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Dodge Ram 2002-2008: Why Aren't My Trailer Lights Working?

Malfunctioning lights on your boat trailer, hauler, or camper might indicate grounding problems or something more complex. Read on for a fix to your particular issue.

By Richard Bowen - July 17, 2015

This article applies to the Dodge Ram (2002-2008).

Have the lights on your Ram's trailer been malfunctioning? From blown fuses, relays and bulbs, to broken or crimping wires, to poorly-wired connectors, there are many things that could turn out to be the actual culprit. Luckily, troubleshooting the possible issue is inexpensive, and no specialized skills are required. Keep reading to learn what might be wrong with your trailer lights.

Materials Needed

  • Solder
  • Soldering gun
  • Wire
  • Trailer tester (optional)
  • Multi-meter
  • Modulite unit (optional)

Step 1 – Test the trailer

Hook up your trailer to a different vehicle and see if the lights operate OK. If they don't, then the issue is with the trailer, not the truck.

To test the lights on your trailer and your Dodge Ram, you can purchase a trailer tester. Click here to check out trailer testers.

Figure 1. Testing the trailer lights.

If your trailer lights are still not working, proceed to Step 2.

Step 2 – Check the fuses, relays and bulbs

Check any fuses and relays that pertain to the Ram's trailer light hookup (turn signals, brake lights, running lights). Also check for burned out light bulbs.

Figure 2. Fuses and relays.

If all fuses and relays look okay and are dry from moisture, continue on to Step 3.

Step 3 – Check the trailer grounding

Make sure the main ground is solid and secure. Most trailers ground to the hitch from the truck. Try grounding instead to the tongue area or to the frame for a better ground. Also check each light's ground on the trailer.

Figure 3. Make sure the grounding current can safely run through to the light.

Pro Tip

Run a ground wire from each light to the frame. Use star washers for a good connection.

If the grounding checks out and the lights are still not working, move on to Step 4.

Step 4 – Update the Totally Integrated Power Module (TIPM)

This part regulates and controls numerous electrical functions on your Dodge Ram, including trailer lights. There's no need to install a new TIPM; it may just need a program update. Take your truck to an authorized Dodge dealer and have them reprogram the unit.

Figure 4. TIPM unit.

Pro Tip

If the trailer has a ground short, reprogramming the TIPM may help in the short term, but the problem may may recur later on.

If the unit has been updated and the lights are not working, then soldier on to Step 5.

Step 5 – Rewire the lights

If reprogramming the TIPM does not help, bypass the TIPM completely by rewiring the trailer lights.

Figure 5. Choose a connector that has the right number of pins for the functions of your trailer.

If updating and rewiring the TIPM hasn't solved it, then go to Step 6.

Step 6 – Check for pinching or breaks in wires

Look for broken or pinched wires. Or, there could be a break in the wire that you cannot see. To remedy an invisible break, solder a jumper wire from the truck wire to the trailer wire.

Figure 6. Here is an example of wiring pinched from the the module and racking.

Go to Step 7 for continued troubleshooting.

Step 7 – Check for proper crimping

If you are crimping wires to make the trailer light connection, be sure you crimp the wires firmly.

Figure 7. If the crimp is bad, then the current will not be able to pass.

If the wires look good and have no pinches/exposed wire then persist to Step 8.

Step 8 – Check the truck connector

One Dodge Ram owner reports the seven-pin connector on his vehicle was not wired correctly from the factory. Use a multi-meter to check each of the leads.

Figure 8. Check the leads to see if the problem is stemming from the light connections.

Recommence to Step 9 for the end-all-be-all fix.

Step 9 – Install Modulite 119190 unit

If all else fails and your trailer lights are still not working, you may want to consider installing a Modulite 119190 unit. One owner on the forums installed this unit with good results. Pick up the input feeds from the Dodge Ram tail lights in the wiring harness then splice the output signals into the trailer's tow connector. Click here to check out information about Modulite 119190 units.

Figure 9. The Modulite 119190 features circuit protection and is powered by the truck battery.

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