Trailer Tail Light Adapter Installation on a 2004 Toyota
Tacoma Pickup Using a Hopkins 46155 5-wire to 4-wire Converter


The 2004 Toyota Tacoma Regular Cab does not come with a connector for trailer lights as standard equipment. Also, trailer lights typically use the same bulb filament for brake and turn signals, whereas the Tacoma has separate lights for these functions. Thus, the trailer lights cannot be directly connected to the pickup tail light wires. To add a 4-wire trailer tail light jack to vehicles like this, an adapter such as the Hopkins 46155 must be used. The adapter converts the 5-wire system on the vehicle to the 4-wire system on the trailer.

In addition to the adapter, the Hopkins 46155 Kit includes splices to attach the adapter wires to the vehicle wires and a four foot long 4-wire extension cord to connect the adapter to the trailer light plug. It also includes a circuit tester, which is an LED that lights when the alligator clip is connected to ground, and a positive voltage is applied to the sharp tip.

The first installation step is to locate the wires going to the vehicle tail lights. In the case of the Tacoma, all the needed wires are accessible in the main tail light wiring harness above the left frame member (see the first photograph below). The protective plastic wire shield is split lengthwise, so the wires can be easily exposed at any point.

The next step is to identify the vehicle wires that correspond to the various light functions. The wires can be identified by piercing the wire insulation with the tester tip while each light is turned on. In this particular case, it was easier to remove and unplug the tail light assemblies, and apply the tester to the exposed jacks. Note that Table 1 below applies only to the specific vehicle described here; other makes and models will very likely have different color assignments.

After the vehicle wires are identified, the adapter can be positioned, and the 5-wire side connected with the splices provided. The green right turn wire on the adapter is longer than the other wires, but the extra length was not needed in this installation, so it was trimmed to the same length as the other wires. The white ground wire was also longer than needed, so the lug was removed and the wire trimmed. The lug was then reattached, and the wire/lug junction was soldered to ensure that the connection was good.

The first photo below shows the installation before the protective shielding was added. Note that the ground point on the frame was sanded down to bare metal before the screw was put in, again to ensure a good connection.

The second and third photos show the wires and adapter after the protective shielding was installed. The assembly was attached to the existing wires and the pickup body for support, and the 4-wire extension was routed through the hole above the license plate. Finally, the area on the frame that was sanded down to bare metal was sprayed with rust-resistant paint.

Table 2 below shows the OFF/ON relationship between the vehicle brake light, a vehicle turn signal light, and the trailer shared light. Notice that the vehicle turn signal light and the trailer light blink in unison if the brakes are not applied, but they blink alternately if the brakes are applied.


Table 1 - Wire Functions and Colors for 5-Wire Side
Function Pickup Wires Adapter Wires
Ground White/Blk Stripe (Note 1) White (Note 1)
Tail Green Brown
Left Turn Green/Blk Stripe Yellow
Brake Green/White Stripe Red
Right Turn Green/Yellow Stripe Green
Back Up Red/Blk Stripe (Note 2)  



1. The white adapter ground wire is not connected to the vehicle lights ground wire; rather it is connected to the frame with a
self-tapping screw.

2. The Back Up light wire is not connected to the adapter.





Table 2 - Shared Light Truth Table
Vehicle Brake Light Vehicle Turn Signal Light Trailer Shared Light