Sometimes when towing my trailer with my 2001 blazer stepping on my brake pedal causes the dash lights to shut off? This only happens with the trailer hooked up and not every time. Any ideas?

you should have a brown,yellow, green and white for lights and a red and black for the brake electrical which is controlled from the front of the towing vehicle..only the front trailer axle has brakes in it..not all 4 wheels..if yopu connect a spare battery to the trailer brakes they should lock the wheels(or a strong battery charger..)the vehicle should have a auxilary brake control box under the dash within reach of the driver.. this has most of the controls in it..it should alsdo have an operation light on it that lights up when either the control lever is moved or the brake pedal is stepped on..hope this helps..repost findings..

I had this same problem (brake lights won't come on when pushing on brake) I found that the brake light sending unit had come out of adjustment.Look under the dash by the brake pedal.There is a plastic threaded unit that needs to be pushed back towards the brake pedal lever.Careful not to push it to far or the brake lights will stay on. Hope this helps

There is definately something shorted to power through the brake lamp circuit. If you have any aftermarket equipment installed on your Blazer, I would recommend un-installing it. I have seen similar problems caused by aftermarket alarm systems, remote starters, etc.

I DID do a search for possible Technical Service Bulletins (TSBs) for your vehicle. There are many TSBs published for known problems on your vehicle. However, there are NONE that apply to the symptoms you are describing. If this is not being caused by aftermarket equipment, then some serious electrical diagnostics needs to be performed to find the actual CAUSE of the problem. It could be anything from wires that have rubbed together in the wiring harness to an internal fault in one of the computer modules.

e emergency brake cable has to be removed at the pedal on the kick panel and not at the dash pay attention on removal and repeat steps to reinstall as it can be slid in from the front of the dash for new install but has to be removed in reverse steps

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Trailer Wiring Diagrams 4 Way Systems

4 way flat molded connectors allow basic hookup for three lighting functions; right turn signal / stop light (green), left turn signal / stop light (yellow), taillight / license / side marker (brown) and a ground (white).

4 way tow vehicle side.
4 way trailer side.
5 Way Systems

Same as 4 way system listed above but adds a extra blue wire for brake signal or auxiliary power. Used on pop up camper trailers or utility / boat trailers.
5 way tow vehicle side.
5 way trailer side.
6 Way System, Rectangle Plug 3/4 inch by 1 inch 6 way rectangle connectors right turn signal (green), left turn signal (yellow), taillight (brown), ground (white). The red and blue wire can be used for brake control or auxiliary. Use on a small motorcycle trailer, snowmobile trailer or utility trailer. Can also be used as custom wiring on trailers with 3 light/wire systems. See "Tow Vehicle Taillight Wiring" below.
6 way tow vehicle side.
6 way trailer side.
6 Way Systems, Round Plug

Round 1 1/4" diameter metal connector allows 1 or 2 additional wiring and lighting functions such as back up lights, auxiliary 12v power or electric brakes. Note: The black (sometimes red) 12v and blue electric brakes wire may need to be reversed to suit the trailer. Check with a test light or VOM. Uses: horse trailer, travel trailers, landscaping trailer, car trailer, etc.

6 way tow vehicle side.
6 way trailer side.
7 Way Systems

Round 2" diameter connector allows additional pin for auxiliary 12 volt power or backup lights. Uses: heavy duty landscaping trailer, car trailer, boat trailers, horse trailer, travel trailer, construction trailer, etc. Check with a test light or VOM.

7 way RV flat blade tow vehicle side.
7 way RV flat blade trailer side.

check the microswitch on the brake pedal, you should be able to see it under the dash by the peadal mount, if you can chage it or test it yourself then try, but only if you can see the plug/soket join on the lead. If not then ring an auto-electrician & have them test it.
Hope this help's

Replace bulbs, clean sockets, check towing harness, check brake swich under brake pedal. fuses???
Vitally

Sounds like your brake light switch, located on the brake pedal, has gone out. Shouldn't cost to much at auto parts store. Thanks for using fixya.

Sounds like the turn blinker is shorted internally. Suggest you change it out, to test this.

My next check is that no wiring is melted and burned, such as can happen with any connection to tow a trailer. U-Haul has fine print that indemnify them of any problems they cause! have you towed anything recently?