Red97LT1

iTrader: (8)

I can't get the brake light to go off on the dash.I don't think it's the switch,because my DRLs are working fine,they turn on when I release the parking brake. I'll give some info as to what caused it and see if you guys know of anything else to check.

Coming home a car pulls out in front of me and I hit the brakes HARD,immediately the brake light come on and my brake pedal hits the floor.Now I don't have any brake pedal at all,so I carefully drive home.

I checked and found that my master cylinder had failed.I replace it and my pedal is firm. I also bleed the whole system while I was at it,including the ABS block. The brake light stayed on.I bleed the brakes a second time to make sure that there wasn't any air still in the lines and the light still stayed on.

So,what do you guys think it could be?
As mentioned,I have a firm brake pedal and the car stops fine.

If I don't figure it out,I'll just take it to my mechanic and let him deal with it.

ghardester

The brake light in most modern cars will be lit when there is a loss of brake fluid and pressure, as happened when your pedal hit the floor. Loss of fluid pressure lights the brake light as a warning that something is wrong. I do not know if our F-bodies warn in this way, but probably.

I would think that the light would go off after the sensors have determined that you now have fluid and pressure. Like many warning lights, it could take a number of drive cycles for the sensors to tell the PCM that the problem is gone before it turns the warning light off.

I would drive it for 3 or 4 days and see if the light resets before taking it to the shop. You may need the shop to reset the ABS if it does not clear on its own.

wssix99

iTrader: (5)

Here's the killer.... That brake light signals multiple things, two of which are a loss of brake pressure and when the parking brake is on. = brilliant

As I understand it, any ABS codes would trigger the Low Track or ABS lights, which are separate.

I'm sure the loss in brake pressure caused the light to come on in the first place. I'm not sure what would extinguish the light but what a perfect time this would be for the classic parking brake switch malfunction!

That parking brake switch will commonly get dirt in it, causing a break in the circuit similar to when the parking brake handle is pulled up. It might be worth your while to test that switch - the only catch is that you have to take the center console off.

Red97LT1

iTrader: (8)

How would I check the switch? Does it ground itself out when parking brake is released? Can I just ground the wire that goes to the switch to see if it goes off?

Kevin97ss

Most likely the pressure differential valve is stuck. This valve slides and activates a switch when there is pressure loss. Most of the time once the system is fully bled and operational pressing hard on the brake pedal will reset it and the light will go out.

Red97LT1

iTrader: (8)

I did a few hard stops today to see if it would go off,so far nothing.

Kevin97ss

No need to drive the car, with it running press the brake firmly until it wont move any further. If you hear a pop and the light goes out your good. Word of caution if you have another weak spot in the system this may expose it.(ruptured hose, line, etc.)

wssix99

iTrader: (5)

Yes.


Sure, but you'd need to get a hold of the schematic. I assume there is a single lead that goes back to the BCM for this signal.

1 FMF

iTrader: (1)

there is no brake "pressure" sensor.
there is only a fluid level sensor in the master cylinder reservoir, that's what's keeping your brake light illuminated. either the sensor is bad, or you don't have it connected since you replaced the master, or you broke it when replacing the master.
unclip the electrical plug to the master cyl sensor, put a paper clip or equivalent into the 2 prongs making a connection and see if the brake light goes out. also be aware that the wiring going into that plug may have pulled out, so when you are inserting your paper clip jumper you actually might not be making a connection. if you are ok with it you could just cut the wires to the plug then twist them together... i don't know if replacement plugs are easily available.

JOHNNY59

iTrader: (398)

if you want to check the e-brake switch you will have too remove your console top plate. the switch has a single blue going to it.

Kevin97ss

I was responding to the OP using the information in his sig and his screen name both. It's reasonable to believe that the car in question is a 1997. It also seems reasonable that your reference point is of a 2002 model based on the information in your signature.

The 1997 model year used a totally different ABS system which includes a differential pressure switch. It does not include a fluid level switch.

The PDS is the aluminum block on the side of the ABS unit. The pressure switch connector is mounted between the two hard lines.
https://sites.google.com/site/zigzau...BS_module2.jpg