So in the last 10 miles or so of my 65 miles home from work i noticed a noise that sounds like an electrical hum/rapid clicking sound, it doesn't do it when im not on the accelerator pedal.... let off and it goes away, hit it again and itll start right back up.... it seems to me that its on the drivers side... so I cant really put my head up under there and see what it is while driving down the road... i also have had park brake light come on and off during this same time period probably 4 or 5 times in that same 10 miles... i checked the park brake pedal multiple times and it is not on at all. never has been really since ive owned the truck.... no need with an automatic.... and the fear of sticking cables.... so i don't know why the light would suddenly start coming on. anyone have any ideas or had this happen before? I'll see if it does it tomorrow on the way into town but id like to get some ideas before then.

 

The dash brake light can be activated by several things. A weak vaccume pump and low fluid in the brake master cylinder along with the park brake are a couple of things to check. On the humming under the dash, I have no clue. May be you have something going on with the sensors on the go peddle.

 

First, that's not the "park brake light". As is the case with every vehicle sold here in the last 50+ years, that's the brake FAILURE WARNING light. There's a reason it's red, and that it has an English word on it rather than just a symbol. Its PRIMARY function is to warn you if you have a hydraulic leak which could lead to complete brake failure. Its secondary functions are to caution you when you lose vacuum for brake boost (you lose power boost, but the brakes don't fail) and when you've left the parking brake applied (you wear the rear brakes prematurely). You should NEVER drive the truck with that light on unless you've confirmed that it is not on for its PRIMARY reason. So FIRST thing to check is your brake hydraulics.

As for the noise, have you tried parking the truck, then getting down into the footwell and revving up the truck with your hand on the go-pedal, to better locate the noise? About the most notable item on the left side down there is the PCM, which happens to be behind the parking brake pedal/release assembly. But it's a solid state device; one wouldn't expect it to make any noise (but with electronics, anything's possible).

The truck doesn't have a chip on the PCM by any chance, does it?

Only "moving" electrical parts in that area that come to mind are the turn signal and emergency flashers, plugged into the interior fuse box.

 

Your truck is a CC right? Make sure it's not the circuit breaker for the rear windows cycling. Pull the fuse panel cover and feel around. If it's that circuit breaker it'll be hot to the touch. It can be a fire hazard, so I wouldn't take it too lightly.

 

Well thanks for the insight on the brake light, I honestly didn't know it served all those functions.... and I do suppose it was indicating low vacuum because on my way to school this morning I lost control of the HVAC system and it switched to defrost and lost power brakes.... vacuum pump bit the dust, luckily the diaphragm went out instead of locking up.... got a new one just waiting to put it on, I'm wondering if the clicking noise I was hearinf had to due with the HVAC loosing vacuum.... it was only happenin at higher RPM I noticed down below about 1500 it stopped.... we will find out this afternoon

 

Good to hear that there's an explanation for the light. Noise could be HVAC associated. Simple test would be to pull the vacuum line from the pump, turn the HVAC controls to OFF, start and rev it up, see if you still get the noise.

Driver's Ed must be a complete joke nowadays. That's where they're SUPPOSED to cover the standard dash warning lights like BRAKE and high beams. Someone started a "what did you learn to drive on" thread over on another car site, and it morphed, in part, into a talk about driver's ed. Dismaying to see what little is covered anymore. I wouldn't have passed if I couldn't demonstrate how to change a tire and jump-start another vehicle. I feel kinda bad for young drivers who weren't put through the paces that our generation was. Pretty soon it's going to be steering wheel, go-pedal, brake pedal, yeah you pass.

 

I do agree there, while I was a technician there are several things I didnt learn... that being one of them... road trucks don't have that light. Neither does the military really. At least I learned it here, just another thing to add to the tool box between my shoulders!