Driver's side parking lamps will not turn off?

JOHNCBENNETT

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2021 RAM PROMASTER
3.6L
6 CYL
2WD
AUTOMATIC
12,000 MILES

The vehicle listed above is a 3500. Camper van conversion by Thor Industries, designated as a Thor "Sequence 20AT".

I have owned the van for almost two years, no issues. First owner.

The parking lights on the driver's side have come on and will not turn off: The van has been driven regularly, and had been sitting for a few days in our driveway after returning from a multi-day trip. No issues. Last night, we noticed a faint glow from the driver's side, and discovered that both the front and rear parking lights were illuminated. This was not present the night before. We tried starting the van, checking all switches, moving it, but no change. This morning, the lights are still illuminated.

I understand this may be a short in a wiring harness or a bad relay. Any suggestions on where to search or troubleshoot would be very much appreciated. Thank you!

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10 Replies

KEN L

MASTER CERTIFIED MECHANIC
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Yep, this means the BCM is going out. to be sure we should do a CAN scan. You can get a CAN scanner (Controller Area Network) which will work on most cars from Amazon.

Here is a video to show you how:

https://youtu.be/u-4syLc-ifQ

and

https://www.2carpros.com/articles/can-scan-controller-area-network-easy

Here is how to change the BCM out and its location, you can get a preprogrammed unit by searching Google or Ebay.

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Monday, September 11th, 2023 AT 6:38 PM

JOHNCBENNETT

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Hi Ken,

Thank you so much for the quick and detailed reply. I will review and try this, and report back. I spent the day today fiddling with batteries, relays and fuses, so this helps immensely.

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Monday, September 11th, 2023 AT 7:56 PM

KEN L

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You are welcome, please let me know how it goes.

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Tuesday, September 12th, 2023 AT 10:04 AM

JOHNCBENNETT

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Hi Ken,

Thank you again for the advice. I've been fiddling with this all week. I picked up a scanner from Amazon, and it found a few issues. The obvious one was:

BCM (Body Control Module - TIPMCGW/FCMCGW)
B11B0-18
Front / Rear Left Parking Lights and Front Left Side Marker - Circuit Current Below Threshold"

So, the BCM knew about the problem! And even stranger, it reported the following four other faults:

B12C7-15 High Beam Right - Circuit Short To Battery Or Open Active
B12C5-15 High Beam Left - Circuit Short To Battery Or Open Active
B12C3-15 Low Beam Right - Circuit Short To Battery Or Open Active
B12C1-15 Low Beam Left - Circuit Short To Battery Or Open

Do you still think the BCM is going out? Or is it accurately reporting something that it sees occurring in the van?

Further piece of the puzzle: The main display on the dashboard also now states "Parking Lights Out" and "Daytime Running Lights Out". I assume those are messages via codes from the BCM.

Of course, it's a bit backwards. The parking lights aren't *out*. They're the opposite of out :).

If you have any further ideas, I would very much appreciate your feedback. Thank you!
John

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Sunday, September 17th, 2023 AT 7:18 AM

JOHNCBENNETT

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Hi Ken,

Thank you again for the advice. I've been fiddling with this all week. I picked up a scanner from Amazon, and it found a few issues. The obvious one was:

BCM (Body Control Module - TIPMCGW/FCMCGW)
B11B0-18
Front / Rear Left Parking Lights And Front Left Side Marker - Circuit Current Below Threshold"

So, the BCM knew about the problem! And even stranger, it reported the following four other faults:

B12C7-15 High Beam Right - Circuit Short To Battery Or Open Active
B12C5-15 High Beam Left - Circuit Short To Battery Or Open Active
B12C3-15 Low Beam Right - Circuit Short To Battery Or Open Active
B12C1-15 Low Beam Left - Circuit Short To Battery Or Open

Do you still think the BCM is going out? Or is it accurately reporting something that it sees occuring in the van.

Further piece of the puzzle: The main display on the dashboard also now states "Parking Lights Out" and "Daytime Running Lights Out". I assume those are messages via codes from the BCM.

Of course, it's a bit backwards. The parking lights aren't *out*. They're the opposite of out :).

If you have any further ideas, I would very much appreciate your feedback. Thank you!
John

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Sunday, September 17th, 2023 AT 7:18 AM

KEN L

MASTER CERTIFIED MECHANIC
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I should have had you double check all fuses, please go over this guide to help, if all fuses are good the BCM sounds bad.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Check out the images (below). Please let us know what happens.

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Monday, September 18th, 2023 AT 11:03 AM

JOHNCBENNETT

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Hi Ken,

Thanks for this. I will go through the fuses one by one. I am now intimately familiar with the location of the three fuse boxes in the van :).

I will report back.
John

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Tuesday, September 19th, 2023 AT 9:28 AM

KEN L

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Sounds good, please let me know.

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Wednesday, September 20th, 2023 AT 6:02 PM

JOHNCBENNETT

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Ken,

Thank you so much for all your advice. I learned a lot fiddling with this thing!

I've resolved the issue: It turns out it was a faulty trailer harness module that was back feeding power into the lights. I traced the harness wiring to the module and pulled the fuse for it at the battery.

Thanks again for all the advice.
John

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Friday, September 22nd, 2023 AT 2:49 AM

KEN L