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Discussion Starter #1
Last night I noticed that both of my headlights were pointing very low. I've checked everything I can think of and am not finding anything wrong.

-both headlights self-test the auto-leveling when you turn them on (they tilt down, then back up, but not up high enough)
-headlights adjusters are not broken
-both front and rear suspension sensor arms are firmly attached
-connectors were firmly seated and sealed up (no corrosion), unplugged and reconnected them just in case
-both sensors do not appear physically damaged
-no codes stored in LCM or any other modules (checked with INPA and PA Soft)

I even tried disconnecting the battery for a while thinking that might reset them or force them to recalibrate but that did nothing.

I retrofitted a LCM IV a few months ago but it was properly coded and the leveling has been working great since. I replaced my brakes last weekend but didn't touch either sensor and the lights were working fine all day Monday and Tuesday.

At this point I can only assume that one of the sensors has failed internally. Is there an easy way to tell which one it is, or should I just order both? Or is it something else?

Any help is appreciated.
 

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The LCM IV has the headlight leveling sensor builtin while cars with the LCM III had a separate sensor. I believe others have had this same issue where the two sensors seem to cause an issue. A video on Youtube by E39 Source talks about it briefly. The solution would be to swap in an LCM III B as it has all the features of the LCM IV but without the leveling sensor included.

(Watch around the 8:30 mark)
 

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Discussion Starter #4
Are you sure they were aiming correctly all the time? May just need to manually adjust the 'base' setting.
Yeah, pretty sure. They would sweep through the full range upon startup every time. I re-adjusted both headlights (manually) when I repaired the adjusters a couple of years ago. This was before I had the LCM IV.

The LCM IV has the headlight leveling sensor builtin while cars with the LCM III had a separate sensor. I believe others have had this same issue where the two sensors seem to cause an issue. A video on Youtube by E39 Source talks about it briefly. The solution would be to swap in an LCM III B as it has all the features of the LCM IV but without the leveling sensor included.

(Watch around the 8:30 mark)
So, my car came with an LCM III B from the factory. I did watch that video and was of the LWR module before retrofitting the LCM IV.. I used an LCM IV from a late model E39 w/ auto_LWR and recoded it to factory defaults using NCS Expert. I think Ryan could have made it work if he had done this after using PA Soft to write the VIN and mileage. I would think if the LCM and LWR modules were sending conflicting messages that the auto-leveling just wouldn't function at all. I could be wrong though.
 

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Just wondering why you changed the LCM III B to an LCM IV? What benefit did it have or was your LCM III B no longer working?
 

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Discussion Starter #6
Just wondering why you changed the LCM III B to an LCM IV? What benefit did it have or was your LCM III B no longer working?
It was still working fine. I mainly just wanted to retrofit it so that I would have the ability to turn off cold checks of the halos and license plate lights and have the ability to adjust PWM values.
 

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I was unaware there were any differences between the 2 except for the integration of the LWR. The next logical step is checking the sensors. Does the system rely on all sensors to work properly or can you unplug one at a time to determine which one is malfunctioning?
 

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Discussion Starter #8
It definitely relies on both of them working in order to properly level the lights, however, I'm thinking that if one of them is faulty then the LCM/LWR puts it in a failsafe mode and aims the lights down low so as not to blind oncoming traffic (since it doesn't know if the car is level). To answer your question, I don't think unplugging one of them will help isolate the bad sensor. I can try it though.
 

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The LCM IV has the headlight leveling sensor builtin while cars with the LCM III had a separate sensor. I believe others have had this same issue where the two sensors seem to cause an issue. A video on Youtube by E39 Source talks about it briefly. The solution would be to swap in an LCM III B as it has all the features of the LCM IV but without the leveling sensor included.

(Watch around the 8:30 mark)
I'd take those E39 source videos with a grain of salt. Having watched a couple of them, they really don't know much about how the electronics work. The reason their LWR didn't work is because the LCM wasn't coded for the car. If you code it for your car with NCS Expert, it will set everything in the module appropriately. For LWR specifically, pre-2003 cars need "LWR_AUT_EXTERN" to be set to aktiv.

LCM III cars use a separate module, and that module still works fine with an LCMIV - the LCMIV's internal circuitry just won't be used (and you can therefore use a non-LWR LCM IV on pre-2003 E39s). 2003 E39s came with LCMIVs and have the sensors and motors wired directly to the LCM instead of the separate module - those do require an LCMIV with LWR built in).

It definitely relies on both of them working in order to properly level the lights, however, I'm thinking that if one of them is faulty then the LCM/LWR puts it in a failsafe mode and aims the lights down low so as not to blind oncoming traffic (since it doesn't know if the car is level). To answer your question, I don't think unplugging one of them will help isolate the bad sensor. I can try it though.
You should be able to read the sensor data in INPA. I think your headlights (or at least parking lights) need to be on to be able to read the LWR module.
 

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Discussion Starter #10
I'd take those E39 source videos with a grain of salt. Having watched a couple of them, they really don't know much about how the electronics work.

LCM III cars use a separate module, and that module still works fine with an LCMIV - the LCMIV's internal circuitry just won't be used (and you can therefore use a non-LWR LCM IV on pre-2003 E39s). 2003 E39s came with LCMIVs and have the sensors and motors wired directly to the LCM instead of the separate module - those do require an LCMIV with LWR built in).

You should be able to read the sensor data in INPA. I think your headlights (or at least parking lights) need to be on to be able to read the LWR module.
I did not realize that the pre-03 E39 still uses the LWR when an LCMIV has been retrofitted. I thought that the LCMIV assumed control of the headlight leveling. I guess I stand corrected. Also didn't know I had to have the lights switched on to be able to read the LWR module. So, I just went out to the garage and tried scanning the LWR again with the switch turned to the parking light position. Here's what I found.

934528


Translated... "Sensor error in front. Outside temperature 8 deg C. Error currently not available."

I also checked the status of the sensors.

934527



So, does this mean that the front sensor isn't getting power? Or just that it is faulty in general? The wiring leading up to it looked fine, no damage.

Just for the record, I have an LCMIV w/ auto LWR. This one, to be specific.

 

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So it is pointing to an error for the front sensor, but it does also say "error currently not present" so I don't know for sure if that's your problem. Could be that it just hasn't detected it as a problem yet since you haven't been driving and the module doesn't have enough data for a plausibility check. Power supply does sound like it could be the actual power supply, but it could be a bad translation for the sensor voltage. Either way it does seem like something is off there.

And yeah, in a pre-03 E39, the LCM won't be used for the LWR control even if you retrofit an LCMIV. You can move the wires from the LWR module to the LCM, but you'd probably have to extend the wires or build some sort of adapter.
 

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Discussion Starter #12
When I clear the code and cycle the lights on/off it comes back. Also cleared it and went for a drive (with the lights on), then rechecked when I got back. Same code.

Yeah I'm not really sure what the "power supply" voltage means. I may be able to check the voltage at the connector that plugs into it, if I can get my multimeter on the pins somehow.
 

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Discussion Starter #13
New front sensor did the trick. I can see again!

Cleared the code in INPA and checked the voltages again. Front sensor looks good. Wondering if I ought to pick up a rear sensor too, seeing as it's outside of the green range. Maybe the rear is nearing failure as well?

934688
 
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