My brake lights not working?

Does your truck have a pushrod that actuates the b rake switch at the pedal?

Check it to make sure the retaining clip is not loose or missing. Also check to see if the electrical connectrions have not come loose and that the switch is getting actuated with th epedal being pressed.

Let me know if that helps.

Here is a schematic of the exterior lights.

Check the Orange wire at brake switch, on top of brake pedal for battery voltage. If voltage is available, use a jumper wire to bridge the Orange and White wire. If brake lights come on, the switch is bad or out of adjustment.

Do you mean only the trailer stop lights are not working?
Are the brake lights on vehicle body working correctly?

The CHMSL fuse (10A) is for the brake lights. If battery voltage is not available athe trailer connector, check the CHMSL fuse. Use a test lamp to test both ends of the fuse. If voltage is available and none found at trailer connector (Light Blue wire), you have an open circuit between the fuse and trailer connector.

You're welcome.

Sorry it took me so long as I misunderstood your question.

Have a nice day.

The lite blue wire is voltage for brake lamps. Black wire is ground.

Did you checked the CHMSL fuse 10amp it powers the 3rd light-if okay-inspect and test the light blue wire at the body junction box left side of dash

Hi and thanks for using 2CarPros. Com.

It sounds like you have a bad brake light switch. Have you checked it? It is located at the top of the brake pedal. Here are the directions for removal and replacement if you find it is bad. The attached picture shows the switch and correlates with these directions.

CAUTION: Refer to Battery Disconnect Caution in Service Precautions.

1. Disconnect the negative battery cable.
2. Disable the SIR.
3. Remove the pushrod retainer from the brake pedal pin. Use snap ring pliers.
4. Unsnap the stoplamp switch from the pushrod.
5. Disconnect the electrical connector from the stoplamp switch.

INSTALLATION PROCEDURE

1. Connect the electrical connector to the stoplamp switch.
2. Snap the stoplamp switch onto the pushrod.
3. Install a new pushrod retainer on the brake pedal pin. Use an 11 mm (7/16 inch) socket in order to push a new clip onto the pin.
4. Connect the negative battery cable.
5. Enable the SIR.

Let me know if this helps.

Take care,
Joe

Check the fuses in the diagram, check the actual voltage readings. This is for brake lites. The stop lamp fuse and center high-mount fuse, underhood fuse block. With the brake switch activated, the voltage should be close to battery voltage. Yes, it does sound like it could be a grounD problem?

this guide will help

https://www.2carpros.com/articles/brake-lights-not-working

It might be the multi-function switch (turn signal switch) has an open circuit. need to check the bulbs, fuses and relay first. I'm attaching links and diagrams below to help you locate them. If your high mount brake lamp is working because it is on a different circuit than then the rear stop lamps and you can eliminate the brake lamp switch. Let us know if this information was helpful and if you need any more help.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

this guide can help as well

https://www.2carpros.com/articles/brake-lights-not-working

https://www.2carpros.com/articles/turn-signal-switch-replacement

Check out the diagrams (Below). Please let us know what happens.

Does the highmount brake lite work? Did you check for voltage going to the brake switch, orange. The lower brake lites are wired through the multifunction switch. At the lower rear, the brake lites and turn signals use the same bulb filament, just not at the same time. Check voltage and ground at the rear.

In the diagram, the brown wire is voltage for tail lamps, the other color wires are for stop/turn. The black wire is ground.