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Did the problem come about suddenly after some event ???
Check the under hood brake master cylinder reservoir fluid level, if low, it'll turn the brake warning lamp on. If fluid level is ok, give the master cylinder reservoir a thump or two, to make sure the float isn't stuck. Wiggle the electrical connector to see if its loose or has a faulty electrical connection, if so, remove the connector & check for corrosion, bent pins, spread sockets, faulty wire crimps to them, or a ground loop problem from a corrupt in cabin system ground point. A bunch of beginning thoughts that came to mind on this few clues, vintage ride, trouble shoot, let us know what you find.
Ok good feedback, so lets think about this some more. If the things mentioned check out ok, the truck to trailer light pig tail connector & wiring have earned a spot on the suspect list, especially if it's an aftermarket part.
Your 94 4X2 4.0L likely has RWABS & if so, low master cylinder brake fluid level, or a sticking float could turn the ABS light on also.
To further trouble shoot, if the problem came about After hooking up the trailer, disconnect the trailer plug & see how it goes.
If the problem came about After backing in too far, or after installing the trailer connector into the truck wiring harness, disconnect the pigtail from the truck wiring harness & see how it goes. More thoughts on how to maybe isolate the trouble area. Let us know what you find.
As far as the brake light, maybe your e-brake isn't fully disengaged or the switch up in there is faulty. If your brake fluid level isn't low, try disconnecting the plug going into the master and see if the light goes away.
Like PawPaw said, you most likely have ABS on the rear. Perhaps the sensors at the wheels in the back getting wet from your boat launching caused some problem.
I think so. Anyway I had some time today, weather too bad to go fishing, so I looked into it. The master cylinder was 1/2 full so I didn't think that was the problem but.... I raised the float with a stick and the lights went out. You were right about the low fluid, thanks. I have a code and I think it was the MAF needed cleaning and I cleaned it with the right stuff and the code didn't go away. I forgot what I short to get the codes. I'm old and forgetful. Alex
as I was tinkering and testing something today, I purposely pulled my abs fuse in the engine compartment and both my abs and brake warning lights came on. Could it be as simple as a blown fuse?
The master cylinder was 1/2 full so I didn't think that was the problem but.... I raised the float with a stick and the lights went out. You were right about the low fluid, thanks. I have a code and I think it was the MAF needed cleaning and I cleaned it with the right stuff and the code didn't go away.
That’s a lot of fishing mentioned. Either you’re retired or a pro fisherman. Maybe both?
As you now know, your truck would have rear wheel abs as a minimum. Glad you got it solved. Abs is on a different system with a separate test port from the engine so you wouldn’t get brake light codes from the engine computer. Post the fault code for the MAF sensor. You couldn’t then clear the code to see if it returns.
Originally Posted by mfp4073
as I was tinkering and testing something today, I purposely pulled my abs fuse in the engine compartment and both my abs and brake warning lights came on. Could it be as simple as a blown fuse?
Turning on the red brake warning light caused by a loss of fluid or electrical failure automatically triggers the ABS light showing that the system is disabled.
Lets think about all of this some more. The braking system is Sealed so doesn't consume fluid, so if the fluid level is low enough to cause the warning lamp to come on, something else may need inspection. Like worn brake shoes or pads (as the pads & shoes wear, the brake pedal & master cylinder fluid level will naturally drop, so when you put in on a steep boat ramp, it could trigger the float to turn the fluid level warning lamps on), weeping / leaking wheel cylinders, or calipers, or lines, or fittings to them, or a dry-rotted leaking brake booster diaphragm. To check the diaphragm, loosen the vacuum line to it & see if its wet inside with brake fluid.
On the recurring ABS question, on newer models the Rear ABS speed sensor was moved from the tranny tail shaft to the top front center of the rear differential housing, one wire up to it from the drivers side of the axle, in a protective black split wire sheath. The speed-o, ABS, auto tranny & cruise control all use this sensors PID output to do their thing, so you have one. More thoughts for pondering.
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