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Tuesday, 26 February 2019 21:59

ASA Webinar Features ‘G’ Jerry Truglia’s ‘Why a DTC is Not Always Displayed’

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“If fuel trim is normal, you can see there’s no problem, but don’t forget to look at the monitors so you don’t have a customer problem. Use data to determine what the problem is and which cell the problem is located in. The problem is with the load sensor most of the time. If we don’t have enough voltage at a component, it could be a power or a ground problem right, then we have an issue. These things are sometimes masked so you don’t see a directly related DTC.”

 

Truglia demonstrated how Mode 6 shows the minimum and maximum values. The goal is to have a value in between, which would indicate that the item is working well.

 

“Mode 6 is a quiz that fails a number of times; it then turns into a pending DTC,” he explained. “It means that if the item failed enough times in Mode 6, it is escalated to a pending DTC, then on to a DTC. Remember: If it continues to fail as a pending DTC, it will turn into a DTC and cause a check engine light to illuminate. Use Mode 6 to predict what’s going to happen to that vehicle. Go to the test results to figure out which areas have possible concerns.”

 

Truglia went on to explore Mode 10 and looking at permanent DTCs if the codes are already erased. He also stressed the value of looking at relative compression to become alerted to possible mechanical problems.

 

He emphasized, “Never erases DTCs. It’s like pouring Clorox on a crime scene---nothing will be revealed.”

 

Many examples were provided via screenshots as Truglia talked through what repairers should pay particular attention to in specific scenarios. Explaining how to understand O2 – AFR voltage levels, Truglia noted, “The lower the AF sensor voltage, the richer the mixture, while the higher the voltage, the leaner the engine is running. This is opposite of what we’re normally used to, so take note of that.”