![]() Professional technicians, on the other hand, need a scan tool with advanced capabilities that is both affordable when they buy it and when they update it for future models. ![]() It would also be a big plus if the tool also helped determine what repairs are needed to solve the problem. Many modern scan tools have a vast library of repair solutions that can provide the user with the information he or she needs for a solid diagnosis.ĭo-it-yourselfers want a scan tool that is affordable and makes it easy to diagnose what caused the MIL to come on. There is a large selection of scan tools for everyone from the do-it-yourselfer to the professional technician at prices that range from very inexpensive to multi-thousands of dollars. ![]() The scan tool is always the first thing to use in a MIL-on, or a driveability-complaint situation. ![]() When the PCM detects a malfunction with any monitored system, it will set a DTC (Diagnostic Trouble Code) and turn on the MIL (Malfunction Indicator Lamp), but you can also have malfunctions that will not set a code. Sometimes the computer is referencing data that contains enough out-of-range readings to create a driveability problem, yet it may not trigger a DTC, or turn on the MIL.Īn old saying from the computer world that very much applies to an automotive PCM is “garbage in, garbage out.” If the input data from the various sensors the PCM monitors contains errors (“garbage in”), the PCM will process the faulty data, then send commands that are not appropriate (“garbage out”). Whenever you’re diagnosing a vehicle, you should always check for any DTCs and review all of the data stream readings to be sure that everything is within the correct operating range. Therefore, you should not assume that because the MIL is not lit that everything is okay. The input data from the various sensors must be correct if the PCM is going to provide helpful output commands. The PCM is performing operations that would have been all but impossible not that many years ago, but you still need to remember it is just a computer. Olsen The PCM (Powertrain Control Module) monitors and controls just about every aspect of a modern vehicle’s operation including such things as throttle activation, air/fuel mixture, ignition spark advance, variable valve timing, drivetrain response, etc. The best pro-level versions are incredibly powerful now, but there are much less expensive specimens that are very practical, too by Henry P. ![]() What’s the PCM Seeing and Doing? These wonderful diagnostic devices have been around since the early ‘80s. ![]()
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