Marker Lights Not Working

[Ex-tenter]

As stated in title. Marker lights are not working. Left and right turn signals and brake lights work as expected, electric brakes work as expected. Checked pins on trailer and truck side with multimeter, everything seems okay on both sides. They were all working last fall, now not working, ALL marker lights.

Also reviewed this thread

Looking for more troubleshooting ideas.

[Ex-tenter]

Reviewed the thread again and re-checked the pins on the TT side. If I short the correct pins, all of the marker lights come on.

So, the lights are functional, but the TV for some reason is not providing the appropriate signal/voltage to make it happen. It's dark out now, I'll take another stab at it tomorrow, but any suggestions are welcome.

[grege]

Have you checked to see if any fuses on your truck blew?

[Ex-tenter]

Originally Posted by grege

Have you checked to see if any fuses on your truck blew?

Yes, I checked continuity on every fuse that had indications of being involved with the trailer. As my truck's brakes and lights all seem to be functioning, I'm assuming it's not the normal lights fuses.

[Mr. Dan]

Originally Posted by Ex-tenter

Yes, I checked continuity on every fuse that had indications of being involved with the trailer. As my truck's brakes and lights all seem to be functioning, I'm assuming it's not the normal lights fuses.

In a truck as new as yours, fuses for trailer functions are not the same as for the truck... may not even be in the same fuse panel.

[Ex-tenter]

Oh, sure. But I took the cover off the panel and it has a nice chart on the inside that shows all of the fuses and clearly labels which ones have what functions. There are a number of them specifically labeled for trailer functions. It's possible there's another fuse block hiding somewhere, but I have not been able to locate one, and I think it would be odd of Chevy to put some in this box, and some in another box. Not saying they didn't, just saying IMO it would be dumb. I'll have another look for another fuse block somewhere.

[clr]

It sounds like you have lost the ground connection for the marker lights. TT tend to use the metal of the unit as a ground return. So one wire to the marker lights is hot or 12vdc and the other connects to the metal of the TT. I would check the hot wire with a multimeter and insure that you have the 12vdc when the lights should be on. If you have power you will have to either correct the poor connection to the light or provide a new ground path for the light.

[mnoland30]

What do you mean "if I short the correct pins"? Use a multi-meter (or a test light) to check that you are getting power from the tow vehicle. Look online for information about which prongs supply ground and hot for marker lights. Check under the back of the truck to see if a wire pulled loose or has rubbed. Pull the fuse in your vehicle and check for continuity. Sometimes they blow and it isn't easy to see. Clean the connections with a wire brush. Let us know what you find.

[Larry-NC]

Originally Posted by Ex-tenter

Oh, sure. But I took the cover off the panel and it has a nice chart on the inside that shows all of the fuses and clearly labels which ones have what functions. There are a number of them specifically labeled for trailer functions. It's possible there's another fuse block hiding somewhere, but I have not been able to locate one, and I think it would be odd of Chevy to put some in this box, and some in another box. Not saying they didn't, just saying IMO it would be dumb. I'll have another look for another fuse block somewhere.

There are THREE fuse panels on a 2020 Silverado.

1. Under the hood
2. At the left end of the dashboard (open the driver's door and pull off the end of the dash)
3. At the right end of the dashboard (open the passenger's door and pull off the end of the dash)

If you RTFM (Read The Fine Manual), you will see the instructions and even be able to identify which panel has the trailer fuses. (I'm betting driver's side.)

[Larry-NC]

Originally Posted by clr

It sounds like you have lost the ground connection for the marker lights. TT tend to use the metal of the unit as a ground return. So one wire to the marker lights is hot or 12vdc and the other connects to the metal of the TT. I would check the hot wire with a multimeter and insure that you have the 12vdc when the lights should be on. If you have power you will have to either correct the poor connection to the light or provide a new ground path for the light.

Nope. The OP stated that when he jumpers +12 to the marker lights contact on the umbilical (11 o'clock to 1 o'clock) the lights come on. That establishes that the ground connection is okay.

[camaro80]

What I have experienced on my truck when hooked to my cattle trailer (same type of plug as RV), is that the blades in the plug eventually get squeezed together from repeated use so that they don't make good contact with the trailer. So I use a pick and screwdriver to spread both sides a little, and at the same time polish them up a little best I can. I've gotten things working again doing this occasionally.

[TGR]

Check the tow vehicle's wiring at the 7-pin connector with a multimeter or DC circuit tester. The running lights are on pin 3 and the ground is on pin 1.

To easily check the trailer's running lights, bridge pins 3 and 4 on the trailer's connector with a 10 or 15-amp fuse. The blades of the fuse will plug into your trailer's 7-pin connector with a little fussing. Your trailer's battery will now light the running lights. Of course, you need to ensure the trailer's battery is connected and supplying power to the trailer.

[Ex-tenter]

Originally Posted by camaro80

What I have experienced on my truck when hooked to my cattle trailer (same type of plug as RV), is that the blades in the plug eventually get squeezed together from repeated use so that they don't make good contact with the trailer. So I use a pick and screwdriver to spread both sides a little, and at the same time polish them up a little best I can. I've gotten things working again doing this occasionally.

I can see this being a thing, but my 2020 Chevy has only pulled this trailer less than 1000 miles, so I don't think it's the case for me. I'll look, but I'm not optimistic this is my answer.

[Ex-tenter]

Originally Posted by Larry-NC

Nope. The OP stated that when he jumpers +12 to the marker lights contact on the umbilical (11 o'clock to 1 o'clock) the lights come on. That establishes that the ground connection is okay.

To further confirm this, I purchased one of these:

https://smile.amazon.com/Camper-LITE...ps%2C89&sr=8-2

Connecting it to the trailer, the lights all come on. This pretty much mandates that the trouble is on the truck side.

[Ex-tenter]

Originally Posted by TGR

Check the tow vehicle's wiring at the 7-pin connector with a multimeter or DC circuit tester. The running lights are on pin 3 and the ground is on pin 1.

To easily check the trailer's running lights, bridge pins 3 and 4 on the trailer's connector with a 10 or 15-amp fuse. The blades of the fuse will plug into your trailer's 7-pin connector with a little fussing. Your trailer's battery will now light the running lights. Of course, you need to ensure the trailer's battery is connected and supplying power to the trailer.

I've done this; when connected in this way, the marker lights all come on. So the trailer side appears to be functioning correctly, the problem is almost certainly on the truck side.

[Ex-tenter]

Originally Posted by Larry-NC

There are THREE fuse panels on a 2020 Silverado.

1. Under the hood
2. At the left end of the dashboard (open the driver's door and pull off the end of the dash)
3. At the right end of the dashboard (open the passenger's door and pull off the end of the dash)

If you RTFM (Read The Fine Manual), you will see the instructions and even be able to identify which panel has the trailer fuses. (I'm betting driver's side.)

I've gone through the under-hood block entirely. I'll check the others after supper. Thanks for the pointer!

[Ex-tenter]

Originally Posted by Larry-NC

There are THREE fuse panels on a 2020 Silverado.

1. Under the hood
2. At the left end of the dashboard (open the driver's door and pull off the end of the dash)
3. At the right end of the dashboard (open the passenger's door and pull off the end of the dash)

If you RTFM (Read The Fine Manual), you will see the instructions and even be able to identify which panel has the trailer fuses. (I'm betting driver's side.)

So, you're correct about the fuse blocks on either end of the dash. Looking at both of those, only one spot is marked for anything to do with a trailer (Euro TRLR) and that location is not used. I am not hopeful these locations will be useful, but I will test all of the fuses with a multimeter. Most seemed to be indicated as relating to the interior comfort features - power seats, heating, etc.

[SailorSam20500]

I think on my Ford, I have to have the headlights or parking lights on to get the marker lights powered... I know one or the other need to be on to get my backup cam to work...

[clr]

You say the turn light work properly. Does that also mean that the tail lights work when the truck lights are on?

[Ex-tenter]

Originally Posted by clr

You say the turn light work properly. Does that also mean that the tail lights work when the truck lights are on?

No. I only get turn signals and brakes.