R Mackow

My ABS light came on at the Pocono north course two weeks ago. Went off on the drive home. I reset all the diagnostic codes and the light stayed off until last Sunday when i attended alow spd. autox.
On Sunday I was locking both rears then both fronts and the light came on. The light went out and ABS was working when I left Sunday afternoon. The TCS code was C1226H(LF wheel speed variation).
Last night I pulled the connector at the LF wheel and put some silicon grease on the connector and put it back together. I will rebleed the brakes(I did put fresh fluid in prior to Pocono and bleed the system.)
I have speed bleeders. I am not leaking fluid, but could an ABS light be an indicator of air in the lines? Any tips would be helpful.

davidfarmer

it is most likely a speed sensor going out, unless there is a wire damaged somewhere. Every time I've had a code repeatedly go back to the same wheel, only changing the bearing/sensor fixed the problem.

AU N EGL

R Mackow

Would the speed sensor failure on one wheel also precipitate/initiate the ABS failure that I experienced? I definitely locked up both wheels when the ABS went out.

davidfarmer

if a SINGLE code is set, the ENTIRE ABS system shuts down, and you are totally on your own. You can lock a single, or all 4 wheels, if you brake too hard at this point.

The system need all 4 sensors at 100%, or NOTHING works.

BQuicksilver

As noted, it's all of nothing. You wouldn't want to just lock one wheel.

I had a wire get damaged and freak out the system. Some basic repair work saved me buying a new sensor. Good luck.

davidfarmer

as noted, wires do get cut, but it is usually pretty obvious if you just inspect the wires. I cut one at Rd Atlanta on my current car, and hope that corrects my ABS problems. Even with an obviously damaged set of wires (once found, it was obvious), it still only failed after a couple of laps.

R Mackow

David, Bu, AU:
Thanks. I am going to pull the wheel again right now and check the wiring harness. If all is OK then check for a sensor/bearing. Anybody have GM part number?

davidfarmer

7470571, $220 at Gmpartsdirect.com

davidfarmer

I'm not sure that number is right....check with your dealer or get the repros at NAPA

R Mackow

Thanks for the part no. I checked the wiring. All wiring is intact on the LF senor. Also bled brakes and test drove. ABS light came on. turned car off to fill up at a gas station and light stayed out. With the light on I keep getting messages on the DIC like: service traction control, service ABS, etc.
I'll check my service manual for removal procedure, but it looks like 3 bolt hold the unit in place. The bottom torx(or allen head screw)could be difficult to remove since the lower ball joint stud is in the way. Looks like a lower ball joint removal is req'd. What is the purpose of the allen head in the top of the stud? If i back off the nut to the top of the stud and tap with a wood block will the ball joint drop out?
OR am i all wet. Do i have to put a jack under the bearing bracket and jack up the bracket to lift it away from the ball joint/lower controll arm?

davidfarmer

getting that ball joint is required, and can be difficult. Loosen the nut, but don't remove it, then pop it with a hammer. THEN take the nut off.

The torx head is to hold the ball joint in place, so that it doesn't turn. Not a problem coming apart, as friction will hold it, but putting it back on may spin.

Wait till you have to change a rear. Same procedure but you also have the axle in the way. Took me 45minutes to find my axle nut socket when I tightened mine a few days ago (had lower bolt come completely loose, jammed up against the ball joint nut).

R Mackow

You guys are a big help. Thanks.

Rich

R Mackow

Thanks again. I installed the abs/wheel bearing sat. morning. Would have taken 3 hours, but the crappy(2 pc.) T-55 socket came apart at 95'-#. The top of the ball joint has a 6mm allen socket..had to pick up a socket. The treads of the ball joint and nut need a lubricant. The nut is a jam nut style. Not sure if this was a one-time use nut.

The old abs sensor wire had a break in it where it wrapped around the aluminum housing.