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ABS and brake warning lights

Discussion in 'Repairs, Maintenance, Help' started by NYBo, Oct 23, 2017.

  1. NYBo

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    I am getting intermittent ABS and brake warning lights. No apparent problem with brake function. I was thinking the most likely cause would be the rear ABS sensor on the differential rear-wheel only ABS), but it dawned on me that the brake light comes on first. Could it be the sensor for the regular brakes tripping both lights? I haven't scanned for ABS codes yet; my old Actron doesn't have that capability.
     
  2. CudaPete

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    Check your owners manual. IIRC the manual for my 02 GC says this is a software issue and the vehicle is not safe to drive. Been a while so best to confirm this is the case for an 07.
     
  3. AllanC

    AllanC Well-Known Member

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    You did NOT indicate the specific vehicle that is having this issue with ABS and brake warning lights. Vehicles today have 4 wheel antilock braking system with a speed sensor at each wheel. So most likely the problem is an incorrect / no signal for 1 or more wheel sensors, a problem with the hydraullic motor pump within the ABS unit or a wiring problem ( short to ground or open) to any of these items.

    When an ABS fault is detected many times the BRAKE warning lamp gets illuminated also. It means that the ABS function is disabled but the power assisted, hydraulic braking function is still functional. You do need to get a diagnostic fault code readout to point you in the proper direction to resolve the problme.
     
  4. AC TC

    AC TC Well-Known Member

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    It can both, either its a abs specific problem or a problem in the brake system that keeps the abs from working.
    - low level of brake fluid fex.
    Have it scanned, these systems can be costly to fix by the guess and replace method.
    Usually its something simple.
     
  5. NYBo

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    It is the vehicle in my signature. Rear-wheel only ABS.
     
  6. AllanC

    AllanC Well-Known Member

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    That surprises me as I would have expected no antilock brakes or 4 wheel antilock; not something in between. Since the rear wheel ABS speed sensor is on the differential, you could remove the sensor and clean any metal fuzz that has accumulated on it. That might be the problem but is only a guess.

    You can check the wiring and make sure all connections are clean and tight. But without having knowledge of a specific ABS diagnostic code, you are only guessing. Fastest and most definitive solution to the ABS problem is to get any diagnostic codes retrieved and then determine a direction.
     
    Doug D likes this.
  7. valiant67

    valiant67 Rich Corinthian Leather
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    Rear wheel only ABS was pretty common in the pickup trucks, from around 1989 until, I assume, they went to 4 wheel ABS recently.

    I agree - the speed sensor is about the only effort I'd put into it without scanning for codes. That sensor was a common, inexpensive problem that would often light both the ABS and brake warning lights in earlier trucks.
     
  8. Doug D

    Doug D Virginia Gentleman

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    I have a similar truck - 2006 Dodge Ram 1500 SLT RWD and have had the brake/ABS lights light up on occasion. I have not chased the issue since it is very infrequent. I surmise it's probably the sensor accumulating debris on it. If the lights do come on, I'll pull over and turn the engine off, and restart, then put it in reverse and back up about 10 feet. Sometimes, but not always, this will turn the light off. Either way, the brake/ABS lights will eventually go out.

    As I recall rear ABS is more or less mandated or at least standard for pickup trucks since they are so light in the rear. Most of a pickup's weight is in the cab/engine area. The rear wheels have a tendency to almost lose contact with the pavement under moderate to heavy braking and light load or no load conditions. This can result in spin outs.
     
  9. valiant67

    valiant67 Rich Corinthian Leather
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    Rear wheel ABS replaced the height (basically weight) sensitive proportioning valves Chrysler used on the back of pickups and minivans.
    I don't know how other manufacturers did it, but my 1987 Dakota was much more surefooted braking without wheel lockup, loaded or empty, than a Ford Ranger. The only problem was the height sensitive vales would corrode and you'd lose rear braking power. Rear wheel ABS was a great fix. Dodge made a big deal about the rear antilock on its trucks when it became available around 1989 or so.
     
  10. CudaPete

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    OK, so I checked my 02 GC's Owner's Manaul and my memory is not that bad...yet. It says if both the Brake light and ABS light are on this indicates that the Electronic Brake Distribution System (EBDS) has failed and immediate attention is required. Don't know if this applies to your truck but you may want to check the Owner's Manual.
     
  11. NYBo

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    I checked my manual. Fortunately, no such dire warning. It says an ABS fault will trigger both lights. Kind of silly, if you ask me.
     
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  12. valiant67

    valiant67 Rich Corinthian Leather
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    The trucks used a different “logic” than other vehicles. They lit both warning lights when the fault only affects the ABS system. Usually you see the brake warning light and expect a fault in the hydraulic system.
     
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  13. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    My 92 Dakota will also illuminate both lights if I blow the fuse for the brake lights. I found that out once when pulling a defective U-Haul dolly.
     
  14. ImperialCrown

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    The red BRAKE indicator is more severe telling you that foundation brake (hydraulic, mechanical portion) operation may be affected by the particular fault. The yellow ABS lamp warning is less severe, indicating that you may not have ABS operation, but that the foundation brakes are still operational.
    With an unloaded truck, the rear brakes are more prone to lockup on a wet or slippery surfaces before there was standard ABS. As ABS may be more critical for safety in a RWD pickup or van may be why both red and yellow warning lamps are lit.
     
  15. bguy

    bguy Well-Known Member

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    Don't forget there's a sensor on the front end.
     
  16. ImperialCrown

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    A 2007 Ram 1500 4WD should have front and rear, not rear-only ABS.
    Your wheel speed sensors should be mounted at each wheel hub. Only the 2500/3500 models had the differential case-mounted speed sensor.
     
  17. NYBo

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    Nope, rear-only, with one front and one rear sensor, the rear being on the diff. It may be an odd duck, but that is also what the build sheet says. Perhaps because my truck started life in Canada?
     
  18. AllanC

    AllanC Well-Known Member

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    Where is the front ABS sensor located?
     
  19. NYBo

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    Front left wheel.
     
  20. ImperialCrown

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    This differential and LF wheel speed sensor for ABS doesn't make sense to me and it isn't what the factory 2007 Ram 1500 service information is showing.
    Perhaps you should get the ABS fault code(s) next?
     
    AllanC likes this.

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