ABS has become practically standard equipment coming from all vehicles. Sensors tell your working computer when a wheel stops rotating, which indicates-at least should the vehicle really has forward speed-that the brakes have overpowered the available traction during this particular wheel. The pc then directs a hydraulic valve to secrete some brake fluid pressure into the wheel to let it rotate again. This technique repeats more often than not per second up until the vehicle stops or you increase your foot heli-copter flight brake pedal. The ABS computer does a power-on self test any time you cycle the ignition. If it finds it’s lacking data, or perhaps hydraulic pump or valve isn’t responding, it illuminates the ABS warning light within the dash. ABS runs on the properly operating conventional brake system. In case the ABS packs up, you ought to possess normal, unassisted braking, so it’s safe to keep your vacation.
LIGHTS OUT
Your ABS light is on. What to do now? First, remember it really is the ABS light but not light that indicates a problem using your normal service brakes. If there is a normal brake issue, like low pedal or grinding noises, this can be the wrong Saturday Mechanic on your behalf. Make sure your brakes have adequate lining life, aren’t frozen up and are also completely free of air. Mind you, if people must replace your brake fluid, try as hard since you can to prevent getting air within the ABS controller. It’s tough to bleed, and lots of require usage of a scan tool to bleed at all. (The scan tool features a function that cycles the pump and valves to maneuver air from internal passages that can’t be bled properly otherwise.)
In case the light is actually the ABS warning, an important thing to try would be to cycle the ignition key off and back on. It’s like rebooting your computer-and just maybe whatever transient glitch confused the ABS controller has transpired and many types of is well. If ever the condition repeats, you have to do some poking and prodding.
You could have two options as soon as your ABS light stays on. Reduce costs is to find a shop which includes a scan tool which will the decision ABS controller. The dealer has one, as will some aftermarket shops. For the modest fee ($50 to $100), a technician will interrogate your ABS controller and look for a trouble code held in memory. This code will not less than present you with an idea of where you can look.
However, if you’d choose to tear for it yourself along with perhaps find something simple, you’ll require a service manual specific to your car, easy shop tools, with a high-impedance multimeter. The service manual is rather important-if you can’t purchase a paper manual, try subscribing to alldatadiy.com for service data it is possible to download.
On some vehicles, you can access diagnostic trouble codes stored in isn’t even close to without employing a scan tool. Usually this means pulling a connector and shorting two pins having a small jumper. The ABS warning light will blink don / doff in the pattern, equivalent to a trouble code or lack thereof. Obviously, you’ll need a shop manual to aim this. Itrrrs likely you won’t be ready to talk the service manager on the dealer into letting you photocopy his manual-but it’s worth trying. Much of this information and facts are available online-check popularmechanics.com/autodata for suggestions on the best places to hunt for service manuals.
Let’s say you don’t have the trouble code with out information to be other than an illuminated ABS light. Took action now check the fuse to your ABS unit, right? This fuse can be inside the fuse panel into the passenger compartment or underhood. Let’s not skip well-known.
Fuse okay? Look into the service manual for that voltage and resistance values on various pins and sensors. The main harness towards ABS controller is one place you’ll be checking, so while it’s apart, give it a shot of aerosol contact cleaner. Inspect carefully for virtually any symptoms of corrosion-remember the signals traveling down most of these wires just millivolts and any sort of resistance is usually a major impediment. When you can, read the resistance throughout the wheel speed sensors.
Should the ABS controller looks A-Okay, and unplugging and reinserting the primary harness didn’t help, it’s time for you to eyeball the wheel speed sensors-especially if the ABS issue started once a trip by using their snowbank on the mall or after the high-speed trip down a gravel road. Maybe you have damaged the wiring triggering the ABS sensors or perhaps the tone wheels or sensors themselves. Tone wheel? The ABS controller needs to understand how fast each wheel is rotating. Somewhere on each wheel bearing assembly or axle is really a toothed wheel, and there’s a magnetic pickup positioned immediately at the side of it. (Exception: Some rwd vehicles work with a three-channel system while using the tone wheel included in the back differential.) Much more assembly fades in view, it’s at risk of damage from foreign objects.
Loosen the lug nuts or bolts, block and the second wheel and jack up the auto. (You pickup truck owners may be able to crawl under look.) Inspect the wheel speed sensor’s wiring harness additionally, the sensor itself. Some sensors are integrated fairly well into your hub and aren’t more prone to damage. Others simply bolted to stamped brackets. In the event the sensor is loose or missing, or perhaps the wires are damaged, you’ve found your problem. Examine the air gap relating to the sensor and the tone wheel if it’s adjustable-the shop manual can provide a specialized distance the sensor is supposed to be spaced with the tone wheel and directions regarding how to properly set it up. On rare occasions, a negative wheel itself will demonstrate to damage, including missing teeth or teeth damaged by road debris. On front-wheel-drive cars, this means replacing the stub axle, as the tone wheel is machined directly in the axle. When the harness for the sensor incorporates a connector in the wheel well, pull it apart and look the sensor for continuity through an ohmmeter. The resistance value can be obtained from a store manual. Check out shorts to ground also. Repair any bad wiring, remembering that there’s lots of mud, snow and salt-water floating within the wheel well.
