ABS Pissing Me Off

[Big T]

Where I last left off I had taken the '99 Burb in top pull codes for the ABS. Codes indicated the RF sensor did not have conductivity, or basically was out. I replaced the sender and the ABS worked for a couple drives before the ABS light came on again, basically staying on since then. Typically, the ABS light comes on after I start rolling forward after starting up.

Had the Burb out on a road trip this week. We were doing some off roading in the desert and I noted the ABS light was off. Sure enough, ABS was working, this was over several miles of rough driving. When I got back on the pavement, I said aloud "it typically takes a couple seconds and the ABS light will come on." This time it took about 10 seconds for it to come on and it stayed on the rest of the trip, which was about 1,200 miles, mostly highway, with some off roading.

Obviously, the ABS pump works when the light is off. Senders on both sides have been replaced twice. Bearing have about 12K miles on them. Desperately would like to figure this out. If it's not the senders, then is it in the harness going to the ABS pump? If so, how do I test for this?

 

[6.2 turbo]

You have to watch the readings on a scanner. Sometimes,one sensor will start reading at a higher mph than the other. Sometimes it can be corrected,by removing shims on the sensor.

 

[Big T]

The only scanner I know that can read the ABS codes is at the dealer. It's $100 to plug it in and I don't get to watch it. New senders are $30. I was not aware of any shims for the senders.

 

[WarWagon]

The power for the ABS unit comes from the driver's battery cable on 1995. Your 1999 is worth looking at positive power for cable corrosion and the ground for it.

I suggest have the dealer fix it. Otherwise find a shop that can read ABS codes other than the dealer. You are dealing with electrical and need to know when the condition is present including results of wiggle testing. Wiggle testing is moving the wire to find the intermittent bad spot.

I would start to look at the rear sensors as well.

 

[Big T]

The power for the ABS unit comes from the driver's battery cable on 1995. Your 1999 is worth looking at positive power for cable corrosion and the ground for it.

I suggest have the dealer fix it. Otherwise find a shop that can read ABS codes other than the dealer. You are dealing with electrical and need to know when the condition is present including results of wiggle testing. Wiggle testing is moving the wire to find the intermittent bad spot.

I would start to look at the rear sensors as well.

I will check the power and ground cables. Last time I looked they were fine. I've done the cable mod and it's been starting fine.

Rear sensors? Didn't know they even had them. When I last took it in for this, the code was for a fault in the RF sensor, which I've since replaced. I'm wondering if the harness from the sensor plug to the ABS unit is bad? How would I test that?:

If I have to take it into the dealer to get it fixed, then I'm just going to have to live without it. I recall the one time I had them work on it, it was $270 for installing a front wheel sensor. I can do that job in 20 minutes and the AC Delco part is $30.

 

[Big T]

Here's my previous attempt with the dealer pulling the code:

Are you talking about the wires connected to the sensors or the harness the sensors plug into? I took my '99 to have codes pulled and it showed a circuit fault with the RF sensor, sonI replaced it. The ABS has worked intermittently. The light will typically come on when in reverse and wheels turned. In the rare cases that it does not come on, it will stay that way for that trip with the ABS working. Both wheel sensors are near new with the bearings and the RF has been replaced again after the bearings. Very frustrating as I want it to work in the snow.