As I was driving out of the house recently, suddenly realise that the ABS indicator on the instrument cluster of my vehicle lit-up. I was actually on my way to the garage, so I decided to it take into the workshop for a diagnostic scan.
The codes retrieved from the system was C1200: Wheel Speed Sensor Front Left Open/Short.
Possible causes could include, but not limited to (a) Faulty Wheel Speed Sensor Front Left (b) Wheel Speed Sensor Front Left harness is open or shorted (c) Wheel Speed Sensor Front Left circuit poor electrical connection.
Instinctively, the first thing I did was to carry out “live data streaming”. This is a process whereby live information is being retrieved from a component on the vehicle while being operational. The result of that was an incoherent speed sensor.
The next step was to take out the wheel on that side to visually inspect the sensor for chaffing or other forms of obvious damage. Upon inspection, everything seemed to be intact. I took it a step further by disconnecting the sensor from the wire harness and removing it from the wheel to visually inspect it for possible fouling, everything seems intact as well.
Several vehicle owners have been and are driving around with an ABS indicator illuminated on their instrument cluster. Often times people say “but my brake still works well, so why would I bother myself trying to fix a non-existent problem”
Let me tell you a bit about the ABS. ABS is an automated system that uses the principles of threshold braking and cadence braking techniques which were once practised by skillful drivers before the technology became widespread. ABS operates at a much faster rate and more effectively than most drivers could manage. Although, ABS generally offers improved vehicle control and decreases stopping distances on dry and some slippery surfaces, on loose gravel ABS may significantly increase braking distance, while still improving steering control. Since ABS was introduced in production vehicles, such systems have become increasingly sophisticated and effective. Modern versions may not only prevent wheel lock under braking but may also alter the front-to-rear brake bias. This latter function, depending on its specific capabilities and implementation, is known variously as electronic brakeforce distribution, traction control system, emergency brake assist, or electronic stability control (ESC).
There are many different variations and control algorithms for ABS systems. Let’s discuss how one of the simpler systems works.
The controller monitors the speed sensors at all times. It is looking for decelerations in the wheel that are out of the ordinary. Right before a wheel locks up, it will experience a rapid deceleration. If left unchecked, the wheel would stop much more quickly than any car could. It might take a car five seconds to stop from 100Km/h under ideal conditions, but a wheel that locks up could stop spinning in less than a second.
The ABS controller knows that such a rapid deceleration is impossible, so it reduces the pressure to that brake until it sees an acceleration, then it increases the pressure until it sees the deceleration again. It can do this very quickly before the tire can actually significantly change speed. The result is that the tire slows down at the same rate as the car, with the brakes keeping the tires very near the point at which they will start to lock up. This gives the system maximum braking power.
When the ABS system is in operation you will feel a pulsing in the brake pedal; this comes from the rapid opening and closing of the valves. Some ABS systems can cycle up to 15 times per second.
Cool right? back to my story. It has become obvious now that I need a new sensor for the affected wheel.
The story of how I got to purchase the replacement is for another day. I however did and installed it. The indicator went off and stayed off immediately the engine was started and has remained so since. Worthy of note is that I feel the ABS kicking-in every time I expect it to.
That was how I solved my ABS problem.
I hope this particular topic would actually prompt someone out there with an ABS problem that has been ignoring it for years to actually consider solving the problem.
Yes, it is possible that the solution may not be as easy as mine. The ABS has other components that could go bad or get damaged. A specific cost can’t be put on life(s) that could be lost should a vehicle lose braking power.
I also hope this inspires mechanics who believe that ABS issue(s) is/are something that can just be passed-on since the vehicle can run without it.
Till I come your way again next week discussing something that is equally important, I hope my story and experience will inspire somebody to actually do the needful.