Good Afternoon.

I have been reading this forum for the last two hours to see if anyone had a similar problem and I could not locate one. Seems that there is a lot of good experience here and maybe you can help.

I have a 2001 Chevy Silverado with the 8.1L engine and Allison transmission. It is a crew cab and a long bed - I am the original owner and the truck has about 45,000 miles on it; It is not a daily driver. In reading around I see that a lot of the responders like to have an understanding about the truck and its use - I hope that works.

So here is the issue. I have a fifth wheel trailer that I tow and the other day at a stop light the driver next to me said that I did not have any trailer brake lights. I pulled over and being the only person in the truck, I checked the blinkers - first the right then the left and they worked fine on both the truck and the trailer. I thought the guy was messing with me because I could see the reflection of the truck brake light from the truck on the trailer when I hit the brakes. Went on home and got my wife to get in the car and check the lights again - both blinkers work, however the trailer brake lights do not work (the truck brake lights do work). The trailer lights do not have a separate amber and red light for turn and brake so if one is working shouldn't the other...?

Here is what I have done to solve the problem. I replaced the seven pin cable on the trailer. ( I thought that might have been the problem becayse it is always getting tossed around) I have removed the Prodigy connections and cleaned them. I have removed the trailer plug wire connection and cleaned it. I checked each brake light for dirt and grime, cleaning where necessary. I checked the fuses under the hood (there was not a trailer brake fuse, just a LT and RT fuse) those too looked fine. I have tail lights when I turn the lights on. I have two connections for my fifth wheel, one in the bed and the other at the bumper - neither work and both have the same output. Lastly, I checked the ground (the one for the fifth wheel connection in the bed) and it looks good.

I then asked my neighbor if I could borrow his truck and hook it to my trailer. We hooked up his truck to my trailer and everything worked fine. This leads me to believe that the issue is with the truck and not the trailer.

Any suggestions on why the truck brake light is working fine and the trailer brake light is not working? Does the hazard circuit have anything to do with the brake light? My third brake light on the truck is working correctly.

It has worked in the past. Is there a fuse that I am missing or...?

Thanks in advance.
Lake

Did you check the back of the truck plug to be sure the wire hasn't corroded/broken off?

Phat Rat - thanks for the suggestion, I just disconnected the harness from the connector, blew it out and reconnected it, it did not solve the problem.

I wish I could wager on this one.

You will need to replace the flasher (turn signal) module.

Follow my logic.....
The turn and stop for either trailer taillamp share the same wire and fuse (on the truck), and turn is working. Stop lamps on the truck are working, but not on the trailer, however, there is only one set of stoplamp contacts used for brake lamp activation (so stoplamp switch failure would mean no brake lights, anywhere).....

If you carefully examine your truck taillights, in action, you'll notice that the turn and brake filaments are actually two seperate bulbs, and your trailer has turn and brake combined in the same filament. How'd they do that??? The flasher module contains the logic circuit that let's brake and turn down the same wire without letting brake voltage back into the turn circuit (Your front turn signals would glow bright upon every brake application if the were no logic circuit in the module).

heymccall, how much do you want to bet?:D My money is on the 4-way flasher switch. Very common problem on the 01-02's. Take a penny (or anything else that size) and jam it on the right side of the 4-way flasher switch. For some reason that will temporarily fix the problem until you can get a new switch.

Thanks Guys - In looking up the turn signal assembly, it appears to be a stealership remove and replace item since the steering wheel has to come off. That assembly is about $300 bucks - is controls the wipers, cruise control, blinkers and hazard lights.

As dumb as this sounds, I can't locate a four-way flasher switch. (unless you are referring to the hazard light switch) Any pointers on where it is and which side is the right side for the penny trick?

Thanks again,
Lake

Yes, I'm talking about the hazard light switch on the top of the steering column. I know it sounds crazy, but the TRAILER brake light power travels through that button. Stick the penny on the right side of the switch. All 5 or 6 that I have "fixed" took the penny on that side.

Thanks Guys - In looking up the turn signal assembly, it appears to be a stealership remove and replace item since the steering wheel has to come off. That assembly is about $300 bucks - is controls the wipers, cruise control, blinkers and hazard lights.

As dumb as this sounds, I can't locate a four-way flasher switch. (unless you are referring to the hazard light switch) Any pointers on where it is and which side is the right side for the penny trick?

Thanks again,
Lake

I paid $150 to at the stealer to buy each of several multi-function switches on '06s (not broken, but to add cruise control)... It's been a little while, but I seem to recall that to change the switch, that after removing the airbag, you can access the screw(s) that would normally require wheel removal. I know for certain that an '06 multifunction switch can be done without entire steering wheel removal, I'm just not as sure on an '01.

Also, if the 4way switch is suspected to be bad, I've found that repeated cycling will temporarily "clean" the contacts inside the 4way switch.

I know it sounds crazy, but the TRAILER brake light power travels through that button. Stick the penny on the right side of the switch. All 5 or 6 that I have "fixed" took the penny on that side.


Man did that do the trick, I have $0.13 invested in this repair. Three penny's and a dime to fill the gap on that side and it works like a charm.

Thanks

Yes, I'm talking about the hazard light switch on the top of the steering column. I know it sounds crazy, but the TRAILER brake light power travels through that button. Stick the penny on the right side of the switch. All 5 or 6 that I have "fixed" took the penny on that side.


nice tip sounds like you nailed it,I'll keep that one in the memory bank. Does that apply to the newer years as well?

nice tip sounds like you nailed it,I'll keep that one in the memory bank. Does that apply to the newer years as well?

2003 and newer got a different button and I haven't seen the problem.

I did the penny trick this afternoon too! After giving up on self diagnosis I found your site. The penny worked like a charm, Thanks

WOW, I have been beating my head against my truck for HOURS, not to mentioned stumped every buddy of mine i thought would have a good idea. TTT for people to read this, good little trick to know.

Just had the same problem with my 2003 GMC 2500 Hd Duramax and 2010 Big Horn 3055 fifth wheel trailer left side brake lights. As a result of the information that was posted I was able to get the GMC dealer to check out the hazard module, find it faulty and replace it under my extended warranty. The lights all work ok now. One thing that complicated my problem was that the lights would all work ok when first hooked up but after a few brake cycles the light would no longer function, and I did not know it until somone told me my left brake lights were not working.Thanks for the post and help.