Troubleshooting Trailer Running Lights That Do Not Work on Wiring Harness in 2008 Honda Element  

Question:

Expert Reply:

Thank you for your hitch purchase earlier this year.

When some trailer lights work, such as the brake and turn lights, but the running lights do not work properly, the most common cause is a weak ground connection. This is because a weak ground will be able to pass enough current to operate lights that come on sometimes, such as turn and brake lights, but NOT enough current to also operate the always-on running lights. If a certain function does not work at all at any time then it is likely to be a blown fuse or a short in that circuit's wiring.

Your first step is to check that your trailer wiring harness' white ground wire, such as the one on part # C56029, is firmly attached to a clean bare metal surface on the Element. All you may need to do is tighten the self tapping screw that holds the ring terminal in place. If that does not do it, then remove the ground wire and clean and/or sand that spot to remove any paint, primer, dirt, grease or corrosion.

One you have a nice clean grounding point you can re-attach the ground terminal and if you like add a dab of protective dielectric grease like # LT37534 that will prevent entry of water and dirt into the connection.

If that does not let the running lights work properly then you'll need a tester like # PTW2993 to test the wires going INTO the wiring harness to be sure the car's running light signal is reaching the converter. The linked video shows the use of a tester to detect a signal. If you test the brown running light wire that goes into the converter and it DOES have a signal when the headlights are on but there is no signal on the 4-pole's pin for the brown wire, THEN the converter is bad.

You can also check the contacts on the connector to see if perhaps one of the pins is bent, dirty or corroded. Also check that both the vehicle and trailer connectors are free of any trapped dirt or corrosion, which can appear as a slight whitish or greenish discoloration on the pins. Clean as needed.

An article with wiring troubleshooting tips is also linked for you reference.

expert reply by: Adam R

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