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1996 Oldsmobile Ciera - Red Brake Light On

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  • Keiths1976
    replied
    Here is what I would do for the last hoorah pop those wires off near the battery on the radiator support sand them bare on the Metal and sand down the wire clamp thats round . Put some electric grease on it and re tighten . You will never find another one but a junk yard one which is a gamble brakes will work fine regardless

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  • Slacker
    replied
    I double checked the 3rd brake lights. All are in working order. I also checked the ground by battery, those all look good as well. I re-bled the brakes again and the pedal feel is now completely firm while driving.

    My friend had a code reader that says it can read ABS codes, but when we tried to connect it, it just kept failing to connect to the ABS module.

    At this point, I decided to bring it to my mechanic and see what he thought. He confirmed the brakes are completely fine. Double checked the master cylinder and the ebrake. Both also were in order. His scan tool was able to connect to the ABS module and it light up with at least 10 different error messages. He concluded the same as you that the ABS module has most likely gone bad and is causing the red brake light to illuminate as well. Seeing that the car is over 25 years old, it passed the safety inspection and I can pretty much just ignore the warning lights if I want and live without ABS.

    I guess that brings this to a close for now as the ABS module, like you said, is expensive and I probably won't be able to any time soon. Thanks for all the help.

    I also noticed a blown fusible link, but I'll make a separate thread about that.

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  • Keiths1976
    replied
    No honestly a better scanner can get into the pcm the wiring is all on the data link under the drivers side and abs wire is there as well . Some scanners can access it some can?t pending what they can read obd 1 cars a-body 94-5 were not paper clip methods even obd1 and needed a scanner to read anything . But I feel you are on a direction with the brake light but first thing is the abs code . When I said with the fuse u hard reset the system and it will self prime . Also there is 2 ground wiring on the drivers side near the battery on the radiator support . If that is corroded any way on the black wires u could be having a ground short abs abs light brake light is on . . It?s hard to do any real testing with out a scanner on obd2 . Here is one more thing for the 96 I had my 95 have bad third brake light bulbs would throw the abs light on too I think we covered the brake lights earlier on this chat not sure I mentioned the third brake light . Just pray man it?s not the abs master cylinder assembly having a major issue . That would show up on the scanner as a failure . Only junk yard 95-6 cars u have to take one off there is no new anymore that I heard of nor 400 bucks either

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  • Slacker
    replied
    Thanks. I'll double check the wiring when I take the wheels off to get the tires replaced.

    My code reader can only read engine codes, not the ABS codes. Is there a way to check them without the scan tool, like you could with ODB-1 and a paper clip or something?

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  • Keiths1976
    replied
    Since a 96 and obd2 u should be able to read the abs code . I wouldn?t cheap out I picked up timken wheel bearings few years back . I have one gm stock wheel bearing that was fine with 199k on it I only changed to the timken cause I was doing brakes and already had half apart so I did . To be on the safe side check your wiring that goes to the abs wheel speed sensors to make sure my accident it was snacked or cut moving the caliper around

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  • Slacker
    replied
    I found the dash schematic from this thread: https://www.a-body.net/forums/showth...clusters/page2


    It looks like the only things on there besides the brake control module are the brake fluid level switch and the parking brake switch. So, I guess that would make sense if that control module can turn the light on. I'm guessing the lamp is getting its ground to turn on from that?

    This is the part you're saying needs to be replaced, right? https://www.rockauto.com/en/catalog/...ing+&+hub,1636
    Any idea how much of pain they are to swap out? It looks like it might just be bolt on instead of needing to be pressed? I figure I should do both sides in the front.

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  • Keiths1976
    replied
    U have a wheel speed sensor issue if that abs stays on 9-10 front wheel bearing /abs ring

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  • Slacker
    replied
    No luck with the fuse. When I pull it while the car is running, the brake light and the headlights go off but the ABS light stays on. As soon as I plug the fuse back in, it turns the brake light back on.

    I'm not able to test the panic stop because some jerk popped both tires on my one side one night while it was parked on the street and I need to order new ones. I don't remember it pulling after replacing the brake stuff earlier in the year though.

    Hopefully, in the next week I can try and re-bleed the brakes again.

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  • Keiths1976
    replied
    The 96 a body cars have the same abs system at 93-5 . If the car stops firmly not pulls to the side upon 35 mph panic stops. The system is complete even pressure . The light then is electrical issues clean them out with the fuse I stated . Shoot me a email mx67627@aol.com

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  • Keiths1976
    replied
    The system way back in the day shops use to gravity bleed them and be done others used the tech 1 scanner to prime and bleed them . Last option for the obd1 a-body cars was someone key on key off and they bleed the back brakes which cause the rear drum brakes to prime first . But all that took longer with the key on off method . But for giggles pop the rear drums off and make sure no wheel cylinders seals were popped or torn and the light is detected cause pressure is being loses soon first key on priming the abs system .

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  • Keiths1976
    replied
    The abs light could steer u in the right direction unless that?s key on only . Also the master cylinder /abs module attached are one unit . For giggles there is a fuse for the pusher fan in the fuse box labeled that has a power source to the abs pump and relay . I?m starting to thing you are throwing a code in the abs that is leading to your brake light . Even wheel speed sensors for the abs will throw both on . I?d find the pusher fan fuse top upper right on the 95 Buick century it?s there for yours . Pull it while the car is running then pop it back in the abs pump will click prime the check engine light abs light and brake light will go out . You just cleared the codes in the abs then see if it comes back on . Also when you bleed them did you ever run the master cylinder dry or below the brake light switch and it?s a hard code stored in the abs system .

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  • Slacker
    replied
    Originally posted by tlc1976 View Post
    I don?t have a 96 diagram. But on the older cars the light was controlled by analog switches. I wonder if maybe on the 96, the switches might just feed the ECM with the light controlled by the ECM.
    After today, I'm starting to wonder the same thing...

    I took the ebrake switch out to inspect it and reassemble it after I managed to pull it apart the other day. Switch is in good condition. Fiddled around with it more to see if it would do anything with the light but it didn't. I tried grounding and lifting the ground as that seems to be how it works with the screw that attaches it to the car.


    Tried again plugging/unplugging/shorting the connector for the level sensor. Sensor circled in red, connector is in my hand on the right. No luck.



    The brake pedal itself has these three plugs associated with it. I tried pulling them off one by one to see if there was any change. There wasn't on the dash but after I pulled the last one off, the rear brake lights no longer worked until I plugged it back in.


    Those look to be these:


    Checked the wiring harness in the trunk as well as the connector. It all looks good. I think me unplugging it today was the first time it was ever unplugged. Car dies right away if you try to start it with the harness unplugged. I'm guessing one of the wires goes to the fuel pump or something?


    ...and just for the heck of it, here's the dash light.


    One interesting thing that I noticed today was that the brake light is on at key-on-engine-off, turns off while cranking and then about 1/2 a second after the car starts, the light comes back on. When I short the level sensor connector that goes to the master cylinder, the light stays on without the brief pause of turning off. I figured I would mention it in case that helps.

    Thanks for all the help so far!

    Edit:
    I wonder if maybe this might be why the issue didn't clear up with the brake parts getting replaced and lines bled? When I bled the brakes, I did the traditional farthest away from the master cylinder in the back and then went from there. (Passenger rear, driver rear, passenger front, driver front).

    Originally posted by https://www.autozone.com/user/repairGuideContent/2582801579/0996b43f80393816
    Prior to bleeding the rear brakes, the rear displacement cylinder must be returned to the top-most position. This can be accomplished using the Tech I scan tool or equivalent, by entering the manual control function and applying the rear motor. If a scan tool is unavailable, bleed the front brakes. Ensure the pedal is firm. Carefully drive the vehicle to a speed above 4 mph to cause the ABS system to initialize. This will return the rear displacement cylinder to the top-most position.

    I wonder if I have an uneven pressure between the front and rear lines due to not following the instructions above that's maybe causing the light to go on? I would think bypassing the switch would cover that unless it's looking for a specific resistance or something when in the correct range.

    Originally posted by https://www.autozone.com/user/repairGuideContent/2582801579/0996b43f803938ed
    All dual circuit system uses a switch to warn the driver when only half of the brake system is operational. This switch is located in a valve body which is mounted on the master cylinder. A hydraulic piston receives pressure from both circuits, each circuit's pressure being applied to one end of the piston. When the pressures are in balance, the piston remains stationary. When one circuit has a leak, however, the greater pressure in that circuit during application of the brakes will push the piston to one side, closing the switch and activating the brake warning light.
    Last edited by Slacker; 05-07-2021, 05:49 AM.

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  • tlc1976
    replied
    I don?t have a 96 diagram. But on the older cars the light was controlled by analog switches. I wonder if maybe on the 96, the switches might just feed the ECM with the light controlled by the ECM.

    Leave a comment:


  • Slacker
    replied
    Thanks for the suggestions.

    I checked all the rear brake lights and all bulbs light up when the brake is pressed.

    I checked the ebrake switch behind the ebrake pedal. Where the pedal is in the full up position does put the switch in the "clicked in" position. I clicked it on and off with my hand and didn't see the light change on the dash.

    I tried unplugging the connector on the side but it was stuck on pretty good. When it did come loose, the whole connector popped out from inside the switch.. which I guess would be like unplugging it in a way. No change with the dash light.

    The car does have abs but that's a different dash light.

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  • Keiths1976
    replied
    How about this check all the third brake light bulbs and brake lights them selves . Sometimes u get corrosion on the bulbs sockets and will create a short and cause the light to come on . Being a 96 car she most likely has abs . U can pull the negative off the battery for a few minutes and then hook it back up see if that clears it out . Also since abs stores the codes of there is a brake related issue abs light comes on as well . Brake light switch wouldnt really kick the light on but the light bulbs to the third light and back rail light bulbs can . Have a 95 that did this crap and turned out to be a corroded bulb socket . Also the drivers rear inner wheel well in the trunk has the harness for the rear tail lights take a look and see if there is corrosion . Basically shorting that out

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