1999 at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)