Magazine for the auto service professional
Issue link: http://asp.epubxp.com/i/780462
20 | ASP February 2017 Technical Engine diagnostics Should OBD-II be your first step in diagnosing an engine management issue? Yes, and here's why... By Jeff Taylor W e can't possibly have all the tools that we need to repair every vehicle that comes into our shop, even if we concentrate on only a couple of makes or manufacturers. ere are simply too many dedicated tools required today to perform all of the required tasks on today's engine, transmission and drivetrain systems. Even a simple water pump service can now require highly specialized tools, but deal- ing with a check engine light doesn't always require the factory scan tool, even if you have one available. It's important to remember that the OBD-II system's responsibility is to turn on the check engine light and alert the driver if there is a failure in the vehicle's emission control systems, and it's this fact that made me change my diagnostic approach. I typically start to diagnose a check engine light (malfunction indicator light/MIL), by grabbing one of my generic scanners first. I check the OBD-II system to see what infor- mation is available to properly diagnose the issue, allowing me to base my decision on this data. Will I need a factory scanner (that I may or may not have access to) or tell the customer that I don't have the factory scan tool needed and possibly send them back to the dealer? ere are times that you are going to need a factory tool to complete a diagnostic or need some form of bidirectional control, but research has shown that almost 85% of the emissions-related MIL complaints can be dealt with using nothing more than an OBD-II diagnostic capable scanner. For example, intake air temperature and coolant temperature should have similar readings after a cold soak. e OBD-II system also has to keep track of these test results, the operating conditions when it ran the tests and other information that can potentially be used to diagnose a MIL light issue. ere are 10 diagnostic modes to OBD-II that we can use and these modes are typically available on that generic scanner that you already have, but it's important to understand what information each of these modes provides us and how to interpret that information so we can use it in our diagnostic process. Mode $01... Request the current pow- ertrain diagnostic data. (e $ sign in the When a check engine light comes on, having a game plan for understanding the cause and fixing it quickly is critical for your customer's satisfaction and profitability for you. Having the correct scan tools at your disposal and running through the 10 diagnostic modes to OBD-II are keys to your success.