Troubleshooting Curt # C55341 Wiring Harness Installation in 1997 Toyota 4Runner

Updated 03/19/2015 | Published 03/18/2015

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(49)

$45.73

Hook Probe Circuit Tester

(60)

$13.72

Question:

I just received the Curt 55341 custome wiring harness for my 97 Toyota 4Runner. I hooked it up per the instructions and when I took a test meter to the trailer plug, a strange thing happens. With the headlights off, the brake and turn signals work fine either independently or together, but as soon as I turn on the headlights, the brake and turn signal do not function, only the tail lights function. So I disconnected the module from power, made sure the ground was solid and tried again. Same result. The tow vehicle lights all function correctly. The module wiring all looks good. Could the module be bad?

asked by: Alvin B

Expert Reply:

Thank you for your recent purchase of a Curt wiring harness # C55341 from etrailer.

The ground wire connection, which you note you have already re-checked, would indeed be my first suspicion based on the harness' behavior you describe. It can often happen that a weak ground will let just enough current to pass to allow some lights to work but not others. Turn signals, since they do not remain on at all times, draw less current and may often be the function that works while a function like the running lights, which are on continuously, do not have enough current to operate. You can still try running a ground jumper wire from the harness ground wire direct to the battery negative terminal as a test to see if the ground is the issue.

Make sure you have the power wire connected to the battery and not to another 12V power outlet in the vehicle.

Once the ground has been eliminated as a cause I suggest you apply the tester to the wiring on the harness to confirm if it is defective or damaged.

Apply a tester like # PTW2993 to the wiring on the input (left) side of the module while a helper activates each function on the vehicle. You will test one wire at a time while that function is activated. Test the yellow wire leading into the left side of the box while the left turn signal is activated; if your tester detects the appropriate on-and-off blinking signal then test the yellow wire on the output (right) side of the box.

Repeat this test on the two green wires for the right turn signal, and on the brown wires for the running lights. Running lights should be an always-on signal on both input and output sides. If the correct signal is going in but NOT coming out, then the harness is bad.

It is possible that if you have plugged your trailer in, and there is a problem within the trailer's wiring, that could have shorted out the harness. Check your trailer wiring from the connector to the lights looking for any signs of cracked or worn insulation that could have caused a short. Pay particular attention to spots where the wire has to make sharp bends or where it comes into contact with the trailer frame.

The linked article offers additional troubleshooting help.