Chevy & GMC Vans

After putting up with a C0223 code for a while (intermittent right front wheel speed sensor) I cleaned the sensor head mounting boss like the service bulletin said, on left & right sides. Did not help. Picked up a pair of front wheel speed sensors on eBay, installed them, no codes set, but the ABS activated on every stop. Jeez. I did the check per the service bulletin - VAC output when rotating front wheel by hand - should be able to get 350 mV AC , could barely reach 100 mV ln one, 50 mV on the other. Basically, crap sensors. My van is AWD - with both tires in the air, it is easy to rotate one, the opposite side just goes backwards. So, now negotiating with seller, and you can bet that before I snug things up, I will check the "new" sensor output. On the bright side, I can R&R both sides, and do the checking, in less than an hour and a half.

In my experience, when the front ABS sensors start to fail on an AWD, it is time to replace the hub bearings. The only way they get dirty is from the grease in the sealed bearings breaking down and eventually you will have some fine metal particles as the bearings come apart.

The right front sensor was intermittent electrically. The resistance bounced around when I wiggled the cable. Your point about the front hubs is well taken. I am considering a full brake job (78000 miles) and wondered about replacing the hubs at the same time.