ANALYSIS
Using Vehicle Diagnostics to Drive Maintenance Programs
WRITTEN BY JOHN WHELAN V
ehicle diagnostics are one of the most important tools we have in our fleet to enable us to keep up with technology and to properly troubleshoot fault codes. One of the priorities in our main-
tenance plan is to be proactive in preventing breakdowns. Transporting students safely is a huge incentive to find ways to avoid problems on the road. With that said, vehicle diagnostics has helped drive our maintenance program by providing us with engine codes that tell us in detail the description of the code, what caused it and how it will affect vehicle operation. With this information at hand, we can look ahead and easily change maintenance procedures to avoid drivability problems.
DEALING WITH EMISSION CODES
Emission codes are a regular occurrence in our bus fleet, and the parameters that set these codes are extremely tight. Usually, when there is an emission code, the engine control unit de-rates the engine (a reduction in power) to protect it from possible damage. A hot exhaust code tells us there could be a build-up of soot inside the diesel particulate filter (DPF). Te first step we do is to perform a parked regeneration using the diagnostic software. Te bus is parked out of the way in the middle of our yard. We hook up the diagnostic software and force a parked regeneration to begin. Te exhaust tempera- tures rise up to 1,000 degrees and combine with a diesel oxidation catalyst to remove harmful particulates. Tis method works, but sometimes the build-up of soot
may have developed during a long period of time, so it isn’t going to go away without a fight. In our fleet, we replace the DPF every 75,000 miles, or 125,000 kilometers. Troughout time, the build-up of particulates is too overwhelming and replacement is required.
REGULAR MAINTENANCE PROCEDURES REDUCE DIESEL EMISSION CODES
To reduce DPF replacement, we perform a parked regen-
eration every oil change at 9,000 miles (15,000 km). We feel this will assist the on-road computer regeneration process and extend the life of the DPF, causing less codes to occur. We also use a low-ash, semi-synthetic engine oil, which helps cut down on emission particulates. (Note: OEM recommendations specify a higher mileage before
changing oil, but the cost of oil compared to possibly increasing soot contamination of the emission system makes this decision justifiable in our operation.)
WATER IN FUEL ENGINE CODE PROMOTES PROPER FUEL FILTER MAINTENANCE
One code not to be forgotten is the “water in fuel” code
that is closely monitored by vehicle diagnostics. Water in the fuel is one of the worst things that could happen to any diesel fuel-injection system. As far as preventive mainte- nance goes, changing fuel filters at the specified mileage is one of the most important steps to carry out with any service routine.
AN ESSENTIAL TOOL FOR SENSOR, WIRING FAILURES
Sensor failures happen as well, and one huge advantage of having vehicle diagnostics is the ability to determine the cause of the code, be it the wiring or a sensor. When we read a code, the diagnostic software guides us to the next step, which describes the code in detail. Having the ability to link up and read data from vehicle
operating systems is extremely valuable. If we have a reoc- curring problem in this area, we start a campaign to check the sensor or wiring during every service to avoid failure. It’s easy to plan ahead and deter an unexpected problem in our fleet using vehicle diagnostics.
Whelan is a school bus and truck mechanic with 34 years of experience. He is currently shop foreman for the School District No. 73 transportation department in Kamloops, British Columbia. He can be reached at
jewhelan58@gmail.com.
“One code not to be forgotten is the ‘water in fuel’ code that is closely monitored by vehicle diagnostics. Water in the fuel is one of the worst things that could happen to any diesel fuel-injection system.”
64 School Transportation News March 2014
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