TRAILER LIGHTS MALIFUNCTIONING

Question:

On my 2007 Silverado Classic, once I hook up my food trailer only the right side lights on the trailer work. The left side doesn't work so I can't travel at night. All the lights on the truck work properly.

asked by: ROOSEVELT H

Expert Reply:

The first step to every trailer wiring troubleshoot is to determine if the problem is with the trailer wiring or the vehicle's wiring. The easiest way to to this is to try the trailer with another vehicle. If the lights work fine, you've verified that the problem is with the truck. If not, the problem is on the trailer. You can also try another trailer on your vehicle to determine where the problem lies. If this isn't possible or convenient, you can use a circuit tester like # PTW2993. Have a helper activate each taillight function as you use the tester to test each pin on the trailer connector as each lighting function is activated. If each pin lights up the tester when its function is activated, then the problem is with the trailer wiring. Start at the connector, and examine it for damage or green and white corrosion in the sockets. If you see corrosion, it's possible that the corrosion has spread to the interior and is preventing the signal from getting through. Replace if necessary. Continue following the trailer connector back to each lamp, looking for loose or broken connections. Repair as needed.

If the trailer connector on the vehicle didn't test out as it should, then there are a couple of possibilities. The two most likely are a blown fuse or a corroded or damaged trailer connector on the truck. On a 2007 Silverado Classic (mechanically and visually identical to a 2006 Silverado as opposed to the 2007 New Body Style model) check the fuse panel on the side of the dashboard that sits up against the driver's side door. Check the 'LT TRLR ST/TRN' fuse and replace if necessary. If the fuse is blown, after the fuse is replaced you'll want to check the trailer wiring to find the short that made the fuse blow, otherwise you'll continue blowing fuses.

To troubleshoot the trailer connector on the back bumper, disconnect the trailer connector from the tow package harness where it plugs into the rear of the connector. Use the circuit tester to check the contacts on the tow package harness as each function is activated, specifically the left turn/brake. If you get signal on the tow package harness but not the trailer connector, the connector is bad and needs to be replaced with # PK11916. I'll link you to our trailer wiring troubleshooting article which you might find helpful.

expert reply by: Mike L