How To Test Abs Module With Multimeter

j-bone

I'thousand testing a suspected bad abs module , the abs is kick on at low speeds for no reason and information technology is killing engine power at low speeds as well .
Data logged the ABS module yesterday and found some interesting data.
so in park with engine running all 4 wheel sensors read 2mph
after driving around finally got the abs turning on on data log , front end 2 wheels sensors drop to 2 mph rears nevertheless read iii and its dumping left front end cycle valve .
there was a stored just not active lawmaking for steering angle sensor likewise .
is this enough info to consider the module bad ? are there any other tests to perform ?
i can send a copy of the data log if anyone would like to check information technology out as well.

mrrsm · Apr 28, 2019

The ABS Wheel Sensors utilise Stock-still, Fine Wire Induction Coils that generate an Alternating Current vs. the movement of the 'Fine Teeth' of the Reluctor Rings mounted to the rotating portion of the Wheel Hubs. If the Torso of the SUV was vibrating plenty to shuttle dorsum and forth while the vehicle was in Park... (...think... Bad Motor Mounts here...) THAT might be just plenty motion for it to motility the Tip of the Fine Wire Consecration Coil back and forth vs. a Unmarried Molar of the Reluctor Band inside of the Wheel Hubs and trigger a reaction from the PCM by inducing simply enough AC flow to create the Simulated MPH reading. If the Wheel Hub Bearings are badly worn and permit for this "play"...that might play another function in allowing your parked vehicle to behave like a Admirer Tourist... ambling slowly along on foot past the Savoy Theater in London, England. :>)

The problems normally encountered with the ABS come in two parts:

(1) The individual ABS Fine Wire Induction Coil Sensors can get "pushed away" from the Reluctor Rings inside the Bike Hubs due to the fact that when Oxygen and Iron and Steel combine to form FE2O3 (Ferrous Oxide) the MASS of the ii expands as blobs of Rusty Metal ...and that expansion causes the ABS Sensors to Malfunction as the Tip of the Fine Wire Induction Curl in the Wheels become moved further abroad from the Teeth of the Reluctor Rings. The Set up for the problem is well illustrated in this Brilliant Video:

(ii) The Modern ABS Organisation is non just an Electronic Organization... it is married well and truly to the reality of Hydraulic Brake Fluid moving through the Brake Lines and is just as dependent upon having No Air or Water within of the Brake Lines and Restriction Cylinders. Take a look at the quaternary Video down inside of Post #9 at this Thread. You lot will need a "GYMKO" Tech ii or a similarly capable Bi-Directional High End Scanner to perform the actions herein described involving a Dealership Quality Brake Bleed and ABS Purge:

Boosted Tech 2 & VXDIAG Nano Resources

EDIT: On Nov 11th, 2019, :I created a TOC (Tabular array of Contents) of the Video Files shown consecutively in the following Threads that should assistance to speed the identification of Specific On Topic Videos vs. having to Read and Scout each one in sequence to locate what the Viewers demand. The...

gmtnation.com

j-bone

I fully understand how the abs system operates and the data it needs to operate.
While I'thousand Not doubting you on the sensors pushing away from the selection up ring I find it very hard to believe all 4 sensors have the same problem and an hour of driving every time I stop all 4 are still at 2 mph even with engine off it even so reads the same .
And yes I am using a tech ii .
I volition practise the ohm and voltage test as I have to change pads and rotors this week .
Along with all the other problems I'chiliad chasing information technology doesn't seem like 1 sensor would cause so much havoc only I've been wrong before

mrrsm · Apr 28, 2019

If the ABS demanded that "all four wheels" must sense the aforementioned slipppage simultaneously... say when having "Black Ice" on only one side of the roadway... they would never work ...and the purpose of having an ABS would be defeated. It should merely require having I Wheel sending data that information technology has ceased to rotate to trigger the proper arrangement-broad ABS response.

Please empathise @j-bone ... that whenever I provide data in Whatever posts... it is with the thought that I tin can never guess what a person knows... or does not know... most the bug they are asking to get help on. Ergo... I try to include every bit much information every bit possible because more than one person will visit your posts and many other similar posts, looking for additional, complete and useful information based upon your experiences...and the assistance rendered by the many contributing GMTN Members.

Your cognition, acumen and skill set about Mechanics cannot exist determined from what y'all wrote in Post #1. And so my replies are meant to be as comprehensive equally possible and never written equally a challenge towards your mechanical understanding. They are always free of any malice or debasing intent in heed. Y'all will determine in time whether or not any of these ideas are worth investigating by the success or failures of your repairs.

"When the Educatee is Ready... The Teacher Emerges..." Confucius

j-bone

Yeah sad I didn't mean to audio arogent , I understand you lot can't know the skill set on the other end of the forum .
I take everything with a gain of salt no matter the source.

budwich · Apr 28, 2019

As y'all plan, I would practise some resistance measurements towards the sensors merely also do some voltage measurements (or resistance measurements with power asunder) towards the module inputs to run across if anything is out of identify. It is unlikely to be sensor issues. My estimate would be either ABS module OR battery / footing conditions at the module as it is unlikely that all sensors have the aforementioned "mistake".

I guess 1 other question would exist... when was the concluding time you checked your brakes (calipers)? frozen calipers could be a problem with brake pressures.
The before comment about "killing engine power at deadening speeds" is somewhat puzzling both in terms of what does that mean (ie. how did you lot determine this) and how is this an ABS system function... ie. kill engine power.

Forget the "impale engine question"... I see abs (EBCM) has a function to request the PCM to reduce engine torque. :smile:

sorry one other question: what is your pcm indicating is your vehicle speed while in park?

j-bone

starting time off i never said what vehicle this is :bonk: , 2006 buck ranier AWD V8

Ok so some updates and more information on the whole scope of problems i'm chasing and why I recall its something more than and then a sensor.
offset an update on the sensors , curiosity go the all-time of me and decided to probe the forepart two sensors and practise the brakes.
the sensors had a piffling over 1k ohm and simply produced 200mv ( this is a alive front end axle so it has high resistance I set the fluke to min max and spun it the best i could ) the hubs did have the stainless shims which are completely useless at preventing rust . cleaned it upwards and got iv-500 mv doing the same spin examination we will come across if information technology helps anything.
front calipers were not seased and slide pins are free.
So the "kill engine power" situation has happened to me once and my mom a bunch of times simply information technology was a very low speeds it kills the traction control ( lite is illuminated for the remainder of the bulldoze ) and simply had idle for a few seconds regardless of pedal position just returns to normal dive-able status.
another bug that i think are related somehow
the air suspension doesn't e'er pump upward (pump is fairly new )
yous tin can drive it on the crash-land stops and it will return to normal when information technology feels like information technology .
at present at that place is no interior lights with door or key ( dash switch turns them on fine )
rear tailgate doesn't go ability sometimes ( wont lock or work the rear wiper)
no nuance data at times ( all gauges part even when the information does not work )
when the data center is working there is a " check stabiltrak" message ofttimes ( checking with my non tech 2 had provided no information )
y'all can see my original thread hither
https://gmtnation.com/forums/threads/06-rainier-no-dash-data-center.19148/#post-577347
maybe they should exist merged at present ...?
I volition cheque pcm mph in park and report back !

mrrsm · April 28, 2019

The LGM (Lift Gate Module) in the Rear Hatch can become shorted in the Power Harness Connector to the LGM due to Electric 'Arcing and Sparking' acquired by excessive Body Vibrations and damage the internal Logic Board. Also, if you pull the Rubber Grommet-Tube containing the wiring leading to and from the LGM to the Wiper Motor... information technology is possible that the 12 VDC Wires AND the 5 Volt Reference Betoken Wiring tin get bent back and along often enough during the normal opening and endmost of the Lift gate to cause the Wiring inside to 'work harden' and separate.

The resulting loose wires can Brusk the LGM either to Ground or to 12 VDC Power and and so play Hell with the Class 2 Network. You can use your Tech 2 to investigate the Lift Gate Module and see if you take whatever bi-directional communications. If not... Well... that would be a good place to get-go sorting out any Class 2 Network shorts that can often impact everything else y'all are having problem with equally a result, Module wise.

This video illustrates the problem. If you find whatsoever such problems... Pull any relevant Fuses to the Lift Gate FIRST before attempting to perform any soldering and Heat Shrink Repairs equally yous do Not want to accidentally put power to that LGM before cross-checking all wires and-or having the repaired connections going "Hot' before the work is completed:

j-bone

Yes I agree that if all wheels read the same but are off to actual vehicle speed the abs system is happy . If other take this non zip condition and abs is working correctly so I'one thousand ok with that .
Upon further reflection on yesterday, the front left hub had more resistance and then the correct , both were not loose, also no grease or other foren objects on the ring or sensor .
Time will tell if the hub is on its style out .
Plan to bidirectional test the body / rear hatch this week .
On a slight tangent , I'm asked if the vehicle has auto or manual hvac when entering data in the tech 2 how would one know which is present ?
There is an " motorcar " button on the hvac console is it that unproblematic ?

16vcabman

I fully understand how the abs organization operates and the information it needs to operate.
While I'yard Not doubting you on the sensors pushing abroad from the selection upward ring I find information technology very hard to believe all iv sensors take the same problem and an hour of driving every time I stop all 4 are still at ii mph fifty-fifty with engine off information technology nevertheless reads the aforementioned .
And yes I am using a tech ii .
I volition exercise the ohm and voltage test as I have to modify pads and rotors this week .
Along with all the other problems I'grand chasing it doesn't seem similar one sensor would cause so much havoc but I've been wrong earlier

Actually It can and there is a TBS on abs coming on at slow speeds. Pull the sensors cake the pigsty, take of rust, spray with cold galvanizing paint lightly. Yous exist amazed. Front hubs are the well-nigh sensitive part of the sensors doing exactly what your describing.