ABS sensor

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by yepyep, Apr 1, 2023.

  1. yepyep

    yepyep Bobtail Member

    Apr 1, 2023
    I have a ABS light on the dash. And need to know the way to narrow it down to the one that needs my attention. I am unable to run a check on the truck to find the one at fault. Thanks for any help in advance.
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  3. 86mechanic

    86mechanic Medium Load Member

    Sep 6, 2016
    Northridge, CA
    Get a Multimeter and ohm all the sensors and see which one differs from the others.
    They should be 800-2000 ohms.
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  4. xsetra

    xsetra Road Train Member

    Aug 21, 2011
    What kind of truck and trailer.
    What brand ABS. Most systems have a blink code.
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  5. uncleal13

    uncleal13 Road Train Member

    Apr 9, 2009
    Humboldt, Sk
    Should be able to turn the key on and off a number of times to get the abs light to flash a code. Have to look up the manufacturer of the abs.
    If you can jack up each wheel end, hook up an multimeter to each wheel sensor. Put it on AC volts. Give the wheel a spin and you should get about 0.5 to 1.0 volts ac.
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  6. Rideandrepair

    Rideandrepair Road Train Member

    Aug 8, 2015
    Meanwhile try to push the ones on the steers in. They’re usually easy access. Maybe one of them has slipped out too far away from the tone ring. They suggest a wooden dowel or stick. A 1/4” extension or even a screwdriver tapped lightly works. Just don’t hammer it hard and damage it. Might be able to tap the ones on the drives in, too. Being too far from the tone ring sometimes is caused by a loose wheel bearing. Look at Webasto and Merritor websites Figure out which system you have. Find the procedure to get the code. Different systems different codes. Mine has a switch on the ABS ECU. It’s located under the bunk behind the passenger seat on Freightliner. Hit the switch, and count the flashes on the dash light. Then look up the code. The codes usually a sensor. Before taking a wheel off and changing the sensor. Try to change the wire going to it. The best scenario is if the sensor has a short wire, and an extension wire running from it. You can change it. If it has one long wire from the sensor, the wheel will need to come off to change the whole sensor. The sensor itself rarely goes bad. The wire does. It can also be a bad short wire. In which case the wheel will probably need to be removed to change it. I’ve changed them on my Trailer from the backside. It’s tricky, but can sometimes be done. When changing a sensor on the Tractor, if it’s stuck in place, be careful not to break the aluminum bracket. You’ll have no choice but to pull the wheel off to change it. Once a repair is made, you must Drive the Truck at least 3, maybe 5 mph to reset the code, and turn the light off. If the lights still on, check the code again. Might still have the same code. If it’s a sensor code, and you already replaced the extension wire going to the ecu, probably have a bad short wire from the sensor, or a bad sensor. Might have more than 1 issue. Last code may be gone, and another code pops up. They’re stored in order of event. Last event shows up first. Need to keep diagnosing and fixing till all codes are gone. You can buy one wire the length of the longest one you have on the Truck. Use it for diagnostics. Keep it as a spare if not needed. You can always use it anywhere and bundle the excess length. The websites have good diagnostic information. Take your time and read through it. Looks intimidating at first. Half the battle is identifying your system, might even need to get the part # of the ecu,
    Last edited: Apr 2, 2023
  7. Inderjit

    Inderjit Medium Load Member

    Sep 17, 2017
    What year and make of truck? Air or hydraulic brakes?
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