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This vehicle throws a code for left front speed sensor. I have done everything to this vehicle. Sensors, hub bearing, abs computer, swapped sensors side to side, etc.. When monitoring the datastream, sensor reads good all the time. I even used my volt meter to test the signal directly out of the sensor and going into the abs module--no glitches or drop outs (thats why I replaced the module). I have ensured all connections are clean and making good contact.

I can clear the code and watch the datastream, monitoring the left front wheel speed and it matches all the other wheels but before I get out of the parking lot, the code is thrown and the abs and trac light come on.

Any ideas?

What I would do is use a dual trace labscope. Backprobe both front wheel speed sensor at the ABS module and road test. I need to know that the waveforms are exactly the same. It's important to proble at the module to know that the wiring is good. Any history of accidents/crashes with this vehicle.

I have done continuity test on the wiring. Unfortunatly I do not have a dual trace lab scope. The fact that the datastream shows the wheel speed with no drop outs should be and indication the wiring is good and the sensor is producing a good signal AND that the module reads it. Also, as I mentioned previously, the speed matches the other wheels, but the module still thinks the wheel is skiding. The ABS engages!!

Here is something I forgot to mention previously. Early on with this problem, I swapped the front sensors and the problem went away for about a month. When the vehicle came back, I rechecked all wiring and connections again.

I checked identifix, several harness repalcements. If you have a Fluke 88 meter you can set it to low ohms high resolution and reteet harness. May show something that way. HTH, Jeff.

Ummmmm....... Does this vehicle have a new tire or 2? or is spare on?

Princeton Auto wrote:I have done continuity test on the wiring. Unfortunatly I do not have a dual trace lab scope. The fact that the datastream shows the wheel speed with no drop outs should be and indication the wiring is good and the sensor is producing a good signal AND that the module reads it. Also, as I mentioned previously, the speed matches the other wheels, but the module still thinks the wheel is skiding. The ABS engages!!

Here is something I forgot to mention previously. Early on with this problem, I swapped the front sensors and the problem went away for about a month. When the vehicle came back, I rechecked all wiring and connections again.

The problem is the scan tool you are using to read the speed is probably not fast enough to capture the issue. That's where the scope comes in. It's much quicker sampling rate will probably catch this. It's obviously seeing something erratic and activating. You may be able to capture the harness problem that way too. Know anybody with a scope?

Sub harnesses are a real problem on these.

Thanks for all of your input. I did borrow a Snap-on Vantage Pro when I was checking the sensor and input to the module and that did not show any signal interuptions.

Also, on the scanner, I did reset that screen to show just the front two sensors, graphing, and that did speed up the monitoring. When the abs engaged, I could monitor the sensor and it was still reading a speed. This is at slow speed. The code sets with slow speed maneuvering, parking lot type driving, not city street driving conditions. If you clear codes and head out on the street the code will not set--again, only slow speed stuff, 0-8 miles per hour.

Keep it coming. We will get this fixed.

Just a note on the Vantage.... it's a graphing multimeter, not really a scope. It may not capture the glitch either.

Sometimes the amplitude of the signal is low due to excessive clearance issues.....no problems like that?

Fortknoxx has a good point. Check to make sure the tires on this vehicle are all the same size AND they are all worn about evenly (ie, a brand new tire on one front wheel and a worn on the left) Different tire sizes can throw the ABS computer for a loop and can get past even your experienced technicians.

a couple of real quickies here. was the mount where the sensor sits cleaned well. i've had a few where the mount was a bit dirty and this made the sensor sit just a bit out of whack. i hope all was oem including bearing. i can count on my fingers and all those who attended the last super bowl how many times after market parts have led me on a wild goose chase. my rule of thumb on any gm suv abs trigger issue under 5mph is a replacement of both hubs and sensors in the front with oem or at least top line assemblies. all parts stores offer two lines. never, never, never, use or give the customer an option to. i learned the hard way and i learned very, very hard.

I HAVE THE SAME ISSUE ON AN 05 EQUINOX AND I HAVE REPLACED EVERYTHING WITH OEM DEALER PARTS. JUST WONDERING IF THERE WAS A FIX.

WHATS THE POINT OF HAVING A FORUM TO HELP OUT EACH OTHER IF WE DONT POST THE REPAIRS?

ricmorin wrote:Just a note on the Vantage.... it's a graphing multimeter, not really a scope. It may not capture the glitch either.

He mentioned it was a Vantage Pro. I thought the Pro was a lab scope just like the Modis only it's 2 channel?

FRONTLINE wrote:WHATS THE POINT OF HAVING A FORUM TO HELP OUT EACH OTHER IF WE DONT POST THE REPAIRS?

happens on occasion. don't let it hammer away at you, sometimes the fix isn't posted because the poster is a hit and miss. for the most part you'll get your answers.

i took a few minutes and read the description aspect of the system. man, talk about a barrel of monkeys. if your vehicle is throwing a sensor code i would take it on a test ride with another person/tech and while they're driving watch the wheel speed monitors. especially under 5 mph. if the light comes on at higher speeds i would watch the sensor readings on slowing down while coming to off ramps on the interstate. tina made a huge hit with the tire post. at high speeds this will cause an issue. i'm starting to feel that this may be a 4 tire replacement at a time vehicle. there are more than a few systems tied into the sensor readings. i've run into situations where a tech 2 is needed because of the sensitivity level. i've seen issues where 4 tires were replaced with a "close enough" version. check specifications for tire size. i use tire rack. were rims replaced?

sbebenelli wrote:

ricmorin wrote:Just a note on the Vantage.... it's a graphing multimeter, not really a scope. It may not capture the glitch either.

He mentioned it was a Vantage Pro. I thought the Pro was a lab scope just like the Modis only it's 2 channel?

Check the sampling rates and compare. Can't say for sure on the Pro version. I own an older one that I use occasionally, but not very often. A true lab scope has a much higher sampling rate. Still, the Vantage is useful in many applications.

MY O5 EQUINOX HAS ALL FOR NEW TIRES AND THE PROBLEM STILL EXIST. THE ONLY THING I HATE MORE THAN NOT FINDING THE PROPBLEM IS WE SOLD THE CAR TO MY GRANDMA. LOL. SO ITS NEVER GOING TO LEAVE ME.

JUST TO THROW THIS OUT THERE TO. I USED A SNAP-ON VERUS AND ALL THE WHEEL SPEED SENSORS ARE SHOWING DOUBLE WHAT THE SPEEDOMETER SHOWS.

ricmorin wrote:

sbebenelli wrote:

ricmorin wrote:Just a note on the Vantage.... it's a graphing multimeter, not really a scope. It may not capture the glitch either.

He mentioned it was a Vantage Pro. I thought the Pro was a lab scope just like the Modis only it's 2 channel?

Check the sampling rates and compare. Can't say for sure on the Pro version. I own an older one that I use occasionally, but not very often. A true lab scope has a much higher sampling rate. Still, the Vantage is useful in many applications.

i have a older lab scope sitting in the corner of the shop. i have the ability to down load the "movie" into it and read the graphics. sometimes i feel i need the screen from the new Dallas Cowboy's stadium to see a glitch.

FRONTLINE wrote:JUST TO THROW THIS OUT THERE TO. I USED A SNAP-ON VERUS AND ALL THE WHEEL SPEED SENSORS ARE SHOWING DOUBLE WHAT THE SPEEDOMETER SHOWS.

dbbl or just higher? are you reading kph vs mph? i've made a few visual boo boo's like this before.