Low Voltage on Factory 4-Way Trailer Connector on a 2002 Toyota Tundra

Updated 07/24/2018 | Published 07/22/2018

Question:

I am only getting 4 to 5 volts out of the factory installed 4 pin harness. What would cause the lower voltage. Should I check the pin with the black wire for 12 volts on the harness at the back of the truck?

asked by: Joe

Expert Reply:

If the factory tow package wiring on your 2002 Toyota Tundra uses both fuses and relays then the issue could be a faulty relay. They can sometimes still allow some power to trickle back even if they are bad so that is one thing to check. There could also be a corrosion issue, ground problem, or wiring problem.

If you are testing the pins on the 4-Way go ahead and test one of the wires going to the connector instead. If you get the proper voltage on the wire but not the pin then it is likely corrosion or crud limiting the voltage. Cleaning out the connector or replacing it with # HM48190 would fix the problem.

A weak ground could also cause this issue. You could attach a jumper wire to the trailer connector ground wire and attach it to a bare metal surface for a better ground.

You can also inspect the wiring as best as you are able and fix any damaged or pinched wires.

expert reply by: Michael H