Aftermarket October 2022

BY Frank Massey T he most important first step begins with vehicle and owner triage. Listen carefully, ask searching and relevant questions regarding the complaint, do not accept anything until you have confirmed the condition, and never accept previous work or opinion as correct. The customer must accept this cost or walk away. The triage may include, visual inspection, road test, or a preliminary global vehicle scan, i.e., all systems. None of this is free. It is part of a progressive methodical process. Agree a separate contract for this allowing either party to walk away. One especially crucial point to understand before you begin any repair or diagnostic investigation, you must fully understand how the system functions and the specific responsibility of each component in that system, how it operates and how to test it. Check DTCs that are relevant to the symptoms, not 24 AFTERMARKET OCTOBER 2022 TECHNICAL www.aftermarketonline.net BUILDING THE BETTER GARAGE In the second part of his look at how to put together your diagnostic service offering, Frank looks at how you should always work to a plan forgetting pending and confirmed errors in EOBD. Also check for incomplete default flags. These cannot be cleared unless all flag parameters have been satisfied during drive cycles. Next, you need to cross-reference specified, actual, and corrected data. A fault code will not register unless the component parameters have been exceeded, in some cases for a considerable time, so fast intermittent drive concerns may not be registered in the fault memory. Previous experience over the past 50 years has convinced me of the value in using gauges when confirming, fluid, pressure, and flow. For example, when testing fuel pump performance, flow is just as important as pressure. Also check the pump current. It is linear with pressure, therefore faults may be predicted by checking current across the relay or fuse without accessing the pump or supply hoses. Intermittent variable vane turbo faults are easily monitored Pico NVH WPS PART TWO