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Brake idiot light flashes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Catman, Nov 3, 2004.

  1. Catman

    Catman Registered Member

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    The other day the fuse for the gauges blew. I replaced it and the brake light stayed on even when the parking brake was released (although it dimmed slightly.) Tonight it started flashing on and off. The brakes work fine and the fluid level is good. What gives?????? P.S. It's a 90 K5/forums/images/graemlins/confused.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  2. trikstark5

    trikstark5 1/2 ton status

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    Is your emergency brake pedal all the way up? Sometimes if the cables aren't tight enough, it will bounce around making and breaking the switch.
     
  3. dremu

    dremu Officious Thread Derailer Premium Member

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    Antilock brake computer is pissed about something. Count the blinks -- should be (for example) eight long ones and then one short one, or maybe the other way around (short ones then long.)

    This example is code 81, which as i recall means the antilock actuator is messed up, and you should give up.

    90-91 K5's and Burbs had RWAL, Rear Wheel AntiLock, which is bloody worthless IMHO. (Only in 2WD, btw, so you're safe in 4WD.)

    -- A
     
  4. dave_90_blazer

    dave_90_blazer 1/2 ton status

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    unplug the abs box next to the master cylinder, light will go away(so will abs, but it didn't really work too good when new)
     
  5. dremu

    dremu Officious Thread Derailer Premium Member

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    [ QUOTE ]
    unplug the abs box next to the master cylinder, light will go away(so will abs, but it didn't really work too good when new)

    [/ QUOTE ]

    Amen! This is what I did -- carefully taped up the connector, so it won't get goo in it ... but the front brakes handle the majority of the load anyway, so who cares about RWAL?

    -- A
     
  6. Catman

    Catman Registered Member

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    Well, I finally got my head out of my arse and guess what? 9short blinks and one long mean the VSS unit on the tranny is toast. LMC Truck lists this little item at $150.00!!!!!! Seems a little steep for having a worthless ABS. I guess I'll unplug the unit at the MC so I can go back to watching traffic instead of the damn flashing lights (except for the ones behind me!) Thanks for the info, folks. /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  7. ncbloodhound

    ncbloodhound 1/2 ton status

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    [ QUOTE ]
    Well, I finally got my head out of my arse and guess what? 9short blinks and one long mean the VSS unit on the tranny is toast. LMC Truck lists this little item at $150.00!!!!!! Seems a little steep for having a worthless ABS. I guess I'll unplug the unit at the MC so I can go back to watching traffic instead of the damn flashing lights (except for the ones behind me!) Thanks for the info, folks. /forums/images/graemlins/thumb.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif

    [/ QUOTE ]


    I had the same thing happen to me a couple weeks ago. It just ended up being a loose connector for me.
     
  8. dyeager535

    dyeager535 1 ton status Premium Member

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    If you pull the VSS connector, you lose the speed input to the ECM, and your speedometer.
     
  9. Catman

    Catman Registered Member

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    Do you mean pull the connector at the box by the master cylinder or on the tranny? The switch on the tranny seems to be the culprit but the speedo /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif still works.
     
  10. dyeager535

    dyeager535 1 ton status Premium Member

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    There is no switch on the tranny. It's a sensor that "reads" the revolutions of a toothed ring on the output shaft of the transfercase.

    If your speedo reads correctly, then I don't see how the VSS itself can be an issue...electronic speedometer and the ECM use the same sensor to determine vehicle speed.

    However, the DRAC could be a culprit, which is what interprets the signal from the VSS before it gets to the speedo and ECM...it "divides" the signal at that point, so there could be an issue with the DRAC. In any case, I've never dealt with the RW ABS setup, so I'm not sure how the ABS interacts with the VSS/DRAC/ECM, or what relationship, if any, they all have.

    I would expect ABS to be tied into the VSS and DRAC, but I'm not certain. At least one person on this board has a 90-91 wiring schmatic online, that might help figure it out.

    Since the "problem" seems isolated in the ABS system, and I misread your post, (thus the longwinded stuff above lol) unplugging the system at the MC more than likely will solve the issue.

    IIRC, the ABS uses a seperate computer to control it, I'm curious to know if that is another thing that the DRAC is tied into, or if the ABS is entirely standalone.
     

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