need help abs and tt4 lights stay on

[gerry]

hi new to hummers i have a 99 h1 and the abs and tt4 light stay on any ideas what is wrong thanks in advance

[Axleman]

The first place to look is at the wheel speed sensors. They are located on the hubs and should be near the tone ring on the halfshaft (the silver gear looking thingy.) If the sensor has moved away from the tone ring, it cannot generate a signal for the ABS computer and you get a warning light.

It could also be a broken wire inside one of the harnesses that go to each sensor.

If it isn't one of these, then be ready for $$.

[CONRAD II]

Its been raining like crazy here and I drove through a ton of water that went up to almost the bottom of my doors. The abs light and tt4 lights came on and are staying on. I'll chk the fuses and wheel speed sensors tomorrow, any other ideas.......?

[M. Grogan]

So is the sensor actually the gear or the small device that is mounted near the gear? I thought that the small device pointing at the gear was the sensor. Anyway, can you visibly notice when the gear pulls away. All four of mine seem to be in the same place and dont move in and out very easily. Sorry for the confusion but can someone break it down a little for me so that I can eliminate the sensor "sliding out". Thanks again. MG

[adamk85]

the sensor is the piece that points at the ring on the axle shaft, you need to pull codes before just replacing parts as the sensors are about 150-180 a piece and can be a pain to remove. pulling codes is kinda tricky to decipher but is a big help in diagnosing, saves lots of $$$.