Anti-Lock Braking System - General Information

[567chevys]

Your anti-lock braking system is versatile, technical apparatus that can help you brake better and safer. It does this by helping prevent your brakes from locking up. Note: not all vehicles have anti-lock brakes. Anti-lock brakes are standard on some vehicles and can be ordered as an option on others.

Note: this is a general description. Consult a repair manual or other reference material written specifically for your truck, car, SUV or van for an exact description of your anti-lock brake system.

Your anti-lock brake system (ABS) helps maintain directional stability, vehicular steering, and optimum deceleration under extreme braking conditions on many types of surfaces. These include icy, wet and gravel-covered roads. The system does this by monitoring each wheel's rotational speed and by controlling brake-line pressure to each wheel's brakes during braking. These actions together prevent the wheels from locking up.

The ABS has three main components: 1) a speed sensor on each wheel 2) an electronic control unit and 3) a hydraulic unit. The system works like this. The four wheel sensors, one on each wheel, routinely send electronic signals to the control unit. The control unit monitors and compares these signals to its internal program, making a determination as to whether a wheel is about to lock up.

If the control unit senses that a wheel is about to lock up, it sends an electronic signal to the hydraulic unit, telling the unit to reduce hydraulic pressure (or keep it at the current level). The braking unit at the wheel receives this electronic signal at the brake caliper. Electronically-operated solenoid valves control hydraulic pressure to the brakes.

If a problem develops in the system, an ABS warning light will illuminate on your dashboard. Visually inspecting the ABS will sometimes help locate the problem. Carefully inspect the wheel sensor wiring harness. Pay special attention to the harness and the connections near each wheel. Watch for signs of chafing or breaks. This could be caused by the wires being incorrectly routed. If the wheel-sensor wiring harness is damaged in any way, the sensor must be replaced.

Warning: Do not try to repair an ABS wiring harness. Your ABS is very sensitive to even the slightest change in electrical charges. Repairing the harness could alter the electrical impulses flowing through the harness and cause the ABS to malfunction. If your ABS wiring harness is damaged in any way, replace it.

It is possible to diagnose and repair a malfunctioning ABS yourself. However, if you have any doubts or concerns about your ABS and you are not inclined to attempt what could be an involved diagnosis and repair procedure, take your vehicle to a qualified automotive technician.

[warren57]

Just bought my granddaughter a 79 Olds. Car was in great shape, ran good, everything....except the ABS light and Traction Control light stayed on. I wanted to get them working so she would have the best protection possible. Read everything I could find on the internet, Put new disc pads on, checked brake fluid level and was running out of easy fixes. Called a friend that is the service manager at a local Chevy dealer and asked him if he could check it out for me. Just before I took it to him, I checked every inch of the wheel sensor wiring. Well, the left front was pulled out of the harness and had no connector attached. I went to pull and pay auto and found the same model car, removed the wire ($3.00) went home, installed it, everything works perfect.
Moral of the story, (as you stated) check the wires and connectors !!

[chevynut]

I assume you got this from some website or article:

Warning: Do not try to repair an ABS wiring harness. Your ABS is very sensitive to even the slightest change in electrical charges. Repairing the harness could alter the electrical impulses flowing through the harness and cause the ABS to malfunction. If your ABS wiring harness is damaged in any way, replace it.

I'm not sure I understand what the big deal is. The ABS sensors are Hall-effect sensors, I believe, and the controller is digital. So what "electical charges" are they referring to? As far as I know, you're just dealing with electrical pulses. I wouldn't hesitate repairing an ABS harness myself.

[Rick_L]

There was a similar internet admonition on O2 sensor wiring. Something about air flowing through the wire with the insulation acting like a hose.

I guess there are those that when they don't understand something they just make something up.

[chevynut]

An O2 sensor actually outputs an analog signal, so I can see the importance of maintaining integrity of the wiring to it. But there is such little current flow that I don't know if a bad connection would even make that much difference in the signal. You can say the same thing about most engine sensors, since they're analog as well (0-5 volts typically).

Lots of "old wives tales" out there that are hard to disspel....like the one about putting a restrictor in your cooling system to improve cooling. LMAO!

Don't get me started.......

[Rick_L]

So you believe the bit about the airflow through the wire insulation? Which direction does it flow? How does that affect voltage?

[Romax55]

We should keep our guard up when reading anything that's sales-oriented , like the BS about not repairing ABS sensor wiring . Being skeptical is what fuelled the whole hotrodding industry , and I'm afraid I'm more than skeptical about this kind of literature now ; I'm downright suspicious , to the point of wanting to chop off a few O2 sensors in the laneway , and solder them back up . I know the ABS sensors can be repaired successfully ; I just fixed both front sensors on an 05 Dodge Caravan , and get no codes from either ECM or ABS modules . That business about the airflow in an O2 sensod harness is just unbelievable . Be safe...Bob.

[chevynut]

So you believe the bit about the airflow through the wire insulation? Which direction does it flow? How does that affect voltage?

That's total bullshit, imo.

[Rick_L]

Just checkin', you had me worried for about a nanosecond. Never know what you'll read in those AARP sales pitches.