False ABS Activity On Econolines

[Keith Browning]

Last month I had three separate E-seies come in with various braking complaints that all boiled down to false ABS activation as best as I can determine. I know this by road testing and at different times I would get the ABS clicking in the pedal and maybe a brake pull on one truck and nothing on the other.

 

These were two 2006 and one 2008 model years and only one had RSC, all had 4 wheel ABS.

 

I performed all of the required checks on bearing looseness, sensor and harness damage, tone rings, so forth and so on. One thing that strikes me as odd is that in all three cases I road tested with either IDS hooked up or the VDR. Made recordings on all three during the events. Both tools failed to show a sensor dropping out, valve actuation or pump activity.

 

Anybody run across this?

[Brad Clayton]

Can't say that I have. Any idea what the speed was when the event occurred? You probably already do this, but I always drop the sensor speed range down from 99mph to around 20mph so I can get a better view of any glitches in the signal.

[Keith Browning]

The concern is intermittent. I can experience this coming to a stop on a slow turn or 30/35 MPH driving straight and just lightly applying the brake and immediately I get the "ABS" activity and then it might not happen again for 20 minutes.

 

It is perplexing that I cannot seem to pick it up with IDS at all... and no, i never thought to change the parameter setting though I still think I should be able to see something. These are very short events and I made several recordings between the vehicles. If I get to see one of these again I will try using the shops IDS and VCM which are brand spanking new. Perhaps that is the key. It might also be that I have every freaking PID selected looking for whatever it is. I just want to identify what wheel it is that is triggering this. If I am going to throw parts at something I want to try and narrow it down if I can and maybe even define the root cause.

 

Imagine that.

[Bruce Amacker]

I don't know how those sensors are set up- can they be rust jacking? It's common on GMs to have dry-road-ABS-activation from that.

 

Gas or diesel- how about bad ig coils?

 

On IH's if no failures are found they'll run an overlay harness to the ABS sensor.

 

[Matt Saunoras]

I see this on Rangers from time to time. On the affected wheel I can watch my wheel speed sensor pid drop to zero well before the wheel is done spinning BUT if I actually get the vehicle to false activate it doesn't show anything. It's like a big long data skip that results in no obvious fault when looking at a recording.

 

It has never caused a problem yet because I can always identify the bad sensor when the vehicle isn't exibiting any symptoms. Just weird

[Mbl35]

I had this a few times and every time it was a bad tooth on the exiter ring. I pull the dif. Speed sensor and turn the dif until I feel a chipped tooth. I found that even the slightest chip can cuase it intermitantly at low speeds,

usually under 15mph.

[Alex Bruene]

When I am diagnosing an ABS "misfire", I let go of the steering wheel during the event, and watch the way it moves. If the wheel turns, the front wheel on the side opposite of the direction the wheel turned is the culprit. If the wheel doesn't move, chances are it's the rear