ABS Traction Control Problem

[lecroy]

I have an 06, 4.6L less than 18,000 miles on it. Was stored in a garage. Bought it used with a known problem with the ABS/traction control.

The ABS, traction control and power train lamps all come on once the car get above 30 or so MPH. They may go back off and come back on at random. If the car is started, running, in park, I can activate/deactivate the traction control fine.


Hooked up the scan tool and it was reporting the left rear wheel sensors was not reading correct. Driving around I can see the speed on this one input glitch every so often. Appears random and not tied to road conditions. At higher speeds problem is worse. At for example, 45 MPH I may see dips of 5-6 MPH on this input. It never reads higher, always lower.

I pulled the two rear sensors and using a 1K ohm resistor and a power supply looked across the sensors with a scope. Both seem to switch between half the supply and the supply voltage. Removing the sensors will cause a different error so it must detect shorts, opens and in-range.

The toothed ring appears fine. Put car on lift and rotated wheel, no warps or chips. No build up on the sensors. Gaps are about the same, but when I tested the two sensors on the bench, they appear very robust as far as the range of gap they will work at. Sensors are made by Bosch.

Inspected harness from the sensor for about 6' and it all appears good. No signs of anything rubbing on it anywhere. Looked at the harness under hood area, all appears fine.

Replacing the sensor with a new one had no effect other than make my wallet thinner.

The speedometer and cruse control work fine. No other problems I see with it.

It would seem like a break in the harness but all the connectors look great and harness itself seems fine. Looking in a Chilton's manual, there is no information on the ABS including the wiring for it.

PO said that it started doing this at random just before they put it into storage last year. They took it to the dealer for the last oil change and asked about the problem. Dealer stated they could not find a problem and to just see if it clears up. Not sure what that means but getting it second hand.

Any ideas on what could be the cause would be great. I am to the point I think I will have to take it in to a Ford dealer.

 

[Gus Gorilla]

I'm not sure where your tech level is here but since your using the o-scope a little it can't be bad. No offense intended with this if it's too simple, but I'll start at the beginning.
The speed sensors for this vehicle are active. Meaning they are given 12V on one wire and signal return on the other. Passive sensors make voltage, active sensors use voltage. These active sensors pass the tone wheel teeth the same as all sensors but when it passes a tooth then a gap it creates a different Amperage signal. They will alternate very quickly between 7mA and 14mA. To check the sensor you need to hook up the 12V available at the harness side connector, and a meter in series to measure Amperage, (use some jumper wires). Then rotate the wheel very slowly and you will see the signal change. 7-14-7-14 etc. Make sure your measuring mili-amps, mA. If you rotate the wheel too fast your meter will just average out the reading.
You are correct that the range for the airgap on these active sensors is fairly good. Since they work on reluctance, (instead of inductance like passive sensors) the gap isn't as crucial.
For what you have going on I would suspect a wiring problem. The sensors are solid state so they usually either work or don't. What you can do since you have a tool to look at the wheel speed signal is to get the wheel off the ground, have a buddy turn it as fast as he can, and while watching the signal wiggle test the hell out of the harness looking for it to drop out. If you find a point to make it drop out then investigate there. I would NOT put it in gear to turn the wheels while your under there poking around. Very unsafe. If nothing is found then open all the inline connectors between the wheel speed sensor and the ABS module and look for water, corrosion, and check for loose or backed out pins. Sometimes when a connector is put together the male or female half will push back up into the connector and make poor contact.

 

[lecroy]

Good info. Just used the 1K to limit the current and make sure I did not damage the sensor when using the bench supply.

Just to be clear for anyone reading this. If you hook up a current meter between the sensor and a fixed power supply, like the battery, the sensor will become damaged. As Gus wrote, you would need to look at the current inline with the sensor while it is plugged into the car. I have not verified his numbers.

We lifted the car up last night and rolled the wheel by hand and wiggled all the harness we could get to. Nothing. Without any wiring diagrams, I did not want to spend that sort of time tracing it out. Pulled the connectors off the ECM and ABS and saw nothing.

Well, sounds like it's not a common problem. Time to haul it to the professionals at Ford. I'll post their findings.

 

[bojans]

I had a very similar issue about a year ago. Turned out to be a very tiny split in the insulation of one of the wires. The wire wasn't broken but the corrosion was causing the issue. Real PIA to find.

 

[lecroy]

I had a very similar issue about a year ago. Turned out to be a very tiny split in the insulation of one of the wires. The wire wasn't broken but the corrosion was causing the issue. Real PIA to find.

This is what I suspect. When I looked at the harness I was expecting it to be wrapped and routed in convoluted tube. What I see is a half backed job at best of a wrap job. Much of the harness is out in the open, unprotected. The wrap looks like it was added only to hold the separate wires in place. Strange as this thing must have 20lbs or more of copper in it. With all these sensors you would think that they would do everything possible to protect the harness.

That said, I was looking everywhere I could see to find a rub spot.

 

[bill32399]

I am gonna try to find it but I could have sworn there was some kinda recall or TSB on this somewhere.

 

[lecroy]

I took one more look for fun. Dealer stated that the car was beyond the 3 year factory warranty so I really have nothing to loose looking at it other than my time.


I made a long extension cable to go from the WSS to inside the car using some twisted pair. It appears that the black wire really is a battery ground. Measuring from this to the aux. 12V plug under the arm rest ground side, I get about 50mV. This seems very constant when driving the car.

Looking at the white wire, they control this one. Removing the sensor and substitute with a resistor, 4.5mA does not trip the error, but 4.4mA does. Once the current is in-range, it will clear the error in about 30 seconds, the first time the error happens. Going the other direction, 19.4mA is clear but 21.3mA will trip it. So, I will buy the 7, 14mA as being the normal switch points.

Next I discovered that having an in range current but no speed signal will cause the ABS to apply the breaks even at 5MPH. So I disabled the ABS, then measured the current while I drove the car with a fixed in-range resistance. It never spikes and appears very clean. I ran the current to a higher number to try and force it to glitch while I drive but nothing.

If its in the harness, I would expect that something would have shown up with this.


Removed my extender cable and reinstalled the sensor then took it back out for another ride. Keeping the speed below 35 MPH seems to prevent the error. As soon as the speed goes above 38 - 40, it will trip. Driving below 35 MPH for about 30 seconds on the first trip will clear it.


It really does appear that the speed signal is not stable for this one sensor. Looking at the ring gears again they appear to be a press fit. There is a split in the gear for it to open up. The sensor's air gap and centering appears the same for both back sensors. However, width of the split on the sensor that is acting up is much wider than the other one. So the distance between the two teeth the overlap the split in the gear is about 0.015" wider.

What the scan tool reports is what the software wants the scan tool to report. I would guess they have a software filter for the all of the WSS and wonder if the filters cutoff changes with the wheel speed. So for a higher speed they go to a higher cutoff and that's why I see the dip at higher speeds and not at lower ones.

Not being the original owner, I wonder now if the cars ABS had ever been reprogrammed and they have a tighter requirement now for the ring rears teeth spacing than when the car was first sold.


..........................................................

Looking at the ring gear, that thing can be moved just using my fingers. I moved the gear to the inside about 0.1" then out about 0.1". The trip speed was the same for both cases. I knew from my first tests that the sensor seemed pretty robust for the air gap but as easy is the gear is to move, I wondered if it had slid. Maybe the gap opens enough as the speed increases to cause the problem. Doubtful but not ruling anything out at this time.

 

[lecroy]

Dang, its a common problem with the Ford. Found it after I knew what to look for.

http://www.explorerforum.com/forums//showthread.php?t=251345

http://www.aboutautomobile.com/Complaint/2006/Ford/Explorer/Electronic+Stability+Control+(ESC)

I thought that split was supposed to be there. Another design problem. I'll get the new ones next week and change them both out. The one split must just not be bad enough but hate to just do the one side.

 

[lecroy]

Changed both rings out tonight. Pretty quick job. Left the axles in. Just removed the sensor, caliper and the 3 bolts. Maybe an hour for both sides. Solved the problem.

Once the first ring was off, I had it in my hand and I broke it. I was not putting the iron grip to it. I got to looking at the ring has several cracks in it. There was a hair line that was holding the ring together. I looked at the second ring, same. I am surprised the rings had stayed together.

New rings are about 50% thinker, not double.

 

[Bill MacLeod]

Wow, great diagnostic work on your part.

Would you mind posting the ring(s) part # for others future reference?

 

[rgoltsch]

Changed both rings out tonight. Pretty quick job. Left the axles in. Just removed the sensor, caliper and the 3 bolts. Maybe an hour for both sides. Solved the problem.

Once the first ring was off, I had it in my hand and I broke it. I was not putting the iron grip to it. I got to looking at the ring has several cracks in it. There was a hair line that was holding the ring together. I looked at the second ring, same. I am surprised the rings had stayed together.

New rings are about 50% thinker, not double.

I know this is an older thread, but I thought I would add one thing to this post. If you have this issue with one wheel, you might consider replacing both when it crops up. My wife's 06 Explorer had this issue late in 2011, we replaced the passenger side ring and all was good.....until about 9 months later, the driver's side started with the same error. We had to replace that one this week.

The part was only $26 from our local Ford dealer, I don't have the part number, but it is called the Tone Ring. And yes, the new Tone Ring looks a lot beefier than the one it replaces.

 

[Happster]

Same problem here with a 06 Exploder. ABS and Traction Control light would come on after we reached 10mph and would stay on until we shut her down. Tone ring was split. Replaced it (part # 7L2Z-2C182-A for the guy that asked) and now the same lights come on and turn off sporadically. Pretty sure the tone ring is true. I had installed a speed sensor on the broken ring before I knew it was broken, so I want to check the air gap clearance. The broken ring was obviously expanded. Anyone know the spec for the gap? Any other thoughts on what might be causing erratic sensor operation?

 

[rgoltsch]

For what it is worth, we replaced one, then had to replace the other one a few months later. Do a code scan and see if it is still the same wheel.

 

[mcycleboy]

I have had ABS problems on two different 4th generation Explorers. My first Explorer I kept for over 200k miles and had replaced the front hubs several times during its life which when worn cause ABS problems often. Other things to look for that throw odd codes is bad connections from the sensor plugs to the wiring harness. I found moisture in a rear left connection that would cause very intermittent ABS problems that followed me for a long time before I took them all apart and inspected them. On my newer 4th gen Explorer I found, unbelievably, a similar intermittent problem that drove me crazy. I finally noticed a large connector #C134 behind the right wheel well - under the truck that was causing the intermittent problems. I have not seen these tips posted so I thought I would post my findings here. I never had a rear tone ring go bad...yet but of course those can be hard to see at times. Also I have heard that a C1278 code - steering angle sensor - is often not accurate. The steering angle sensor does not fail as much as people think in my opinion. So...first suspects are front hubs...then tone rings for the rear...then check all the wheel sensor connections including C134. One more thing...rodent wire damage in the right engine wheel well area...check carefully and under the air cleaner for damage. All the above are not hard fixes you can do before you succumb to taking it to a dealer . I changed my own hubs out with good quality branded hubs (non chinese) without much problem. The first one took me over 2 hours but after than it was about 45 min per hub. Lots of youtube postings on how to do this yourself if you are good with a wrench.