Turn lights and brake lights not working

[tylerjaywilson]

Hi Everyone,

I recently purchased a 2005 Fleetwood Sante Fe tent trailer. I am pulling it with a 2016 Honda Pilot EX. The connection from the trailer to the Pilot is a 7 pin connector. I can get all the running lights to work but the turn lights and brake lights aren't working. This is what I've checked up to this point.

1. There are 3 fuse locations for the trailer on the Pilot. They are #2 location: TRL MAIN, #3 location: TRL E-BRAKE, #11 location: TRL CHARGE. I've checked all of these fuses and they are good.
2. I heard that there is potential interference when the TRL CHARGE fuse is placed. I removed that and had the same issue with the brake and turn lights, so I have replaced that fuse.
3. I replaced all the lights with LEDs to see if I had a bad bulb somewhere. The new LEDs didn't change anything.
4. I hooked up my father's truck to my trailer and it WORKED!
5. I have probed the 7-pin connector with my multimeter. I can see that I have 12V and the running lights do work. I seem to be seeing some fluctuation on the pins that run to the turn signals but it is only reaching a few hundred millivolts instead of the 12V swing that is expected.

It seems to be an issue with my Pilot. Outside of the fuses being good and functional, I'm not sure where else to look. Any advice?

 

[Mark_K5LXP]

Check for 12V & flasher signal on the fuses.

Mark B.
Albuquerque, NM

 

[tylerjaywilson]

Thanks Mark. Are you saying to probe the signals at the fuse with a multimeter? I have checked and verified continuity from one side of the fuse to the other.

 

[Mark_K5LXP]

Measuring at the fuse will show if power is at least at that point. If it's there, then the trouble is somewhere between the fuseblock and the bumper. If it's not, it's upstream, maybe the DC distribution box under the hood.

Assuming they're ATC fuses. Probe the little metal buttons there on the face of it with the positive probe, negative probe on chassis ground. If the fuse, and the signal is good you should see voltage on both sides of it.

If it checks out OK there, then you can test it again at the bumper to see if maybe the pin assignments aren't what you're expecting.

Mark B.
Albuquerque, NM

 

[tylerjaywilson]

Mark,

Thanks again. I did check both sides of the 3 fuses. All 3 look good. The voltage readings I'm getting at the tail light are the same as before. 3 of the pins are good though. I have the running lights working, the ground pin, and the 12V pin that charges the battery. Maybe some internal controller after the fuses that isn't working correctly?

 

[Mark_K5LXP]

This isn't about checking the fuses - it's to see if the correct signals are present at those fuses. So, brake and turn signals/voltages should be present there.

Mark B.
Albuquerque, NM

 

[tylerjaywilson]

I'm seeing 12V, as expected, on the fuses. However, when I have my hazard lights flashing, I don't see any voltage toggling on the fuses. I see a constant 12V. I would imagine the Pilot has a controller somewhere to take the 12V signal and oscillate it high and then low to blink the turn signals. Maybe I'm wrong about this?

 

[Mark_K5LXP]

Likely guess, the flasher might be downstream of the fuse. One thing about hazard lights is it depends on whether you have combined brake/signals or separate for which bulb gets flashed. I would consider hazard a separate test when it comes to brake/turn on a trailer because (at least in the olden days) it had a separate flasher and circuit path (battery hot). Sometimes there's a "module" that isolates brake and turn signals for trailers (at least in aftermarket kits) and there's a chance that might be popped. Not sure that's part of an OEM connection or not though.

Mark B.
Albuquerque, NM

 

[Gary RV_Wizard]

I would imagine the Pilot has a controller somewhere to take the 12V signal and oscillate it high and then low to blink the turn signals. Maybe I'm wrong about this?

That's correct. Usually called a "flasher", for the turn signals or emergency flashers. The brake lights, though, is a simple switch activated by the brake pedal.

Stop & turn signals to the trailer are provided by the same pair of pins in the 7-pin Bargman connector (see attachment). With the turn signals off, you should see a simple voltage change at those two pins when the brake pedal is pressed. Should be 12-14v with brakes on and 0 when off. Ditto with the brakes off and the turn signal or emergency flashers on. The blink may be too fast for the voltage to stabilize at a full 12+ volts, but you should see a definite strong voltage with each "blink".

You didn't mention if the trailer connector is factory wiring or aftermarket. Your Pilot almost sure has digital multiplexed stop/turn wiring so the trailer plug has to be wired to a real (analog) 12v source, usually provided by a trailer light controller. A factory trailer plug would almost sure have this, but an aftermarket installer may not have realized it would be required. You may also need a conversion adapter if the Pilot has separate stop & turn signals. Those need to be combined for the trailer bulbs. Again, a factory wired 7-pin should already have that.

 

[tylerjaywilson]

Thanks for the feedback. I found a random YouTube video that solved my issue. There is a undocumented fuse box in the interior, rear, driver's side portion of the car. When I located those fuses (4 in total), there was one fuse that was blown. Upon replacement, it fixed the issue. Thanks for the help!