Yellow 2 speed sensor was not showings speed.. was getting almost no mv ac when spinning the wheel.. with sesor push all the way in. Cleaned tone ring with brake cleaner fluid and retested. Got plenty of mv ac. Plunged sensor back in and spund the wheel, abs light turned off.. great video.
I wouldn't worry about the ohms so much. It's a quick test to ensure the sensor has nothing open or shorted. If you have none of those then spin the wheel and check a/c volts
Use an oscilloscope, it's much quicker, you can actually see the waveform produced by the voltage produced at the sensor and you can also tell if the exciter ring has warped.
I own Skoda Yeti , which has been very sparing used and we'll maintained , for sometime ABS is continuously glowing . The authorised work shop advised for it's replacement but as the car has run only 14K kms am not convinced with their advice. Therefore looking some Work shop in Delhi NCR where the problem can be fixed economically & effectively . Advices r solicited. Thanks.
Estoy mirando estos tutoriales ya que en un Toyota Corolla 2011 s, se encendió en el panel de instrumentos el fallo de la figura del carrito estababilidad , checaré Sensores Abc y niveles de líquido de frenos.... Gracias
Ok, so I tested my wheel speed sensor and it’s brand new just bought it front autozone and it’s not reading correctly and I’m trying to do the volt test while spinning the tire and I’m getting very low reading.
hi I drive a 4x4 Dmax, my ABS lights kept turning ON only after 15Km to 25Km of driving... when I stopped the car for 20 to 30mins then restart again...the ABS light is off until I drive another 15km to 25km I went to 2 Isuzu workshop...and their diagnostic cannot show or tell the reasons why it ABS lit up. Can anyone hv same experience?
Is that really a hall sensor? In a service guide issued by another supllier, i have learned that you could damage the hall type abs just by measuring its resistance. and, i do not thing that hall sensor generates voltage, it works more like a switch which closes the circuit, but the voltage must be applied to it.
You are correct. The video shows how to test an older type "permanent magnet" wheel speed sensor, which produce an AC voltage signal as the wheel rotates. However, many newer vehicles use an electronic sensor instead. The most popular ones I've seen use two wires and are called "magneto-resistive" sensors. They use a current loop output to send the wheel speed signal to the ABS module instead of an AC voltage signal. The ABS module applies 12 volts to the plus terminal of the sensor. Then the sensor minus lead goes to one end of a shunt resistor located inside the ABS module. The other end of the shunt resistor is grounded inside the ABS module. This sets up the current loop though the sensor and the ABS module. Current flows from ground, through the shunt resistor inside the module, through the sensor and to the +12 volt supply. As the tone ring rotates the sensor's electronics change the conduction resistance of the sensor. As such the voltage across the shunt resistor inside the ABS module will alternate between about .8 volts and 1.20 volts creating a square wave to form as the wheel rotates. The frequency of the square wave increases the faster the wheel turns. The rest of the module's electronics then use the square wave to determine wheel speed. To my knowledge you can't harm a magneto-resistive sensor by hooking it up to an ohmmeter. However, you can't test it that way either because it needs to be powered up and connected to a shunt resistor to work. The way I test them is to provide my own external current loop, which is very easy. First, unplug the sensor from the car and check the wires coming out to the sensor from the ABS module and verify that you have +12 on the plus lead. Then check the resistance from the minus lead back into the ABS module. It should typically be around 110 ohm. This tells you the wiring going from the wheel well to the ABS module is good both ways and that the shunt resistor inside the ABS module is good and that the module is sending +12 to that wheel. It also tells you what the resistance value of the shunt is. Once you know the value of the resistance get a resistor (typically around 110 ohms or so) and connect one end of the resistor to the minus terminal of the sensor. Then ground the other end of the resistor to either the ground of the battery or an external power supply if that's more convenient. Then apply +12 volts coming from the battery or an external power supply to the plus terminal of the sensor. This will set up your external test current loop. Put a voltmeter across your external shunt resistor and you should read either .8 volts and 1.20 volts. Then as the wheel is rotated by hand a good sensor should start pulsing the current up and down and the voltage should start switching across the shunt resistor. Then when turning the wheel even faster it will create a square wave as the wheel rotates at a higher speeds and the frequency of the square wave will increase the faster the wheel turns. If you put an oscilloscope across your shunt resistor you will be able to look at the square wave. This method helps you get around the fact that magneto-resistive sensors have to be powered up and in a circuit to work while being unplugged from the vehicle's wiring harness so you can access the connections. Once you verify that the wiring going to the ABS module and the module itself is good and then that the sensor is also good you can be pretty sure that when you plug the confirmed good sensor back into the wiring harness the signal will be getting into the module from that wheel.
@@joevignolor4u949 Thank you for such an extensive explanation! Wery informative! I am just starting to learn things about how sensors work and how to diagnose and this could be my lesson II :-) (the Lesson I was given by Bosch instruction booklet)
@@jandanko974 Let me give you some additional tips. Let's make sure you don't get burned the same way I recently did. I'm not a professional mechanic ether but I think that based on what I've seen a lot of them don't really understand exactly what's going on with these ABS systems either. I have extensive experience as an industrial engineer with sensoring of this type. It's been used in industrial speed sensing equipment well before it migrated into automotive applications. I recently had to work on a friend's vehicle with an ABS problem. I had some problems initially until I did the necessary research and figured out that it didn't have the old style permanent magnet type sensors and had the magneto-restive type instead. It was a wild ride and I wasted a lot of time and effort and when I read your post I didn't want you going down the same path that I did. Part of the problem involved some sort of design defect in the software algorithms in the ABS module that caused it to throw the wrong fault codes. It threw codes that told me all four ABS sensors were bad at once. This is impossible of course so it pointed to something more centralized. Thinking that I went onto the wiring first and finding nothing wrong there I changed the ABS module. But that didn't fix it ether. Unfortunately I didn't have access to an expensive professional grade scanner. If I did I could have taken the car for a test run and looked at the speed signals coming form all four wheels and that would have pointed me back to the wheel speed sensors, which is where I would have gone first if not for the bum steer I got from the trouble codes. Once I decided that the trouble codes were wrong because I had eliminated everything else the only thing left was the four wheel sensors. Next I figured out how to functionally test the sensors as I described it to you. I then quickly determined that it was just one bad sensor in the front all along. After changing the bad sensor the f...king ABS light finally went out. Unless you have access to a professional grade scanner to look at the individual wheel speeds my advice is that given the fact that most ABS problems are caused by the sensors or the associated wiring that you check the fuses first to eliminate them and then check the sensors first before going deep into the wiring or replacing the ABS module. If you do get a single ABS code for one just wheel check that one first. Otherwise check each sensor one by one starting with the front ones. I can tell you from my recent experience that changing out a perfectly good ABS module is not something you want to do. To prevent doing what I did perform a proper functional test of all the wheel sensors first. Odds are that's where the problem is.
@@joevignolor4u949 Hi this is great advice you are giving. There are a lot of videos on You Tube for the passive sensor and people don't realise this. I too thought i could put a multimeter on the wheel sensor on ac voltage and turn the wheel but that only works on passive. What i did notice though is on resistance setting the left front sensor changed numbers but the right front sensor didn't move, could this be a sign one isn't working.
