Diagnosis Using A Labscope

THE GOLDEN RULE OF ELECTRONIC SYSTEM DIAGNOSIS IS:

For the vehicle's computer system to function properly, it must receive signals with the dimensions it was designed to communicate with.

In other words, for the vehicle's computer system to function properly, it must be able to "read" and "write" the universal language of intelligent electronic communication. By using the Digital Storage Oscilloscope (DSO), we will electronically "eavesdrop" on the vehicle's electronic conversations, both to pinpoint problems, and to verify that all is well after repairs have been performed. If a sensor, actuator or even the PCM is not generating electronic signals with the correct Critical Dimensions, then the circuit can suffer from a "communication breakdown," which can surface as a driveability problem, emissions failure, or in some cases, set a DTC (Diagnostic Trouble Code).






Each of the five primary types of electronic signals use the "electronic words" or "Critical Dimensions," to establish electronic communication. One of the five primary types of signals uses only one "electronic word" to communicate, another uses only three "electronic words" to communicate, and another uses four and so on. Study the table above to get a better understanding of which types of signals use which types of "Critical Dimensions" to do their "electronic communication." Don't worry too much about taking all of this in and completely understanding it for the moment. We will cover this further in the component tests. For now, just think of the "Critical Dimensions" as "electronic words" and imagine that the more words you can use, the more complex "electronic sentences" you can make up.

As you can see, the further you get down the list of the five signal types, the more "electronic words" they use to communicate. "Electronic Communications" language is a lot like speaking languages in another aspect worth noting exceptions. The above rules work very well and hold up in most cases, but just like some words in the English language don't sound like they are spelled, "Electronic Communications" language has exceptions to its rules too. Not many, but there are a few. We will get to those as we go.

It may come as no surprise to some that Serial Data signals, the signals that PCMs and other "electronically intelligent" devices use to communicate, are the most complex signals in the vehicle. Serial Data Signals contain the most complex "electronic sentences" in the vehicle. In fact, they take a special analyzer to "decode" them one very familiar to us the scan tool.