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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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On Feb. 20, the Automotive Service Association (ASA) hosted its monthly Webinar Wednesday.

 

The webinar featured well-known industry trainer “G” Jerry Truglia of Automotive Technicians Training Service, who presented “Why a DTC is Not Always Displayed.” Truglia covered how to alleviate issues related to a check engine light that comes on after the vehicle is repaired and how to diagnose and repair DTCs and drivebility more efficiently.

 

ASA Vice President Tony Molla began by welcoming attendees and introducing Truglia. Truglia began by examining the right way to diagnose DTCs and drivability problems. He noted that the most important tool needed to diagnose DTCs is a generic/global scan tool, but a factory scan tool is not always necessary.

 

He stated, “You’re not going to become an expert in an hour, but we can put some lights on and help each other.”

 

Repairers also need a game plan. Truglia explained, “Information on iATN, Identifix, ALLDATA, Mitchell, Autodata, MotoLogic, or even Google and YouTube can be very helpful in identifying if the vehicle you are working on needs a reflash or has a silver bullet problem. Remember, when looking at a silver bullet solution, always check and test the components and the system before replacing anything.”

 

As he began to explain how to understand the diagnostic process, Truglia noted, “Before we go too deep, let’s get the caveats out of the way. When it comes to diagnosing engine performance, DTCs or driveability problems use a general/global scan tool to expedite your diagnosis. A general/global OBD II scan tool allows us to view information quickly while allowing access to pending DTCs, Monitors, Mode 6, Mode 10 and Freeze Frame, to name a few. You won’t get all that information in the enhanced side of your scan tool, so start with the generic/global side first, and if you need more data PIDs or bi-directional control, switch to the enhanced side. Also, general/global PIDs are the same on every vehicle, whether it’s a GM, Toyota or a BMW. The data PIDs are all the same and easier to understand.”


 

Truglia explained that repairers can get factory scan tool capabilities with J2534 and LSID/VSP, and he encouraged everyone to sign up at nastf.org because “when you replace just about any computer on today’s vehicles, you’ll need that information to get the vehicle back online.”

Displaying a slide that showed the modes of the OBD II, Truglia pointed out that this is the powertrain data that everyone has been looking at for years. He emphasized the importance of Mode 6, Mode 9 and Mode 10.

 

“Mode 9 is super important because it gives us VIN information and allows us to see calibration files. Mode 10 will give us information that is stored in computer systems. This information is only erased after the vehicle has passed multiple times in special criteria,” he said.

 

Truglia proceeded to demonstrate how to use the scan tool’s different modes, providing examples of scans and discussing what each of them could mean.

 

Truglia explained, “If a monitor is not ready and you give the vehicle back to the customer without telling them, the client may get their check engine light illuminated again, and they won’t know whether it’s on for something they already paid to fix. I recommend that you print these screens and give them to the customer.”

 

Reminding everyone to use the generic/global OBD II first, Truglia noted that generic scan tools cannot substitute a value like an enhanced tool can. He talked through selecting the correct PIDs that should be viewed, pointing out that generic tools don’t have as many so they are less confusing.

 

Truglia then moved on to discussing scan data fuel trim and the importance of knowing the good and bad limits so imbalances in the engine can be identified. He walked through many examples and explained the different issues that can be identified with this data.

 

He noted, “Why does the number of fuel trim make a difference? Knowing which cell lets us know what and where to look for problems. Most mapping systems use a total of 16 cells, while some others will use a few more for other cells for fuel cut off, power enrichment, and EVAP purge, to name a few. Looking at RPM and map or load, you can see the difference of how we add or subtract fuel using fuel trim cell data.


 

“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.”


 

Discussing the PIDs that absolutely need to be viewed, Truglia explained that graphing PIDs helps problems stand out. He recommended looking at the LTFT, MAF, MAP, Calculated Load and when checking for a P0420 and P0430 catalyst efficiency DTCs. He recommended graphing the front O2 or air fuel sensor along with the rear O2 sensor at idle, 2000 and 3000 rpms to make sure that the rear O2 sensor does not dither. This efficiency test will uncover a potential issue that causes the P0420 and P0430 DTCs.

 

Regarding time to temperature, Truglia pointed out, “This tells us if the engine is warming up too slowly or too fast. If the thermostat doesn’t open at the right pace, there could be transmission or drivebility issues. Be assured that you need to look at time to temperature.”

 

After providing several more case studies, Truglia advised that CO2 and the ATS Bulleye leak detection tool, along with thermal imaging, can be helpful tools for some DTCs and how to find problems.

 

He ended his presentation by reminding participants, “Don’t just look at the DTCs. Look at all of the information that’s available to you. That’s the moral of the story here.”

 

Molla then resumed control of the broadcast and led a question-and-answer session based on attendees’ feedback. ASA will host a bonus webinar on Feb. 27 on “How Engaging with AMi can Increase Profits” with AMi President Jeff Peevy.

 

On March 20, ASA’s Webinar Wednesday will feature Robert L. Redding Jr., ASA legislative representative for the D.C. office. He will provide an update on the 2019 state legislative sessions and shop-relevant items on the legislative agenda.

 

For more information on ASA, visit asashop.org.