My 2003 Silverado has a problem with the trailer lights. The stop lights and the hazard warning lights work fine, but the running lights and turn signals do not work. There is no current at the trailer electrical connector. I looked in my owners manual and found the "Center Instrument Panel Fuse Block" that contains a "Trailer 6-Way". But, I can see the center instrument panel utility block but I can't seem to figure out how to access the Trailer 6-Way to check it out. Can I get some quidance on how to solve this trailer light problem? Thanks in advance for your help.
check the brown wire on the tailight harness on the truck chances are it shorted and broke away from the assembly. the fuse is in the junction box under the hood.
check the wiring from the tailights back to the fuse panel, it sounds like an open connection. if i recall correctly check under the dash on the drivers side near the fuse panel for a bunch of wires in a bundle and look carefully for a wire or two that are cut/shorted/or seperated, you can also check under the drivers side kick panel by the hood release.
make sure the ground wire is hooked up, i've seen many trailers where the ground wire just hangs, then your relying on the ground to work between the ball and the hitch, not typically a good ground.
you probbally popped a fuse. Check all fuses in the car and trailer. Make sure all the lights are in good condition and that the connections going to the trailer from the car are in good shape.
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Brake light switch? The cruise and brake lights problems are likely related. The cruise control cuts out when you press on the brakes. I had a van where the cruse wouldn't engage. Then someone pointed out my brake lights were always on. It was the switch.
Which fuse did you replace ? The one in the under hood fuse box or one of the two in the I/P fuse box . Do the CHMSL - center high mount stop lamps work correctly ? Here is a description how they work . Stop Lamps
The STOP LP 25 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the STOP 15 A fuse and the CHMSL 10 A fuse in the I/P fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits. The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.
Does yours have trailer light hook up ? If so check trailer wiring connector for corrosion . Also check the turn signal / hazard module .
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Stop Lamps
The STOP LP 25-amp fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the STOP 15-amp fuse and the center high mounted stop lamp (CHMSL) 10-amp fuse in the instrument panel (I/P) fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits. The voltage from the CHMSL 10-amp fuse is to the CHMSL and the trailer jumper harness. The voltage from the STOP 15-amp fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.
I think The turn signal/hazard module has something to do with the lights flashing .From looking at a wiring diagram B+ voltage from the STOP LP fuse 25amp in the under hood fuse box supply's the brake light switch , from there it feeds B+ to VEH STOP fuse 15amp and VEH CHMSL fuse 10amp an to stop lamp switch signal to the turn signal flasher module which is suppose to control the trailer stop lights . Do you have a connection for a trailer hook up ?
Remove both LT an RT TRLR fuse's both 10 amp from the I/P fuse block an see if the problem goes away .
Do you tow a trailer ? Check the trailer connector for corrosion !
Lighting control module ? ?????? Hazard / flasher module ! Now ( there''s not even an electrical signal where the fuse plugs into the interior fuse panel.) What FUSE ??????
Stop Lamps
The STOP LP 25 A fuse in the underhood fuse block supplies battery positive voltage to the normally open stop lamp switch. When the driver presses the brake pedal, the switch contacts close and battery positive voltage is supplied to both the STOP 15 A fuse and the CHMSL 10 A fuse in the I/P fuse block, and to the turn signal/hazard module. The turn signal/hazard module then supplies voltage to both of the trailer rear turn/stop lamp supply voltage circuits. The voltage from the CHMSL 10 A fuse is to the center high mounted stop lamp (CHMSL) and the trailer jumper harness. The voltage from the STOP 15 A fuse is to the stop lamps, throttle actuator control (TAC) module, and the cruise control.
Backup Lamps
The backup lamp request signal is sent from the powertrain control module (PCM) to the body control module (BCM) on the Class 2 message system. This signal is based on the park neutral position (PNP) switch signal. The BCM supplies voltage on the backup lamp supply voltage circuit to the backup lamps and to the automatic day/night mirror. Voltage for the courtesy lamp supply voltage circuit and backup lamp supply voltage circuit is from the TBC B fuse in the instrument panel fuse block directly through the BCM to these circuits. A short to ground on either of these circuits will open the fuse. The backup lamps are grounded at G401.
For trailer wiring, a separate backup lamp circuit is connected through the underhood fuse block from the TRLR B/U 10 A fuse to the trailer wiring harness.
Turn Signal/Hazard Lamps
The IGN E 10 A fuse in the underhood fuse block supplies battery positive voltage to the turn signal/hazard switch assembly. The FLASH 25 A fuse in the I/P fuse block supplies battery positive voltage to the turn signal/flasher module and ground is supplied at G200. When the turn signal switch is placed in either the left or right position, a voltage signal is completed from the turn signal switch to the turn sign/flasher module. When the hazard flasher switch is activated, a ground signal is completed from the turn signal/hazard switch to the turn sign/flasher module. The turn sign/flasher module then sends an on-off voltage signal through the LT TRLR, RT TRLR, LT TURN or RT TURN 10 A fuses in the I/P fuse block to the appropriate turn signal or to all 4 fuses for hazard operation. The instrument panel cluster (IPC) indicators receive voltage from the LT TURN and RT TURN fuses as well as the DDM/PDM for the mirror turn signals. The DDM/PDM has no function or control of the mirror turn signals other that a pass through connection for the circuits. The audio chime is also activated when the turn signals are on. When the hazard switch is pressed, all turn signal lamps will flash including both IPC turn indicators. The front turn signals are grounded at G100. The rear turn signals are grounded at G401. The Mirror turn signals are grounded by the DDM/PDM.
Do you know how to do automotive electrical circuit testing with a test light or volt meter ? How to read an use a wiring diagram to pin point testing points . ( connectors , fuse locations etc... ) How to use a power flow chart ? Here is a site for just such info .
I have the exact same issue. I have also tested my trailer on other vehicles and it works fine. I even purchased a light up tester and found the problem at the harness. It seems like a bad ground to me but I can't seem to find one.
The trailer lights have a common brake/turn wire while the truck has seperate turn and brake lights. I think the problem lies with the device that marries the two for the trailer wiring but I don't know where to find it?
Check at the light socket in the rear, where your lights don't work. You need a test light or a voltage meter, and check to see that you have a groun there, power for your parking light, and power to the brake light. You should have power for the parking lights seeing that it works, and a ground. Just verify that your power for the brakes is getting to the bulb, or not. Just a good place to start.
And you are correct that if the third brake light works (top) your brake light switch is fine.
Look under the dashboard, next to/above the park brake pedal, for the interior fuse box. It has a black plastic cover. Remove the TAIL fuse, and see if it is blown. This should get you fixed up. Hope this helps, and Thanks for choosing FixYa.
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