Since Saturday morning my yellow ABS light has been staying on, and also my red BRAKE (1)(2) light.

When I turn the key to on, all lights come on, then after truck us started red brake light stays on without a blink and my yellow ABS light goes out for a split second then returns and stays on constantly.

My brakes appear to work fine...no leaks..firm....stops fine.

This is on my 1994 with a 302.

Should there be a code stored someplace for this ??

Does the red brake light automatically come on when the ABS light does ??

Or is there a significance to both being on ??

Does anyone know.........any ideas ??

Thanks

 

You might just have a bad connection at the master cylinder, the 3 wire connector there on the drivers side of it.

If the connection is weak or loose one or both lights will come on depending on what wires are not making connection.
I found on my truck and my sons bronco II the little spring tab had rotted away, replaced the wire ends and the lights when out.

You can check for RABS codes via the connector under the dash right in front of the glove box. No need to remove the glove box, just behind the bottom edge of the dash itself.

Black with a orange stripe on one lead, solid orange on the other side lead to the connector. Disconnect the connector, turn the key on a ground the blk-org wire for several seconds and the ABS light will flash any codes. If you don't have a manual post the flashes and I'll be happy to look it up for you.

16 flashes is "system operating correctly" RABS II.

 

Thanks danr1, will be checking it a little later.

 

Had the same thing happen to mine, no problems with the brakes and drove it like that for...... well, too long. anyways, I replaced the little sensor on the rear gearbox but the light was still on. Checked the Master cylinder wiring but didn't make a difference. I replaced the Master Cylinder and that finally fixed it. Mine's a 95 EFI 4.9 but it only has a two wheel ABS others have four so if you can ID yours and learn how to troubleshhot it as danr1 recommends you'll be much better off.

 

There is a little fluid sensor in the master cylinder that goes bad all by itself. I think if you jump the brown-brown wires you bypass it (I cant check, I just sold my jumpered harness at carlisle....) but I can go look at a stock one if need be.

 

Yes there is.
ASB Light on =
If a concern is found, the anti-lock electronic control unit will be deactivated and the REAR ABS light will be illuminated.

Red BRAKE light ON with ignition switch ON and parking brake released.

1. Possible Contributing Base Brake Component/Vehicle Wiring Concerns
2. Brake fluid level low in brake master cylinder
3. Wiring between diode/resistor network and anti-lock electronic control unit is shorted to ground
4. Anti-lock electronic control unit module
Worn or damaged brake fluid level switch

 

Got It !!!!

Low fluid level.......................seems my master resevoir is stained from having dirty fluid in it at one time or another and I thought it was almost full. Was low enough to trigger the lights, but not so low that it will need bleeding.

I guess the idiot light saved this idiot a lot of work bleeding.

Thanks all

 

My 93 started the exact same thing - outa the blue.
Brakes work great and no fluid leakage anywhere, no air in the line.

I got a code 4 out of the RABS II unit.

Both the yellow ABS light and the red Brake light are illuminated.

The valve has tested over 10000 ohms on #2 to ground and #2 to #3.
I still have to test the harness circuit.

Will a failed ABS valve or harness set off both the yellow AND the red light?

Is there a way to test the master cylinder switch without just replacing it?

 

my truck does this all the time due to a leak somewhere in the rear brake lines so about once every two weeks i gotta fill my resovour up.

 

Wow mine is doing the same thing and I guess i have to bleed my brakes now since I had NO fluid when I checked

 

i replaced my front lines a few weeks ago due to them blowing out on me and i know they are not leaking so my only guess is the rear brake lines.

 

Just got in from garage. Tested the harness and it meets all of the specifications listed Haynes manual.

Would the next logical culprit be the master cylinder switch?
Best way to test? I hate to just start replacing stuff without verification first.

 

-BUMP-

Is it safe to assume that the switch in the master cylinder SHOULD be closed(continuity between the two circuits poles) when it is operating properly??