Hey everyone,
I’m having an issue with the trailer turn signal on my 2020 RAM DT (1500).
When no trailer is connected, all vehicle lights work perfectly.
With a trailer connected, it started a while ago with the truck randomly detecting the left trailer turn signal while driving, even when I was not using the turn signal. This happened very sporadically and the left trailer blinker was still working at that time.
Now the problem has gotten worse:
The left trailer turn signal no longer works at all, and I get constant warning messages in the instrument cluster about the left trailer turn signal — even when I’m not blinking. Sometimes the warning appears every few seconds, sometimes continuously for several minutes.
Here’s what I’ve checked so far:
At this point I’m a bit stuck.
Does anyone know how the trailer lighting is actually controlled on the RAM DT (BCM vs separate trailer module)?
Or has anyone experienced a similar issue with a dead left trailer turn signal output?
Any input would be greatly appreciated. Thanks!
I’m having an issue with the trailer turn signal on my 2020 RAM DT (1500).
When no trailer is connected, all vehicle lights work perfectly.
With a trailer connected, it started a while ago with the truck randomly detecting the left trailer turn signal while driving, even when I was not using the turn signal. This happened very sporadically and the left trailer blinker was still working at that time.
Now the problem has gotten worse:
The left trailer turn signal no longer works at all, and I get constant warning messages in the instrument cluster about the left trailer turn signal — even when I’m not blinking. Sometimes the warning appears every few seconds, sometimes continuously for several minutes.
Here’s what I’ve checked so far:
- Measured directly at the factory US 7-pin trailer connector:
- Right turn signal: 0–12 V blinking normally
- Left turn signal: constant ~0.5 V
- This confirms the issue is coming from the truck itself, not the trailer.
- Trailer turn/brake fuses (left and right) are not blown.
What’s strange: the right trailer turn signal still works even with the fuse removed. - Using JScan, I verified that all trailer outputs are enabled.
Even when disabling the trailer outputs in JScan, all trailer functions still work except the left turn signal.
At this point I’m a bit stuck.
Does anyone know how the trailer lighting is actually controlled on the RAM DT (BCM vs separate trailer module)?
Or has anyone experienced a similar issue with a dead left trailer turn signal output?
Any input would be greatly appreciated. Thanks!
