ABS (Wheel Speed Sensor) Waveforms and Testing - Drive Accord Honda Forums | radio-pro.ru
  • 2 Post By JohnNH
LinkBack Thread Tools Search this Thread Rate Thread Display Modes
post #1 of 4 Old 01-26-2017, 04:53 PM Thread Starter
3rd Gear

Join Date: Nov 2013
location: New Hampshire
Posts: 153
Thanks: 2
Thanked 144 Times in 56 Posts
ABS (Wheel Speed Sensor) Waveforms and Testing

Given that there are many different kinds of ABS sensors (2 wire passive, 3 wire active, 2 wire active) in use on different vehicles, I thought it would be interesting to figure out what type the 7th gen Accords use and what the expected output signal is.

The front ABS sensors can be accessed at their connectors under the hood:

On the sensor side, for the front sensors, the pink wire is the supply wire and the white wire is the output signal/ground wire (Wiring Diagram thanks to BBB Industries):

Backprobing the Pink wire should show a constant 11V with the key on. Notice that this not the battery voltage and appears to be a regulated voltage rail generated in the PCM:

The white wire is the combined sensor “ground” and output signal. Backprobing the white sensor wire shows the following square wave signal as the wheel is spun by hand. The lower level is approximately 0.7V and the upper level is approximately 1.4V. The frequency of the square wave is proportional to the speed at which the wheel is spun:

Here is a zoomed out view showing how the signal changes with wheel speed:

Notice that each time the wheel is spun it ends up remaining in a random state (either high at 1.4V or low at 0.7V) depending on which pole of the bearing ring magnet the wheel came to rest at. As a result, a simple ABS sensor test can be performed using only a DMM (voltmeter) if no scope is available, by simply measuring the sensor return voltage after spinning the wheel several times. Sometimes you should see 1.4V when the wheel comes to rest, and other times you should see approximately 0.7V. If you ever see 0V there is probably a wiring problem (open circuit) or sensor failure.

To test the ABS sensor output with a DMM (Voltmeter) only, connect the negative (COM) terminal of the voltmeter to chassis ground and connect the positive terminal (V) to the WHITE ABS sensor wire by backprobing at the connector. Then, spin the wheel several times. Sometimes the output should settle at approximately 1.4V and other times it should stop at approximately 0.7V. (This is not a complete test, as there still could be a problem on a particular portion of the ring magnet, or a dynamic problem, but at least it does provide a basic functionality check of the sensor, verifying that it is detecting both poles of the ring magnet and that there is no problem in the wiring harness).

There are several types of ABS sensors that have been used on different vehicles including 2 wire passive sensors (older), 3 wire active sensors and 2 wire active sensors. Active sensors are used on most newer vehicles due to their ability to sense down to very low wheel speeds. The wide variety of sensor types can lead to quite a bit of confusion as to how to test the different ABS sensors and what type of signal to expect. On this 2007 Accord, the ABS sensor is a 2 wire active sensor. The 2 wires serve two different purposes at the same time: (1) they provide the voltage to power the circuitry in the ABS sensor and (2) they simultaneously provide a path for sending back the return signal indicating wheel speed. This is accomplished as shown in the following diagram:

As the alternating North and South poles of the ring magnet (integrated into the wheel bearing) pass by the Hall Sensor (a semiconductor magnetic field sensor), the electronic circuit in the ABS sensor opens and closes a switch inside the ABS sensor which changes the overall resistance through the sensor. This results in two different levels of current (red arrow) returned to the PCM, a higher current when the switch is open due to being over one magnetic pole and a lower current when the switch closes when the sensor is over the other magnetic pole. These two current levels are reflected as two different voltages (0.7V or 1.4V) as determined by the resistance inside the PCM relative to the two resistance values in the ABS sensor. These two signal voltage levels are designed to both be relatively low to ensure that in either state, the voltage across the ABS sensor is maintained at a high enough level to power its internal circuitry. The benefits of an active sensor are that it can sense at very low wheel speeds and it is more immune to electrical interference (since they output a digital signal rather than an analog sinusoidal signal). The advantages of the two wire active sensor over the three wire active sensor are twofold: (1) one fewer wire is needed to the ABS sensor and (2) since there is a current flowing in both ABS sensor states, there is continuous feedback regarding the health of the ABS sensor and the state of the connection. In comparison, in a three wire sensor an open-circuit or short on the signal wire might not be immediately differentiable from the sensor just being in a low state. In the 2 wire sensor, if there is ever zero current (or current higher than the expected level in the closed switch state ) then the PCM knows immediately that there is a problem with either the ABS sensor or the wiring to it.

visionguru and salcuta like this.
JohnNH is offline
The Following 3 Users Say Thank You to JohnNH For This Useful Post:
jfuredy (01-27-2017), mtts60 (01-26-2017), rookie (01-26-2017)

post #2 of 4 Old 01-26-2017, 07:54 PM
5th Gear

Join Date: May 2005
location: DFW
Posts: 821
Thanks: 25
Thanked 68 Times in 56 Posts
I don't understand all you said but I'm getting some stuff. Thank you, will study this a bit more.

One question: why would they use regulated 11V for this? Is it to give some sort of safety margin so the voltage stays constant in case alternator / battery have issues (and voltage drops) so the system still operates while the car runs?

Are there other systems in the car that use lower voltage like this? I did not actually consider this.

2017 Accord EX I4 w. Sensing Sedan
2005 Accord LX I4 Sedan > the one with a $2500 transmission rebuild
rookie is online now
post #3 of 4 Old 01-26-2017, 08:12 PM
DIY Kid/Hypermiler

Das Chicken's Avatar

Join Date: Sep 2014
location: Georgia
Posts: 584
Thanks: 59
Thanked 97 Times in 69 Posts
The last diagram showing that there are multiple magnets in the wheel bearing assembly explains alot. I always wondered how speedometers registered accurately at low speeds. I thought they only had one magnet.

I feel like you would get a kick out of autospeed.com, many of the articles there analyze car electronic systems and components.

Originally Posted by rookie View Post
Are there other systems in the car that use lower voltage like this? I did not actually consider this.
The ECU gives 5V to many engine parameter sensors like the intake air temperature sensor, etc.

To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.

Originally Posted by qman View Post
Ah so you do have a drinking problem. You do not drink enough.
Originally Posted by RickBlaine View Post
When I was little girl in Russia...

Originally Posted by Cropgun View Post
You high?
2006 Honda Accord EX 6-6 Sedan Tafetta White 152K miles. DIY coroplast undertray, hybrid rear diffuser, Odyssey intake spacer milled down to 1.3", Engine block heater, Power steering delete, Acura RSX rims
Das Chicken is online now

post #4 of 4 Old 01-27-2017, 03:58 AM Thread Starter
3rd Gear

Join Date: Nov 2013
location: New Hampshire
Posts: 153
Thanks: 2
Thanked 144 Times in 56 Posts
Originally Posted by rookie View Post
One question: why would they use regulated 11V for this?
I don't know for sure, but at least one benefit is that this stabilizes the voltage of the upper and lower logic states (the 0.7V and 1.4V levels). In this particular setup, the two voltage levels are created by a voltage divider (so input voltage, 11V, is simply scaled down by the resistors). Therefore, the 0.7V and 1.4V levels will vary proportional to the input voltage (the 11V). If they didn't use a regulated 11V and instead used the battery voltage directly, this can vary from something like 11V to 14.5V or so which is about a 30% variation. That means that there could be a 30% variation in the 0.7V and 1.4V levels as well (so the 1.4V level might be as high as 1.8V or so and the 0.7V might be as high as 0.9V). The variation in these levels could make it harder on the PCM to reliably detect between the two threshold and lead to less "noise margin".

Originally Posted by Das Chicken View Post
I feel like you would get a kick out of autospeed.com, many of the articles there analyze car electronic systems and components.
Looks interesting! Thanks for the tip, I'll check that out!
JohnNH is offline


2 wire, abs, active sensor, wheel speed sensor, wss

Quick Reply

Register Now

In order to be able to post messages on the Drive Accord Honda Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
The answer to the random question may be found under the Off Topic section of the forums and in the "Drive Accord Forums" category.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid email address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Thread Tools Search this Thread
Show Printable Version Show Printable Version
Email this Page Email this Page
Search this Thread:

Advanced Search
Display Modes Rate This Thread
Linear Mode Linear Mode
Rate This Thread:

Posting Rules
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to

Related pages

honda nardy2008 honda accord vsa light2005 honda accord aux input locationfuel economy chipsplasti dip shift knobhonda civic lx seat coverspolk audio 6x9 speakerswhat is the purpose of a valet keywhat is the normal transmission temperaturecarbon fiber hondapainting intake manifold1993 honda accord problemszentec hidhonda car racing gamesoil minder2003 honda accord windshield wiper motorstagg shocks reviewhow much coolant flushbrake fluid flush diyhonda civic oil pump2006 honda accord recallrear brake leaking fluid1996 honda accord exhaustbattery for honda civic key99 honda civic radio codehonda odyssey windshield replacementis250 vs g37radiator fan not turning on2007 honda civic rear control armcode p0420 honda accordk n air filters best pricehow to turn off srs light on honda accordhir2 bulboem stereo replacement2004 honda accord coupe specsphotochopped92 honda accordengine oil in radiatorhonda accord headlightrod knock symptoms2004 honda crv towing capacityhonda pilot fog lightshonda civic trunk matcostco tires bridgestone992 bulbwww vtec netpure one oil filterhonda blind spot information system2008 honda accord timing chainhonda tpms reset toolhonda sirisupercharger honda accordcivic stereo codeintermittent wiper control modulesafelite glass repair costacura care94 accord camber kithonda accord drawingpioneer avhx3500bhsvvscv1honda accord 2004 fuel economy2001 honda accord towing capacityvarrstoen es42014 honda crv remote startsrs light on hondaphilips 921 ledmotorcraft sae 5w 20 super premium motor oilhonda distributor coilportable tire balancerhonda accord timelinehow much does it cost to repaint a bumperalternator whining noisewhat is dexos approvedcostco autobuying