Important: Use custom search function to get better results from our thousands of pages

Use " " for compulsory search eg:"electronics seminar" , use -" " for filter something eg: "electronics seminar" -"/tag/" (used for exclude results from tag pages)
Tags: Troubleshooting, Antilock, Braking, troubleshooting auto problems, troubleshooting air conditioners, troubleshooting abs brakes, troubleshooting air conditioning, troubleshooting automatic transmission, troubleshooting a computer, troubleshooting a furnace, troubleshooting auto air conditioning, troubleshooting a pc, troubleshooting air conditioner problems, troubleshooting car problems, troubleshooting computer problems, troubleshooting computers,
Ask More Info Of  A Seminar Ask More Info Of A Project Post Reply  Follow us on Twitter
21-09-2008, 09:30 AM
Post: #1
Troubleshooting Antilock Braking
Troubleshooting Antilock Braking
[Image: 2202008182947.jpg]

Use your trusty multimeter to check continuity through wheel speed sensors.
This sensor has a value of about 1.5 K ohms.

By Mike Allen
Photography by James Westman
Published in the February 2006 issue.

Over the river and through the woods was more dangerous back when cars had crummy bias-ply tires, rear-wheel drive and ordinary brakes. So, tonight you feel confident driving home through several inches of freshly fallen snow after a sumptuous holiday dinner. Your front-drive car has excellent all-season tires and ABS (antilock braking system)--although the ABS light has been on since you banzai'd the berm at the end of the driveway an hour ago. This may explain the loss of steering control when you're slowing down for a corner. Like this downhill turn, right ... there, as you blow straight past it with the wheels skidding and the steering cranked over hard against the stop.

ABS has become pretty much standard equipment on most vehicles. Sensors tell a computer when a wheel stops rotating, which indicates--at least when the vehicle still has forward speed--that the brakes have overpowered the available traction at that particular wheel. The computer then directs a hydraulic valve to release some brake fluid pressure to the wheel to let it rotate again. This process repeats many times per second until the vehicle stops or you lift your foot off the brake pedal. The ABS computer does a power-on self test every time you cycle the ignition. If it finds it's lacking data, or a hydraulic pump or valve isn't responding, it illuminates the ABS warning light on the dash. ABS relies on a properly operating conventional brake system. If the ABS packs up, you should still have normal, unassisted braking, so it's safe to continue your journey.


Broken or corroded wires to the sensor are a common ABS problem. A piece of rope on the street got wound around the hub to pull these apart.

? For background information on how anti-lock brakes work,

LIGHTS OUT
Your ABS light is on. Now what? First, be sure it really is the ABS light and not the light that indicates an issue with your normal service brakes. If you do have a conventional brake issue, like low pedal or grinding noises, this is the wrong Saturday Mechanic for you. Be sure your brakes have adequate lining life, aren't frozen up and are completely free of air. By the way, if you ever need to replace your brake fluid, try as hard as you can to avoid getting air into the ABS controller. It's difficult to bleed, and many require the use of a scan tool to bleed at all. (The scan tool has a function that cycles the pump and valves to move air out of internal passages that can't be bled properly otherwise.)

If the light really is the ABS warning, the first thing to try is 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 passed and all is well. If the condition repeats, you need to do some poking and prodding.

You have two options when your ABS light stays on. The first one is to find a shop with a scan tool that will talk to your ABS controller. The dealer will have one, as will some aftermarket shops. For a modest service fee ($50 to $100), a technician will interrogate your ABS controller and look for a trouble code stored in memory. This code will at least give you some idea of where to look.


Inspect the tone wheel and speed sensor for damage from foreign objects. The gap between them is crucial.

Spray contact cleaner into the connection to the ABS computer if there's any evidence of corrosion or dirt.

But if you'd like to tear into it yourself and maybe find something simple, you'll need a service manual specific to your car or truck, and simple shop tools, including a high-impedance multimeter. The service manual is extremely important--if you can't get a paper manual, try subscribing to alldatadiy.com for service data you can download.

On some vehicles, you can access diagnostic trouble codes stored in the computer without using a scan tool. Usually this means pulling a connector and shorting two pins with a small jumper. The ABS warning light will blink on and off in a pattern, corresponding to a trouble code or lack thereof. Obviously, you'll need a shop manual to attempt this. Odds are you won't be able to talk the service manager at the dealer into letting you photocopy his manual--but it's worth a try. Much of this data is available online--check popularmechanics.com/autodata for suggestions on where to look for service manuals.

Let's say you don't have the trouble code and no information to go on other than an illuminated ABS light. You did check the fuse for the ABS unit, right? This fuse may be in the fuse panel inside the passenger compartment or underhood. Let's not skip the obvious.

Fuse okay? Check the service manual for the voltage and resistance values on various pins and sensors. The main harness to the 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 any signs of corrosion--remember that the signals traveling down some of these wires are only millivolts and almost any resistance is a major impediment. If you can, check the resistance across the wheel speed sensors.

If the ABS controller looks A-Okay, and unplugging and reinserting the main harness didn't help, it's time to eyeball the wheel speed sensors--especially if your ABS issue started right after a trip through that snowbank at the mall or after a high-speed trip down a gravel road. You may have damaged the wiring leading to the ABS sensors or even the tone wheels or sensors themselves. Tone wheel? The ABS controller needs to know how fast each wheel is rotating. Somewhere on each wheel bearing assembly or axle is a toothed wheel, and there's a magnetic pickup positioned immediately next to it. (Exception: Some rwd vehicles use a three-channel system with the tone wheel built into the rear differential.) Because this assembly is out in the open, it's prone to damage from foreign objects.

Loosen the lug nuts or bolts, block the opposite wheel and jack up the car. (You pickup truck owners may be able to crawl under and check.) Inspect the wheel speed sensor's wiring harness and the sensor itself. Some sensors are integrated fairly well into the hub and aren't prone to damage. Others are simply bolted to stamped brackets. If the sensor is loose or missing, or the wires are damaged, you've found your problem. Check the air gap between the sensor and the tone wheel if it's adjustable--the shop manual will give you a specific distance the sensor is supposed to be spaced from the tone wheel and directions on how to properly set it. On rare occasions, the tone wheel itself will show damage, such as missing teeth or teeth damaged by road debris. On front-wheel-drive cars, this usually means replacing the stub axle, because the tone wheel is machined directly onto the axle. If the harness to the sensor has a connector in the wheel well, pull it apart and check the sensor for continuity with an ohmmeter. The resistance value can be found in the shop manual. Check for shorts to ground as well. Repair any bad wiring, remembering that there's plenty of mud, snow and salt water flying around in the wheel well.

TIME'S UP
If you've checked all the sensors and wiring and the ABS light still glows, it's time to throw in the towel and start looking seriously at the ABS controller, an amalgam of hydraulics and electronics that has, as they say, no user-serviceable parts inside. It is, predictably, expensive. Replace it as a last resort.

Consult your service manual for a chart of specific values and pinouts to check against, which should help you narrow down the problem to a specific wire or sensor. This chart is typical.

Antilock Quick Test Check Sheet Using Rotunda 60-pin EEC-IV Breakout Box 0 14-00322 or equivalent
Item To Be Tested Ignition Mode Measure Between Pins Tester Scale/Range Specification Pinpoint Test
Power Feed
Battery Check off batt. Terminals volts 10 minimum
ABS ECU Power on 14 + 1 volts 10 minimum DTC B 1318
Pump Motor Power off 2 + 1 volts 10 minimum DTC C 1095
Valve Power off 13 + 1 volts 10 minimum DTC C 1266
Sensor Resistance
LF Sensor Resistance off 15 + 16 K ohms 1.28-1.92 K ohms A
RF Sensor Resistance off 20 + 7 K ohms 1.28-1.92 K ohms B
LR Sensor Resistance off 17 + 18 K ohms 1.28-1.92 K ohms C
RR Sensor Resistance off 4 + 19 K ohms 1.28-1.92 K ohms D
Sensor Continuity to Ground
LF to Ground off 15 + 1 continuity no continuity A
RF to Ground off 20 + 1 continuity no continuity B
LR to Ground off 17 + 1 continuity no continuity C
RR to Ground off 4 + 1 continuity no continuity D
Sensor Output Voltage
Rotate Wheels at One Revolution Per Second
LF Sensor Output off 15 + 16 AC mV > 100 mV A
RF Sensor Output off 20 + 7 AC mV > 100 mV B
LR Sensor Output off 17 + 18 AC mV > 100 mV C
RR Sensor Output off 4 + 19 AC mV > 100 mV D
ABS Warning Lamp Check on 22 + 1 volts 10V minimum E
Stoplamp Switch Check
Brake Pedal Applied off 9 + 1 volts 10 minimum
Brake Pedal Released off 9 + 1 continuity no continuity

Please Use Search http://www.seminarprojects.com/search.php wisely To Get More Information About A Seminar Or Project Topic
Rating Troubleshooting Antilock Braking Options
Share Troubleshooting Antilock Braking To Your Friends :- Seminar Topics Bookmark
Post Reply 

Marked Categories : troubleshooting seminar topic, powered by mybb troubleshooting computer problems, car brakes troubleshooting pdf, where to connect rotunda 60 pin eec iv breakout box 0 14 00322, troubleshooting seminar topics, anti lock braking sensors, wheel bearing spindle 4wheeler assembly ppt, powered by mybb how to bleed brakes, anti lock braking sensors pdf presentation, anti lock braking sensors seminar, popularmechanics com autodata service manual, mech seminar topics, mechanical seminar topics,

[-]
Quick Reply
Message
Type your reply to this message here.


Image Verification
Image Verification
(case insensitive)
Please enter the text within the image on the left in to the text box below. This process is used to prevent automated posts.

Possibly Related Threads...
Thread: Author Replies: Views: Last Post
  Regenerative Braking System Seminar Report seminar code 0 99 15-09-2014 02:04 PM
Last Post: seminar code
  REGENERATIVE BRAKING SYSTEM SEMINAR REPORT project maker 0 108 12-09-2014 03:20 PM
Last Post: project maker
  AUTOMATIC BRAKING SYSTEM FRONT AND BACK SEMINAR REPORT seminar code 0 88 29-08-2014 03:16 PM
Last Post: seminar code
  EPM Braking:Electric pulse Magnetic Braking full report project topics 5 4,345 11-08-2014 12:11 PM
Last Post: Guest
  Braking System:- project maker 0 144 08-08-2014 12:18 PM
Last Post: project maker
  SENSOTRANICS BRAKING CONTROL seminar code 0 103 31-07-2014 11:10 AM
Last Post: seminar code
  Advanced Technology of Automatic Speed Braking System using RF Controllers seminar code 0 181 22-07-2014 02:46 PM
Last Post: seminar code
  ANTI-LOCK BRAKING SYSTEMS IN CARS” project maker 0 134 15-07-2014 03:42 PM
Last Post: project maker
  Automatic Acceleration Control and Braking System (AACBS) Report seminar post 0 212 26-05-2014 11:16 AM
Last Post: seminar post
  A SEMINAR ON REGENERATIVE BRAKING SYSTEM ppt seminar projects maker 0 156 25-04-2014 11:52 AM
Last Post: seminar projects maker
This Page May Contain What is Troubleshooting Antilock Braking And Latest Information/News About Troubleshooting Antilock Braking,If Not ...Use Search to get more info about Troubleshooting Antilock Braking Or Ask Here

Options: