Here are two examples of how a technician was able to use an oscilloscope to quickly and accurately diagnosis vehicle problems. These come from a technician who took the advanced diagnostics course offered by the Utah Trucking Association, using WheelTime University training.
- Example 1 – The technician was working on a 2016 Freightliner that showed a number of faults under the heading J1939, headway controller.
“I thought it was an overloaded ‘Bus’ situation. I hooked up the scope and got a lot of messages that I was able to decode. What the scope told me is that I was wrong.
“Turns out the J1939 headway controller is how the DDDL8 interprets the radar on the front of the tractor. That led us to find an intermittent fault on the ABS system that was causing the adaptive cruise to fault out. The faulting of the adaptive cruise repeatedly over time turns into a check engine light.
“We fixed it and sent the truck on its way. Without the scope, I would have said ‘communication fault’ and shipped the truck to the dealer.”
- Example 2 – The technician was working on a 2015 Kenworth. The complaint was that the dashboard died and the Qualcomm wasn’t working. There was no other information.
“I ignored the Qualcomm and began investigating the dashboard. None of the gauges would work, except for the center informational area. The Jake brake and cruise control switches were unresponsive.
“First, I logged in with Cummins Insite and checked the output of the sensors. I was able to see the output was good, but I was unable to see the changes on the Jake or cruise switches.
“I then hooked up ESA – a Paccar program for cab-based system diagnostics – and was able to monitor all the switches and see that they were functioning, but I was unable to use a simulation to make the gauges move.
“Finally, it clicked that I was talking to the cab controller and it was talking back, but nothing else could see it. So, I scoped it. Messages were really funny looking, as there was some pretty severe voltage droop going on.
“Then I remembered the Qualcomm was also down. I decided to see if they were related. I unplugged the MAS (mobile application server) from the truck and it was like a light switch. The messages cleaned up and the truck was back to normal.
“The MAS had an internal failure, causing mass havoc along the J1939. I replaced the MAS and fixed the truck.
“This all happened on a Friday. Ordinarily, I would have waited until Monday to send the truck to the dealer, then waited three days for them to send it back either unfixed or fixed. Then the truck would be down another two days while the MAS was replaced and re-uploaded.
“Instead, it was only down until Monday while waiting for the home office to resend the vehicle data to the new MAS.”
George Arrants is director of training and recruitment for the WheelTime Network (www.wheeltime.com), North America’s largest dedicated service and parts network for quality truck and coach care, and its WheelTime University (WTU). WTU provides assessments, training and ASE (Automotive Service Excellence) test preparation for WheelTime member technicians and fleets that may not have their own training program. As an Automotive Education Consultant specializing in National Automotive Technicians Education Foundation (NATEF)/ASE Accreditation, Arrants works with instructors and administrators to develop partnerships with local business and industry through program advisory committees. These committees help schools establish, develop and maintain programs that are relevant to the needs of automotive, medium and heavy duty and collision industries and the community. He chairs the Technology and Maintenance Council’s TMCSuperTech – the National Technician Skills Competition – and the TMCFutureTech – the National Student Technician Competition. His entire career has been in the automotive service and education industries.
