2nd Gen Non-Engine/Transmission ABS fault at slow speeds

[kbryan]

Have a problem with ABS on 2001 quad. Brakes work fine until speed drops to below 10 mph then abs kicks in and lose braking. If you take your foot off the pedal and press again brakes bite again. I have replaced the rear wheel sensor and have no abs light showing.



Any help would be appreciated.

 

[Jim S]

I had the same problem and the dealer replaced the right front speed sensor.

Now the problem is back after 2 months an I am going to replace the left one myself and see how it goes. I pulled the fuse for abs to fix the problem but that kills the speedo and odo.

 

[Johnny5]

Are you getting fault codes? Just checking as I have a similar problems but I do not get any lights or codes. After checking the TDR and hearing of others with the problem, I 'm planning to what others have suggested to clean the sensor and the part of the wheel hub that triggers the sensor.

 

[fest3er]

I believe that the CAB (Controller, Antilock Brake) is seeing the voltage from the rear sensor drop below the minimum threshold, thus causing it to think the rear wheels have suddenly stopped turning; thus ABS is engaged. In a properly functioning vehicle, the speedo drops out around 3-2 MPH, and the CAB is programmed not to engage at such slow speeds.

The only way to tell for certain is to connect an oscilloscope to the rear sensor and ensure that it is putting out at least 2V (I think) at slow speeds. As the speed increases, the voltage increases; this is why the brakes work fine until a certain low speed.

If the rear sensor is OK, then you need to check the voltage at the CAB itself. If the voltage is low, you probably have a problem with the twisted pair wiring between the CAB and the sensor. If the voltage is OK, the CAB might be faulty, or the connection(s) might be faulty. One other thing to check is the ground from the CAB; make sure it is in fine fettle.

I figured all this out when I was playing with my Abbott speedometer/odometer adjuster, trying to get it to work between the CAB and the PCM. I finally gave up and bought a TruSpeed unit, which has been working great ever since; the speedo and odo are less than 1% off, as measured via 100 miles on the highway.

 

[Jim S]

No I don't throw any codes. I will follow the troubleshooting fest3er suggested and see what happens.

 

[Houser]

Some times front wheel bearing wear will cause the ABS light to come on.



Houser

 

[JoeBioDiesel]

If any of you guy can get your hands on a scanner, check the data from the ABS controller. Watch the wheel speeds and come to a slow stop. You will quickly see which sensor is dropping out first and be able to replace it. Spending a few bucks at a local repair shop to have it checked out is a lot cheaper than replacing an incorrect part.

Joe