2021 ram 3500 tail lights not working

[RomeoGroup]

Hey guys wondering if anyone can help,
Just started this morning and noticed my taillights don’t work. Break lights work, blinkers work, all the lights work except the running taillight. Any ideas?

 

[djevox]

Did you check bulbs if halogen? From your post, we don’t know if you have led or not.

 

[RomeoGroup]

Did you check bulbs if halogen? From your post, we don’t know if you have led or not.

Yes they are not led. Bulbs look fine. They light up when I press the brake

 

[djevox]

Yes they are not led. Bulbs look fine. They light up when I press the break

Ok, I doubt both running light fillaments would be bad unless you have a wiring issue that caused them to blow. What’s the year and the trim level, and do you have a test light or multimeter?

 

[RomeoGroup]

Ok, I doubt both running light fillaments would be bad unless you have a wiring issue that caused them to blow. What’s the year and the trim level, and do you have a test light or multimeter?

It’s a 2021 3500 Big Horn. I do have a test light with me.

 

[djevox]

It’s a 2021 3500 Big Horn. I do have a test light with me.

Ok, I’ll look up the wiring for you in a few minutes. Is this out of warranty already?

 

[RomeoGroup]

Ok, I’ll look up the wiring for you in a few minutes. Is this out of warranty already?

Yea unfortunately

 

[djevox]

Yea unfortunately

Is this a chassis cab?

 

[RomeoGroup]

Is this a chassis cab?

Crew cab

 

[djevox]

Crew cab

Thanks, looking now

 

[djevox]

Edit: it's important to use a scan tool to see what codes are stored in the BCM. This really should be the first step.

Tailights still have a circuit board, so there's a couple options:
1) Remove bulbs and run 12v to the each running lamp bulb to see if the bulb's bad (assuming you've already visually inspected the correct bulbs) as a confirmation to what you inspected.
2) use a testlight to see if 12v+ is being output in the bulb socket. This also has the added bonus of confirming the circuit board and wiring is good. You need to be very careful with this, especially since there's a circuit board involved. If you short the socket to ground, you may fry the board.
3) if you feel uncomfortable with #2, check for 12v+ at the input wires before the board (colors below).

As always, positive voltage is only half the equation. You also need to check that ground is good to both tail lights. (More below)

Tailight colors:
running lamp: white/orange
stop lamp: white/green
reverse lamp: white/violet


ground locations:
left taillight: left frame rail
right taillight: right frame rail

 

[bigdodge]

Hey guys wondering if anyone can help,
Just started this morning and noticed my taillights don’t work. Break lights work, blinkers work, all the lights work except the running taillight. Any ideas?

might want to post on the heavy duty forum
they might have more info, or someone there might have had the same issue

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[Debsdamo9]

Hey guys wondering if anyone can help,
Just started this morning and noticed my taillights don’t work. Break lights work, blinkers work, all the lights work except the running taillight. Any ideas?

Same issue here! Any fix yet?

 

[KMach]

I’m only here scrolling because I thought I just had bad luck. I had a taillight out this am on my 21 1500 and bought a pack of bulbs for both sides. As soon as I saw Stanley on the bulbs and not sylvania I knew what the issue was. Even if the filament looks good it’s probably the bulb. I’ve done bulbs rarely at work on stuff with under 12k miles which is clearly a defect, but never bulbs this early at 38,000. Now I know why I see so many rams on the road with one taillight figuring they had to have 80-90k miles.

Was really expecting to chase wires tonight to be honest as they put these grounds in cool places now but got lucky this time. Some may remember the old FCM/IPM days and I took a trip down memory lane!