But the ECM is no longer the only onboard computer. Modern cars are equipped with dozens of control modules, each tasked with controlling a different system. There’s one for the HVAC system, one for the body – even one for each power window! To complicate things further, they communicate with one another over a data bus.
Needless to say, special equipment – as well as a great deal of knowledge – is needed to diagnose and repair these vast electronic networks. Although each module is designed to store a code when it detects a problem, this information isn’t an actual diagnosis. It merely serves as a starting place for further analysis. Hours of tedious troubleshooting may be needed to determine the actual problem.
These days, electronic components such as computers, sensors, and actuators are integrated with traditional mechanical parts. There’s no way to separate the two completely. Because of this, nearly any type of problem – from a harsh shifting transmission to a broken HVAC system – can be caused by onboard electronics. Depending on the failure, these units may or may not turn on a warning light (ABS, EPS, etc.). A diagnostic code is usually stored, but not always.
