The advent of OBDII scanning ushered in ease, allowing auto-technicians to simply plug-in and run diagnosis to uncover identified problems in a short frame of time. As opposed to conventional trial and error techniques, this method of diagnosis doesn’t fully depend on experience and documentation of re-occurring car problems over the years. In this technological system, several types and grades of scanners directly communicate with the ECU (brain box) to retrieve trouble codes that represent problems in certain car areas. This ideally serves as a guide for mechanics on what to do, not necessarily giving specifics on how to solve a problem. So one can’t totally shove aside the role experience and prior basic technical training plays in how well these information are interpreted by auto-technicians. Also, the type of steps they subsequently take in a bid to curbing the problem.

On these grounds, one can safely point out the fact that OBDII scanners are not stand-alone problem solvers; a sophisticated scanning tool in the hands of an in-experienced or untrained technician is nothing but an expensive toy in the wrongs hands.

It’s also important to point out that these diagnostic machines are in grades, with different levels of versatility and adaptability. This is evident in the flexibility of machines over a wide range of car brands and also, the ability of these electronic diagnostic tools to uncover problems in more complex areas of a car by communicating better with more sub-systems via the CAN/LIN network linked to the ECU.

Having a better understanding of how a modern car systems works is primary to comprehending the true level of ease OBDII scanning offers because, many auto-mechanics today perceive the guiding tools as messiahs.

Just like your nose is connected to your brain, a typical ECU is connected to various sensors and actuators. In event of you perceiving an awful smell, you might voluntarily react by using your hand to block your nose from further taking in a likely poisonous gas or substance. In this simple case, your nose is the sensor whilst your hand is the actuator! A similar case applies to cars, because an ECU can’t record data about car areas it can’t sense, hence OBD scanners can’t detect problems in areas of a car without some level of electronics linked to the ECU by data buses.

The basic trick here is the infusion of electronics in some formerly fully mechanical systems or components, which enhance the role of that area in the general operation of the car. An example is the front brake-pad level sensor in recent Audi models which notify car owners when the brake pads are below specified permissible levels. This is only possible because sensors have been attached to the mechanical brake system. It’s interesting to note that these sensors in place allow for other closely related problem detection like excessive rotor wear.

So just to remind you once again; if there are no electronics, OBD scanners can’t retrieve trouble codes, because the ECU can only monitor areas it can sense or monitor.

The two hurdles that limit how much information one can get using an OBDII scanner are the sophistication of both the car and the machine. The best combo in achieving substantial maximization of this technological trend is using very sophisticated and versatile OBDII scanners with highly computerized cars. Anything other than this, mechanics have to augment the information gap by employing more traditional diagnostic methods to identify problems quicker.
source:http://www.autobaseafrica.com/more-facts-about-obdii-scanning/