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07-31-2009, 03:24 PM #1
- Join Date
- Jul 2009
- Owego, NY
Anti lock brake pulses at low speed
I have an '03 Silverado 2500HD, 4WD Crew Cab, Diesel w/6 spd manual transmission with about 27K miles. For some time now (and I'm embarassed to say just how long) I have had a problem with the front brakes pulsating rapidly every time when I stop. During braking, everything seems normal until the vehicle is almost stopped. Then, the rapid pulsating begins until it is completely stopped at which point the pedal then fades quite a bit (but doesn't go all the way to the floor).
Now that I'm getting ready to start towing a camper trailer, I decided it was time to fix this "problem".
While installing new rotors & pads, I decided to check out the ABS wheel sensors. I pulled both the left and right front wheel sensors and everything looks good (no water or rust down inside the hub area). After re-installing the sensors, I disconnected the C2 connector at the EBCM module so I could make some readings back to the sensors. Both sensors read about 1K ohm at the C2 connector, which is well within the value spec'd in the service manual.
Next I made AC voltage readings while spinning the hubs by hand. The left sensor produces about 100mV AC which is exactly what the manual says it should be. The right sensor however, produces about 350mV AC.
Now comes the confusing part. The manual says that if you get over 100mVolts, that you either have
(1) a bad connection somewhere, or
(2) the sensor is bad.
I've worked with electronics for over 40 years and I'm having a hard time understanding how (1) a bad connection can give you too much of a voltage reading or (2) how a sensor with a normal resistance reading can put out too much voltage.
Could some of you high tech guys weigh in on this one please? Could that high output sensor be the real cause of my problem or couldn't it really be that simple? Thanks, DSLVOLKS
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