Troubleshooting Installation of Curt 4-Pole Wiring Harness C55378 in 2002 Toyota Tundra

Updated 07/12/2018 | Published 07/10/2018

Products Featured in This Question

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

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$66.73

Hook Probe Circuit Tester

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$13.43

Question:

I have hooked up a curt wiring harness part # 55378, in the rear drivers side grey plastic harness of toyota that you disconnect and then hook up the adapter is still not showing any power to the 4 pin flat. I have also hooked everything up to the battery correctly.

asked by: Steve B

Expert Reply:

The two wiring harness kits you referenced, Curt # C55378 and Tekonsha # 118378, are both correct fits for your 2002 Toyota Tundra. Both of these kits are multi-part harnesses that include the required fuse/fuse holder and the installation of the Curt kit in a 2002 Tundra is shown in the linked video.

The troubleshooting steps I suggest are to double-check that all connectors have no bent or damaged contacts, that they are fully seated together and that the ring terminal on the harness with the fuse holder is firmly attached to the battery + terminal and has the fuse installed. It is possible that the contacts in the vehicle connector in the engine compartment have oxidized or corroded enough to have a connection issue. You might try an aerosol electrical contact cleaner like Caig De-Oxit if you suspect oxidation of the contacts to be the problem.

Next you can test the BLACK wire leading into the left side of the converter box that mounts at the rear of the vehicle. This black wire brings in 12V operating power for the converter box. Please refer to the photo I included. You can use a circuit tester like # PTW2993 to check whether power is reaching the converter. If not, you may have an issue with the engine compartment harness that connects to the battery, or elsewhere in the vehicle wiring leading to the rear of the vehicle.

If you DO have 12V power entering the converter box, then next test the other wires to see if the vehicle lighting signals are also getting to the converter. Have a helper activate the brakes while you test the red wire; apply the right turn and test the green wire; and repeat this step for the left turn/yellow wire and taillights/brown wire.

If 12V power AND the various vehicle lighting input signals are all entering the box but there is still no output on the 4-pole, then the unit is likely to be defective or damaged. Without both power and input signals entering the converter there can be no output on the 4-pole.

Please let me know the outcome of these tests and if needed I will try to assist you further.