Stumped by trailer wiring

Pop-up camper wiring (7 pin) works perfectly on my son-in-law's Dodge Ram. Nothing lights up on my other son-in-law's 2008 Tacoma OR my nephew's Tacoma. I did notice that the Ram and trailer needed to be hooked up to complete proper ground. Could this be a clue to Tacoma issue and how do I fix?

 

Check the fuses for the tow package in the fuse block under the hood. Also look at the tacoma's plugs if they are corroded badly then could not be getting a good connection. Make sure the plug is all the way in seems simple but seen that before.

 

If ram had to be actually hooked to the ball to get lights on then the 7 pin probably has a bad ground pin as noted above so clean the 7 pin plug connectors (fine sand paper or 3M pad cut to fit in on a screwdriver blade or such). Use a multimeter to verify a good ground and check the other connectors for hot - need the correct pinout.

 

you need to be hooked to the ball, grounds the connection, then you should be fine

 

^ Bad advice. You should NEVER rely on the ball for a ground connection.

 

This ^^^^^^^^^^

That is what the wire is for in the harness. If the trailer is wired this way it is wrong.

 

yes that's correct the circuit between the truck and trailer needs to be grounded. The battery is grounded to the truck, so to complete the circuit, the trailer needs to either be hitched to the truck or grounded through the plug to the truck. I agree that that's not the correct way to solve the problem but if it does for some oh well.

 

As others have said, check the ground wire on the trailer side. Most likely it is corrosion at the plug, but could also be the ground wire connection at the trailer frame.

 

Where is the WHITE wire connected to on the camper side of the harness?
Also, do you you have access to a test light?